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Intravenous Vitamin C (PDQ®)–Health Professional Version

Overview

Go to Patient Version

This cancer information summary provides an overview of the use of intravenous (IV) vitamin C (also known as ascorbate or L-ascorbic acid) as a treatment for people with cancer. This summary includes a brief history of early clinical trials of the use of IV vitamin C; reviews of laboratory, animal, and human studies; and current clinical trials.

This summary contains the following key information:

  • Vitamin C is an essential nutrient with redox functions at normal physiologic concentrations.
  • Case series and observational studies from the 1970s of cancer patients who received IV vitamin C seemed to indicate a clinical benefit.
  • Two early randomized placebo-controlled trials that used oral vitamin C (10 g/d) without IV vitamin C noted no significant differences between ascorbate-treated and placebo-treated groups for symptoms, performance status, or survival.
  • Laboratory studies have reported that IV vitamin C has redox properties and decreased cell proliferation in prostate, pancreatic, hepatocellular, colon, mesothelioma, and neuroblastoma cell lines.
  • IV vitamin C has been generally well tolerated in clinical trials.
  • IV administration of vitamin C of doses over 500 mg produces much higher blood concentrations of ascorbate than oral administration of the same dose.
  • The use of IV vitamin C alone as ascorbate versus ascorbate formulations plus certain standard cancer therapies have been shown to be well tolerated in clinical trials.
  • Two studies that used IV vitamin C in cancer patients reported improved quality of life and decreases in cancer-related toxicities.
  • Although early observations from preclinical and clinical trials of IV vitamin C with and without conventional cancer therapies appear promising and the therapy well tolerated, these studies have several limitations due to lack of rigor in trial design.

Many of the medical and scientific terms used in this summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts. When a linked term is clicked, a definition will appear in a separate window.

Reference citations in some PDQ cancer information summaries may include links to external websites that are operated by individuals or organizations for the purpose of marketing or advocating the use of specific treatments or products. These reference citations are included for informational purposes only. Their inclusion should not be viewed as an endorsement of the content of the websites, or of any treatment or product, by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board or the National Cancer Institute.

General Information

Vitamin C is an essential nutrient that has redox functions, is a cofactor for several enzymes, and plays an important role in the synthesis of collagen.[1] A severe deficiency in vitamin C results in scurvy, which is associated with malaise, lethargy, easy bruising, and spontaneous bleeding.[2] One of the effects of scurvy is a change in collagen structure to a thinner consistency. Normal consistency is achieved with administration of vitamin C.

In the mid-20th century, a study hypothesized that cancer may be related to changes in connective tissue, which may be a consequence of vitamin C deficiency.[3] A review of evidence published in 1974 suggested that high-dose ascorbic acid may increase host resistance and be a potential cancer therapy.[4]

Vitamin C is synthesized from D-glucose or D-galactose by many plants and animals. However, humans lack the enzyme L-gulonolactone oxidase required for ascorbic acid synthesis and must obtain vitamin C through food or supplements.[1]

Some companies distribute vitamin C as dietary supplements. In the United States, dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as a separate category from foods, cosmetics, and drugs. Unlike drugs, dietary supplements do not require premarket evaluation and approval by the FDA unless specific disease prevention or treatment claims are made. The quality and amount of ingredients in dietary supplements are also regulated by the FDA through Good Manufacturing Practices (GMPs). The FDA GMPs requires that every finished batch of dietary supplement meets each product specification for identity, purity, strength, composition, and limits on contamination that may adulterate dietary supplements. Because dietary supplements are not formally reviewed for manufacturing consistency every year, ingredients may vary considerably from lot to lot and there is no guarantee that ingredients claimed on product labels are present (or are present in the specified amounts). The FDA has not approved the use of high-dose vitamin C as a treatment for cancer.

References
  1. Naidu KA: Vitamin C in human health and disease is still a mystery? An overview. Nutr J 2: 7, 2003. [PUBMED Abstract]
  2. Padayatty S, Espey MG, Levine M: Vitamin C. In: Coates PM, Betz JM, Blackman MR, et al., eds.: Encyclopedia of Dietary Supplements. 2nd ed. Informa Healthcare, 2010, pp 821-31.
  3. McCORMICK WJ: Cancer: a collagen disease, secondary to a nutritional deficiency. Arch Pediatr 76 (4): 166-71, 1959. [PUBMED Abstract]
  4. Cameron E, Pauling L: The orthomolecular treatment of cancer. I. The role of ascorbic acid in host resistance. Chem Biol Interact 9 (4): 273-83, 1974. [PUBMED Abstract]

History

The earliest experience of using both oral and intravenous (IV) vitamin C for cancer treatment was by a Scottish surgeon, Ewan Cameron, and his colleague, Allan Campbell, in the 1970s.[1] This work led to a collaboration between Cameron and the Nobel Prize–winning chemist Linus Pauling, further promoting the potential of vitamin C therapy in cancer management.[2,3] As a result, two clinical trials of oral vitamin C were conducted in the late 1970s and early 1980s.[4,5] These two trials did not use IV vitamin C.

For more information about these early studies, see the Human Studies section.

Pharmacokinetic studies later revealed substantial differences in the maximum achieved blood concentrations of vitamin C based on the route of administration. When vitamin C is taken orally, plasma concentrations of the vitamin are tightly controlled, with a peak achievable concentration less than 300 µM. However, this tight control is bypassed with IV administration of the vitamin, resulting in very high levels of vitamin C plasma concentration (i.e., levels up to 20 mM).[6,7] Further research suggests that pharmacological concentrations of ascorbate, such as those achieved with IV administration, may result in cell death in many cancer cell lines.[8]

Health care practitioners attending complementary and alternative medicine conferences in 2006 and 2008 were surveyed about usage of high-dose IV vitamin C in patients. Of the 199 total respondents, 172 had administered vitamin C to patients. In general, IV vitamin C was commonly used to treat infections, cancer, and fatigue.[9]

References
  1. Cameron E, Campbell A: The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem Biol Interact 9 (4): 285-315, 1974. [PUBMED Abstract]
  2. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 73 (10): 3685-9, 1976. [PUBMED Abstract]
  3. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: reevaluation of prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 75 (9): 4538-42, 1978. [PUBMED Abstract]
  4. Creagan ET, Moertel CG, O'Fallon JR, et al.: Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. N Engl J Med 301 (13): 687-90, 1979. [PUBMED Abstract]
  5. Moertel CG, Fleming TR, Creagan ET, et al.: High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. N Engl J Med 312 (3): 137-41, 1985. [PUBMED Abstract]
  6. Padayatty SJ, Sun H, Wang Y, et al.: Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 140 (7): 533-7, 2004. [PUBMED Abstract]
  7. Hoffer LJ, Levine M, Assouline S, et al.: Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 19 (11): 1969-74, 2008. [PUBMED Abstract]
  8. Verrax J, Calderon PB: Pharmacologic concentrations of ascorbate are achieved by parenteral administration and exhibit antitumoral effects. Free Radic Biol Med 47 (1): 32-40, 2009. [PUBMED Abstract]
  9. Padayatty SJ, Sun AY, Chen Q, et al.: Vitamin C: intravenous use by complementary and alternative medicine practitioners and adverse effects. PLoS One 5 (7): e11414, 2010. [PUBMED Abstract]

Laboratory/Animal/Preclinical Studies

In Vitro Studies

Numerous studies have demonstrated that supraphysiologic concentrations of ascorbic acid (0.1–100 mM) decrease cell proliferation in a variety of cancer cell lines.[1-5] Specifically, decreases in cell proliferation after ascorbic acid treatment have been reported for prostate,[6] pancreatic,[7,8] hepatocellular,[9] colon,[10] mesothelioma,[11] and neuroblastoma [12] cell lines.

The potential mechanisms through which treatment with pharmacological doses of ascorbic acid may exert its effects on cancer cells have been extensively investigated. Several studies have demonstrated that the in vitro direct cytotoxic effect of ascorbic acid on various types of cancer cells is mediated through a chemical reaction that generates hydrogen peroxide.[1,7,13,14] Treating colon cancer cells with 2 mM to 3 mM of ascorbic acid resulted in downregulation of specificity protein (Sp) transcription factors, iron metabolism disruption, and Sp-regulated genes involved in cancer progression.[10,15] One study suggested that ascorbate-mediated prostate cancer cell death may occur through activation of an autophagy pathway.[6] Data from a 2018 study demonstrated that labile iron and hydrogen peroxide play important roles in the mechanisms of selective toxicity of ascorbate and induction of oxidative DNA damage/cancer cell death.[16] Another in vitro study found that ascorbic acid killed colorectal cancer cells with KRAS or BRAF mutations by inhibiting the enzyme glyceraldehyde 3-phosphate dehydrogenase.[17]

Differences in chemosensitivity to ascorbate treatment in breast cancer cell lines may depend on expression of the sodium-dependent vitamin C transporter 2 (SVCT-2).[18]

Research has suggested that pharmacological doses of ascorbic acid enhance the effects of the following:

Findings from one study reported in 2012 suggested that high-dose ascorbate increases radiosensitivity of glioblastoma multiforme cells, resulting in more cell death than from radiation alone.[21]

However, not all studies combining vitamin C with chemotherapy have shown improved outcomes. Treating leukemia and lymphoma cells with dehydroascorbic acid (the oxidized form of vitamin C that increases levels of intracellular ascorbic acid) reduced the cytotoxic effects of various antineoplastic agents tested, including doxorubicin, methotrexate, and cisplatin (relative reductions in cytotoxicity ranged from 30% to 70%).[22] In another study, multiple myeloma cells were treated with bortezomib and/or plasma obtained from healthy volunteers who had taken oral vitamin C supplements. Cells treated with a combination of bortezomib and volunteers’ plasma exhibited lower cytotoxicity than did cells treated with bortezomib alone.[23]

Animal Studies

Using oral N-acetylcysteine and vitamin C, researchers showed in 2007 that these compounds, both thought to act predominantly as antioxidants, may have antitumorigenic actions in vivo by decreasing levels of hypoxia-inducible factor-1, a transcription factor that targets vascular endothelial growth factor and plays a role in angiogenesis.[24]

Studies have demonstrated tumor growth inhibition after treatment with pharmacological ascorbate in animal models with the following:

The effects of parenterally administered ascorbic acid in combination with standard treatments on tumors have been investigated. In a mouse model of pancreatic cancer, the combination of gemcitabine (30 or 60 mg/kg every 4 days) and intraperitoneal injection of ascorbate (4 g/kg daily) resulted in greater decreases in tumor volume and weight, compared with gemcitabine treatment alone.[8] A study of mouse models of ovarian cancer found that ascorbate enhanced the tumor inhibitory effect of carboplatin and paclitaxel, first-line chemotherapy used in ovarian cancer.[27] One study working with xenograft models of non-small cell lung cancer and glioblastoma multiforme showed that the combination of chemotherapy (carboplatin for lung cancer and temozolomide for glioblastoma), radiation therapy, and pharmacologic ascorbate (4 g/kg/d) intraperitoneal injection resulted in prolonged survival compared with just the combination of chemotherapy and radiation therapy.[15]

A study explored the efficacy of parenterally injected ascorbate with gemcitabine or radiation treatment in a mouse sarcoma xenograft model. Treatment involved intraperitoneally administered doses of ascorbate (4 g/kg) combined with gemcitabine (60 mg/kg) or radiation therapy (12 Gy in 2 fractions). Compared with the control group, the combination treatments produced significantly greater inhibition of tumor growth, greater survival rate, and no increase in toxicity, suggesting cancer cell selective toxicity.[16]

There have also been reports of animal studies in which vitamin C has interfered with the anticancer activity of various drugs. In a study reported in 2008, administration of dehydroascorbic acid to lymphoma-xenograft mice prior to doxorubicin treatment resulted in significantly larger tumors than did treatment with doxorubicin alone.[22] Notably, this study used dehydroascorbate, the oxidized form of vitamin C that is known to be transported actively into cells and then reduced to vitamin C, but is not routinely used. Treating multiple myeloma xenograft mice with a combination of oral vitamin C and bortezomib resulted in significantly greater tumor volume than did treatment with bortezomib alone.[23] This increase in tumor volume was caused by a chemical reaction that occurs in the gastrointestinal tract but does not appear to be relevant to intravenous administration.

References
  1. Chen P, Stone J, Sullivan G, et al.: Anti-cancer effect of pharmacologic ascorbate and its interaction with supplementary parenteral glutathione in preclinical cancer models. Free Radic Biol Med 51 (3): 681-7, 2011. [PUBMED Abstract]
  2. Chen Q, Espey MG, Krishna MC, et al.: Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. Proc Natl Acad Sci U S A 102 (38): 13604-9, 2005. [PUBMED Abstract]
  3. Verrax J, Calderon PB: Pharmacologic concentrations of ascorbate are achieved by parenteral administration and exhibit antitumoral effects. Free Radic Biol Med 47 (1): 32-40, 2009. [PUBMED Abstract]
  4. Chen Q, Espey MG, Sun AY, et al.: Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A 105 (32): 11105-9, 2008. [PUBMED Abstract]
  5. Frömberg A, Gutsch D, Schulze D, et al.: Ascorbate exerts anti-proliferative effects through cell cycle inhibition and sensitizes tumor cells towards cytostatic drugs. Cancer Chemother Pharmacol 67 (5): 1157-66, 2011. [PUBMED Abstract]
  6. Chen P, Yu J, Chalmers B, et al.: Pharmacological ascorbate induces cytotoxicity in prostate cancer cells through ATP depletion and induction of autophagy. Anticancer Drugs 23 (4): 437-44, 2012. [PUBMED Abstract]
  7. Du J, Martin SM, Levine M, et al.: Mechanisms of ascorbate-induced cytotoxicity in pancreatic cancer. Clin Cancer Res 16 (2): 509-20, 2010. [PUBMED Abstract]
  8. Espey MG, Chen P, Chalmers B, et al.: Pharmacologic ascorbate synergizes with gemcitabine in preclinical models of pancreatic cancer. Free Radic Biol Med 50 (11): 1610-9, 2011. [PUBMED Abstract]
  9. Lin ZY, Chuang WL: Pharmacologic concentrations of ascorbic acid cause diverse influence on differential expressions of angiogenic chemokine genes in different hepatocellular carcinoma cell lines. Biomed Pharmacother 64 (5): 348-51, 2010. [PUBMED Abstract]
  10. Pathi SS, Lei P, Sreevalsan S, et al.: Pharmacologic doses of ascorbic acid repress specificity protein (Sp) transcription factors and Sp-regulated genes in colon cancer cells. Nutr Cancer 63 (7): 1133-42, 2011. [PUBMED Abstract]
  11. Takemura Y, Satoh M, Satoh K, et al.: High dose of ascorbic acid induces cell death in mesothelioma cells. Biochem Biophys Res Commun 394 (2): 249-53, 2010. [PUBMED Abstract]
  12. Hardaway CM, Badisa RB, Soliman KF: Effect of ascorbic acid and hydrogen peroxide on mouse neuroblastoma cells. Mol Med Report 5 (6): 1449-52, 2012. [PUBMED Abstract]
  13. Du J, Cullen JJ, Buettner GR: Ascorbic acid: chemistry, biology and the treatment of cancer. Biochim Biophys Acta 1826 (2): 443-57, 2012. [PUBMED Abstract]
  14. Levine M, Padayatty SJ, Espey MG: Vitamin C: a concentration-function approach yields pharmacology and therapeutic discoveries. Adv Nutr 2 (2): 78-88, 2011. [PUBMED Abstract]
  15. Schoenfeld JD, Sibenaller ZA, Mapuskar KA, et al.: O2⋅- and H2O2-Mediated Disruption of Fe Metabolism Causes the Differential Susceptibility of NSCLC and GBM Cancer Cells to Pharmacological Ascorbate. Cancer Cell 32 (2): 268, 2017. [PUBMED Abstract]
  16. Schoenfeld JD, Sibenaller ZA, Mapuskar KA, et al.: Redox active metals and H2O2 mediate the increased efficacy of pharmacological ascorbate in combination with gemcitabine or radiation in pre-clinical sarcoma models. Redox Biol 14: 417-422, 2018. [PUBMED Abstract]
  17. Yun J, Mullarky E, Lu C, et al.: Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH. Science 350 (6266): 1391-6, 2015. [PUBMED Abstract]
  18. Hong SW, Lee SH, Moon JH, et al.: SVCT-2 in breast cancer acts as an indicator for L-ascorbate treatment. Oncogene 32 (12): 1508-17, 2013. [PUBMED Abstract]
  19. Ong PS, Chan SY, Ho PC: Differential augmentative effects of buthionine sulfoximine and ascorbic acid in As2O3-induced ovarian cancer cell death: oxidative stress-independent and -dependent cytotoxic potentiation. Int J Oncol 38 (6): 1731-9, 2011. [PUBMED Abstract]
  20. Martinotti S, Ranzato E, Burlando B: In vitro screening of synergistic ascorbate-drug combinations for the treatment of malignant mesothelioma. Toxicol In Vitro 25 (8): 1568-74, 2011. [PUBMED Abstract]
  21. Herst PM, Broadley KW, Harper JL, et al.: Pharmacological concentrations of ascorbate radiosensitize glioblastoma multiforme primary cells by increasing oxidative DNA damage and inhibiting G2/M arrest. Free Radic Biol Med 52 (8): 1486-93, 2012. [PUBMED Abstract]
  22. Heaney ML, Gardner JR, Karasavvas N, et al.: Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Res 68 (19): 8031-8, 2008. [PUBMED Abstract]
  23. Perrone G, Hideshima T, Ikeda H, et al.: Ascorbic acid inhibits antitumor activity of bortezomib in vivo. Leukemia 23 (9): 1679-86, 2009. [PUBMED Abstract]
  24. Gao P, Zhang H, Dinavahi R, et al.: HIF-dependent antitumorigenic effect of antioxidants in vivo. Cancer Cell 12 (3): 230-8, 2007. [PUBMED Abstract]
  25. Pollard HB, Levine MA, Eidelman O, et al.: Pharmacological ascorbic acid suppresses syngeneic tumor growth and metastases in hormone-refractory prostate cancer. In Vivo 24 (3): 249-55, 2010 May-Jun. [PUBMED Abstract]
  26. Yeom CH, Lee G, Park JH, et al.: High dose concentration administration of ascorbic acid inhibits tumor growth in BALB/C mice implanted with sarcoma 180 cancer cells via the restriction of angiogenesis. J Transl Med 7: 70, 2009. [PUBMED Abstract]
  27. Ma Y, Chapman J, Levine M, et al.: High-dose parenteral ascorbate enhanced chemosensitivity of ovarian cancer and reduced toxicity of chemotherapy. Sci Transl Med 6 (222): 222ra18, 2014. [PUBMED Abstract]

Human/Clinical Studies

Early Case Series Studies and Clinical Trials With Ascorbate Only

In the early 1970s, a consecutive case series was conducted in which 50 patients with advanced cancer were treated with intravenous (IV) and oral doses of ascorbic acid.[1] These patients began ascorbic acid treatment after conventional therapies were deemed unlikely to be effective. Patients received IV ascorbic acid (10 g/day for 10 consecutive days; some patients received higher doses), oral ascorbic acid (10 g/day), or both. The patients exhibited a wide variety of responses to treatment, including the following:

However, the authors noted that lack of controls prevented definitive assignment of any beneficial responses to the ascorbic acid treatment.[1] A case report published in 1975 detailed one of the patients who had experienced tumor regression.[2] Diagnosed with reticulum cell sarcoma, the patient exhibited improvement in well-being and resolution of lung masses after being treated with IV and oral ascorbic acid. When the patient's daily dose of ascorbic acid was reduced, some of signs of the disease returned; however, remission was achieved again after the patient reverted to the higher initial dose.

A larger case series of terminal cancer patients treated with ascorbate was reported in 1976. In this study, 100 terminal cancer patients (50 of whom were reported on previously) [1] were treated with ascorbate (10 g/day for 10 days IV, then orally) and compared with 1,000 matched controls from the same hospital. The mean survival time for ascorbate-treated patients was 300 days longer than that of the matched controls.[3,4]

Two studies tried to reproduce earlier results. These studies were randomized, placebo-controlled trials in which cancer patients received either 10 g of oral vitamin C or placebo daily until signs of cancer progression. No IV vitamin C was given in these studies. At the end of each study, no significant differences were noted between the two ascorbate-treated and placebo-treated groups for symptoms, performance status, or survival.[5,6]

Recent Case Series Studies and Clinical Trials With Ascorbate Only

One study reported three case reports of cancer patients who received IV vitamin C as their main therapy. During vitamin C therapy, the patients used additional treatments, including vitamins, minerals, and botanicals. According to the authors, the cases were reviewed in accordance with the NCI Best Case Series guidelines. Histopathologic examination suggested poor prognoses for these patients, but they had long survival times after being treated with IV vitamin C.[7] Vitamin C was given at doses ranging from 15 g to 65 g, initially once or twice a week for several months; two patients then received it less frequently for 1 to 4 years.

One study demonstrated that IV vitamin C treatment resulted in improved quality of life and a decrease in cancer-related side effects in cancer patients.[8]

A single-arm pilot study of weekly infusions of 60 g of ascorbic acid for 9 weeks in castration-resistant prostate cancer patients failed to observe a reduction in serum prostate-specific antigen or tumor regression.[9]

Studies have shown that vitamin C can be safely administered to healthy volunteers or cancer patients at doses up to 1.5 g/kg and with screening to eliminate treating individuals with risk factors for toxicity (e.g., glucose-6-phosphate dehydrogenase deficiency, renal diseases, or urolithiasis). These studies have also found that plasma concentrations of vitamin C are higher with IV administration than with oral administration and are maintained for more than 4 hours.[10,11]

Early Phase Ascorbate Trials Combined With Standard Cancer Therapies

A phase I study published in 2012 examined the safety and efficacy of combining IV ascorbate with gemcitabine and erlotinib in patients with stage IV pancreatic cancer. Fourteen patients entered the study and planned to receive IV gemcitabine (1,000 mg/m2 over 30 minutes, once a week for 7 weeks), oral erlotinib (100 mg daily for 8 weeks), and IV ascorbate (50 g/infusion, 75 g/infusion, or 100 g/infusion 3 times per week for 8 weeks). Minimal adverse effects were reported for ascorbic acid treatment. Five patients received fewer than 18 of the planned 24 ascorbate infusions and thus did not have follow-up imaging to assess response. Three of those patients had clinically determined progressive disease. All of the other nine patients had repeat imaging to assess tumor size, and each met the criteria for having stable disease.[12]

A 2013 phase I clinical study (NCT01049880) evaluated the safety of combining pharmacological ascorbate with gemcitabine in treating patients with stage IV pancreatic cancer. During each 4-week cycle, patients received gemcitabine weekly for 3 weeks (1,000 mg/m2 over 30 minutes) and twice-weekly ascorbate infusions for 4 weeks (15 g over 30 minutes during the first week, followed by weekly escalations in dose until plasma levels reached at least 350 mg/dL [20 mM]). Among nine patients, mean progression-free survival was 26 weeks and overall survival was 12 months. The combination treatment was well tolerated, and no significant adverse events were reported.[13]

In 2014, a phase I/IIA clinical trial evaluated the toxicities of combining IV ascorbate with carboplatin and paclitaxel in stage III/IV ovarian cancer. Twenty-seven patients were randomly assigned to receive either chemotherapy alone or chemotherapy and IV vitamin C concurrently. Chemotherapy was given for 6 months, and IV vitamin C was given for 12 months. The addition of IV vitamin C was associated with reduced chemotherapy-related toxicities.[14]

A 2015 phase I/II clinical trial of high-dose IV vitamin C (approximately 1.5 g/kg body weight) combined with various chemotherapies, depending on the specific cancer diagnosis, was conducted to do the following:[15]

  • Observe the associated adverse events.
  • Assess the pharmacokinetic profiles of vitamin C and oxalic acid levels prechemotherapy- and postchemotherapy.
  • Assess clinical responses.
  • Assess changes in mood.
  • Assess changes in quality of life.

High-dose IV vitamin C was analyzed in 14 patients and was generally well tolerated and safe. Minor temporary adverse effects included increased urinary flow, thirst, nausea, vomiting, and chills, some of which could be prevented. Chemotherapy administration did not affect the plasma concentration of vitamin C. Although a few patients experienced temporary stable disease, functional improvement, and increased energy, the sample size is so small that the generalizability of these results is uncertain.[15]

In 2017, a phase I/IIA study reported using IV vitamin C with standard-of-care gemcitabine chemotherapy in patients with newly diagnosed pancreatic cancer.[16] Seven participants were initially enrolled. When safety was confirmed, an additional seven participants were enrolled. Twelve of the 14 enrolled participants completed the phase I pharmacokinetic evaluation. The evaluation consisted of IV vitamin C and gemcitabine pharmacokinetic measurements, each as single drugs, and then followed by the pharmacokinetic measurement of IV vitamin C combined with gemcitabine. IV vitamin C administration did not interfere with gemcitabine.

In May 2019, a phase I study was published that examined the safety, pharmacokinetics, and efficacy of high-dose IV vitamin C combined with the combination chemotherapy regimens mFOLFOX6 (oxaliplatin + leucovorin + fluorouracil) or FOLFIRI (leucovorin + fluorouracil + irinotecan hydrochloride). This study consisted of 36 patients with metastatic colorectal cancer or gastric cancer. The main goal was to determine the maximum-tolerated dose and the recommended phase II dose of ascorbic acid with coadministration of either mFOLFOX6 or FOLFIRI. Patients received chemotherapy treatment on a 14-day cycle with vitamin C infusions occurring for 3 consecutive days for 3 hours at a time. For the dose-escalation portion of the study, ascorbic acid doses ranged from 0.2 g/kg to 1.5 g/kg. To determine the optimal administration rate of ascorbic acid, patient cohorts received infusion rates set at 0.6 g/min, 0.8 g/min, or 1 g/min. The study showed no dose-limiting toxicity for all doses and dosing rates; thus a maximum-tolerated dose was not reached, leading to a recommended phase II dose of 1.5 g/kg for ascorbic acid. Overall, no severe adverse reactions occurred, and the treatments were deemed safe and tolerable. A randomized phase III trial (NCT02969681) is being conducted to determine the clinical efficacy of ascorbic acid with mFOLFOX6 with or without bevacizumab in patients with metastatic colorectal cancer.[17]

Table 1. Clinical Studies of Ascorbate with Chemotherapya
ReferenceTrial DesignCondition or Cancer TypeDoseTreatment Groups (Enrolled; Treated; Placebo or No Treatment Control)bResultsConcurrent Therapy UsedLevel of Evidence Scorec
 
aFor additional information and definition of terms, see text and the NCI Dictionary of Cancer Terms.
bNumber of patients treated plus number of patient controls may not equal number of patients enrolled; number of patients enrolled equals number of patients initially recruited/considered by the researchers who conducted a study; number of patients treated equals number of enrolled patients who were given the treatment being studied AND for whom results were reported.
cFor information about levels of evidence analysis and scores, see Levels of Evidence for Human Studies of Integrative, Alternative, and Complementary Therapies.
[16]Phase I/IIA trialNewly diagnosed pancreatic cancer 6 doses of 25–75 g/infusion for phase I and 64 doses of 100 g/infusion for phase II14; 12; noneAscorbic acid did not interfere with gemcitabine pharmacokineticsGemcitabine2Dii
[12]Phase I, open label trialMetastatic stage IV pancreatic cancer50 g/infusion, 75 g/infusion, or 100 g/infusion 3x/wk for 8 wk14; 14 (9 analyzed); noneAscorbic acid was well tolerated with gemcitabine and erlotinibGemcitabine, erlotinib2Dii
[13]Phase I, open label trialStage IV pancreatic adenocarcinoma15 g/wk until the plasma level reached at least 350 mg/dL (20 mM) 15; 11 (9 completed); noneAscorbate acid was well tolerated with gemcitabineGemcitabine2Dii
[14]Pilot phase I/IIA trialStage III/IV ovarian cancerUp to 75 g or 100 g 2x/wk for 12 mo 27; 14 (chemotherapy), 13 (chemotherapy and intravenous vitamin C); noneAscorbate acid added to carboplatin and paclitaxel therapy reduced chemotherapy-related toxicitiesCarboplatin, paclitaxel2C

Trials of high-dose IV vitamin C combined with other drugs are ongoing.[12,14] A number of studies have included small doses of IV ascorbic acid treatment (1,000 mg) with arsenic trioxide regimens, with mixed results. For study results, see Table 2.

Table 2. Clinical Studies of Ascorbate in Arsenic Trioxide–Containing Regimensa
ReferenceTrial Design Condition or Cancer TypeDoseTreatment Groups (Enrolled; Treated; Placebo or No Treatment Control)bResultsConcurrent Therapy Used Level of Evidence Scorec
N = number of patients; RCT = randomized controlled trial.
aFor additional information and definition of terms, see text and the NCI Dictionary of Cancer Terms.
bNumber of patients treated plus number of patient controls may not equal number of patients enrolled; number of patients enrolled equals number of patients initially recruited/considered by the researchers who conducted a study; number of patients treated equals number of enrolled patients who were given the treatment being studied AND for whom results were reported.
cFor information about levels of evidence analysis and scores, see Levels of Evidence for Human Studies of Integrative, Alternative, and Complementary Therapies.
[18]RCT Multiple myeloma1,000 mg48; arm 1 (N = 16), arm 2 (N = 17), arm 3 (N = 15); noneThe addition of arsenic trioxide and ascorbic acid to high-dose melphalan was reported safe and well toleratedMelphalan1iiDii
[19]Phase II, open labelRelapsed or refractory multiple myeloma1,000 mg20; 20; noneClinical efficacy and tolerability with arsenic trioxide, dexamethasone, and ascorbic acid was reported Dexamethasone3Dii
[20]Phase I/II, open labelRelapsed or refractory multiple myeloma1,000 mg22; 22; noneArsenic trioxide, bortezomib, and ascorbic acid was well tolerated with signs of clinical efficacy Bortezomib3Dii
[21]Phase IIRelapsed or refractory multiple myeloma1,000 mg65; 65; noneMelphalan, arsenic trioxide, and ascorbic acid was effective and well tolerated Melphalan3Dii
[22]Phase IIRefractory metastatic colorectal carcinoma1,000 mg5; 5; nonePatients developed moderate to severe toxic side effects without clinical responseNone3Dii
[23]Phase II, open labelMetastatic melanoma1,000 mg11; 10; nonePatients developed toxic side effects without clinical responseTemozolomide 3Dii

Informed by their preclinical data,[19] researchers at the University of Iowa treated patients with non-small cell lung carcinoma (NSCLC) and glioblastoma multiforme (GBM) in two pilot clinical trials (NCT02420314 and NCT01752491).[24] Participants in both trials were given conventional therapy plus IV vitamin C, with dosing individualized to achieve a 20 mM peak plasma concentration of ascorbate in each patient. The GBM study was a phase I design with 13 total patients. IV vitamin C was given with both radiation therapy and temozolomide and toxicity, progression-free survival, and overall survival all compared favorably to the outcomes of historical controls. The NSCLC trial was a phase II design of 14 patients with advanced cancer who received both chemotherapy and IV vitamin C (median maximum plasma concentration, 16.4 mM). The disease control and confirmed objective response rates of the study group again compared favorably with those of historical controls. Limitations of these studies included the use of historical controls and small numbers of enrolled participants.

Various trials of high-dose IV vitamin C with other drugs are ongoing. There are currently five trials being conducted by researchers at the University of Iowa; four phase II studies and one phase IB/II study. The four phase II clinical trials are investigating the efficacy of high-dose ascorbate combined with standard anticancer regimens. The studies are exploring the combination of high-dose ascorbate with the following:

Another phase IB/II trial (NCT03508726) is studying the safety and efficacy of high-dose ascorbate with preoperative radiation therapy in locally advanced soft tissue sarcoma patients.

Several studies have included IV ascorbic acid treatment at a fixed dose of 1,000 mg with arsenic trioxide regimens, with mixed results. Researchers using this approach suggested that the pro-oxidant properties of IV ascorbic acid may have helped to increase the effects of arsenic trioxide by sensitization of malignant cells to arsenic’s cytotoxic effects.[25] The combination therapies were well tolerated and suggested beneficial effects in multiple myeloma patients, although the specific contribution of vitamin C could not be determined.[18-21] However, similar combination regimens resulted in severe side effects, disease progression, and no anticancer effect in patients with refractory metastatic colorectal cancer [22] and metastatic melanoma.[23] Because these were not placebo-controlled trials, the extent that ascorbate contributed to the toxicity or efficacy demonstrated in these studies is unclear.

Current Clinical Trials

Use our advanced clinical trial search to find NCI-supported cancer clinical trials that are now enrolling patients. The search can be narrowed by location of the trial, type of treatment, name of the drug, and other criteria. General information about clinical trials is also available.

References
  1. Cameron E, Campbell A: The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem Biol Interact 9 (4): 285-315, 1974. [PUBMED Abstract]
  2. Cameron E, Campbell A, Jack T: The orthomolecular treatment of cancer. III. Reticulum cell sarcoma: double complete regression induced by high-dose ascorbic acid therapy. Chem Biol Interact 11 (5): 387-93, 1975. [PUBMED Abstract]
  3. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 73 (10): 3685-9, 1976. [PUBMED Abstract]
  4. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: reevaluation of prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 75 (9): 4538-42, 1978. [PUBMED Abstract]
  5. Creagan ET, Moertel CG, O'Fallon JR, et al.: Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. N Engl J Med 301 (13): 687-90, 1979. [PUBMED Abstract]
  6. Moertel CG, Fleming TR, Creagan ET, et al.: High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. N Engl J Med 312 (3): 137-41, 1985. [PUBMED Abstract]
  7. Padayatty SJ, Riordan HD, Hewitt SM, et al.: Intravenously administered vitamin C as cancer therapy: three cases. CMAJ 174 (7): 937-42, 2006. [PUBMED Abstract]
  8. Yeom CH, Jung GC, Song KJ: Changes of terminal cancer patients' health-related quality of life after high dose vitamin C administration. J Korean Med Sci 22 (1): 7-11, 2007. [PUBMED Abstract]
  9. Nielsen TK, Højgaard M, Andersen JT, et al.: Weekly ascorbic acid infusion in castration-resistant prostate cancer patients: a single-arm phase II trial. Transl Androl Urol 6 (3): 517-528, 2017. [PUBMED Abstract]
  10. Padayatty SJ, Sun H, Wang Y, et al.: Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 140 (7): 533-7, 2004. [PUBMED Abstract]
  11. Hoffer LJ, Levine M, Assouline S, et al.: Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 19 (11): 1969-74, 2008. [PUBMED Abstract]
  12. Monti DA, Mitchell E, Bazzan AJ, et al.: Phase I evaluation of intravenous ascorbic acid in combination with gemcitabine and erlotinib in patients with metastatic pancreatic cancer. PLoS One 7 (1): e29794, 2012. [PUBMED Abstract]
  13. Welsh JL, Wagner BA, van't Erve TJ, et al.: Pharmacological ascorbate with gemcitabine for the control of metastatic and node-positive pancreatic cancer (PACMAN): results from a phase I clinical trial. Cancer Chemother Pharmacol 71 (3): 765-75, 2013. [PUBMED Abstract]
  14. Ma Y, Chapman J, Levine M, et al.: High-dose parenteral ascorbate enhanced chemosensitivity of ovarian cancer and reduced toxicity of chemotherapy. Sci Transl Med 6 (222): 222ra18, 2014. [PUBMED Abstract]
  15. Hoffer LJ, Robitaille L, Zakarian R, et al.: High-dose intravenous vitamin C combined with cytotoxic chemotherapy in patients with advanced cancer: a phase I-II clinical trial. PLoS One 10 (4): e0120228, 2015. [PUBMED Abstract]
  16. Polireddy K, Dong R, Reed G, et al.: High Dose Parenteral Ascorbate Inhibited Pancreatic Cancer Growth and Metastasis: Mechanisms and a Phase I/IIa study. Sci Rep 7 (1): 17188, 2017. [PUBMED Abstract]
  17. Wang F, He MM, Wang ZX, et al.: Phase I study of high-dose ascorbic acid with mFOLFOX6 or FOLFIRI in patients with metastatic colorectal cancer or gastric cancer. BMC Cancer 19 (1): 460, 2019. [PUBMED Abstract]
  18. Qazilbash MH, Saliba RM, Nieto Y, et al.: Arsenic trioxide with ascorbic acid and high-dose melphalan: results of a phase II randomized trial. Biol Blood Marrow Transplant 14 (12): 1401-7, 2008. [PUBMED Abstract]
  19. Abou-Jawde RM, Reed J, Kelly M, et al.: Efficacy and safety results with the combination therapy of arsenic trioxide, dexamethasone, and ascorbic acid in multiple myeloma patients: a phase 2 trial. Med Oncol 23 (2): 263-72, 2006. [PUBMED Abstract]
  20. Berenson JR, Matous J, Swift RA, et al.: A phase I/II study of arsenic trioxide/bortezomib/ascorbic acid combination therapy for the treatment of relapsed or refractory multiple myeloma. Clin Cancer Res 13 (6): 1762-8, 2007. [PUBMED Abstract]
  21. Berenson JR, Boccia R, Siegel D, et al.: Efficacy and safety of melphalan, arsenic trioxide and ascorbic acid combination therapy in patients with relapsed or refractory multiple myeloma: a prospective, multicentre, phase II, single-arm study. Br J Haematol 135 (2): 174-83, 2006. [PUBMED Abstract]
  22. Subbarayan PR, Lima M, Ardalan B: Arsenic trioxide/ascorbic acid therapy in patients with refractory metastatic colorectal carcinoma: a clinical experience. Acta Oncol 46 (4): 557-61, 2007. [PUBMED Abstract]
  23. Bael TE, Peterson BL, Gollob JA: Phase II trial of arsenic trioxide and ascorbic acid with temozolomide in patients with metastatic melanoma with or without central nervous system metastases. Melanoma Res 18 (2): 147-51, 2008. [PUBMED Abstract]
  24. Schoenfeld JD, Sibenaller ZA, Mapuskar KA, et al.: O2⋅- and H2O2-Mediated Disruption of Fe Metabolism Causes the Differential Susceptibility of NSCLC and GBM Cancer Cells to Pharmacological Ascorbate. Cancer Cell 32 (2): 268, 2017. [PUBMED Abstract]
  25. Campbell RA, Sanchez E, Steinberg JA, et al.: Antimyeloma effects of arsenic trioxide are enhanced by melphalan, bortezomib and ascorbic acid. Br J Haematol 138 (4): 467-78, 2007. [PUBMED Abstract]

Adverse Effects

Intravenous (IV) high-dose ascorbic acid has been generally well tolerated in clinical trials.[1-9] Renal failure after ascorbic acid treatment has been reported in patients with preexisting renal disorders.[10] One study reported fluid overload related to ascorbic acid infusion, but this may be caused by the delivery method and not the product.[11]

Case reports have indicated that patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency should not receive high doses of vitamin C because of the risk of developing hemolysis.[12-14]

Administration of IV vitamin C at high doses has been shown to interfere with the measurement of serum biochemical parameters. A study of the administration of high-dose IV vitamin C has been observed to interfere with certain laboratory tests such as strip-based glucose meters, showing false elevations in the glucose measurements.[15,16]

Drug Interactions

When administered in high doses, vitamin C may result in adverse interactions with some anticancer agents. These interactions have primarily been detected in preclinical studies. Two early clinical studies evaluated the safety of combining high-dose IV ascorbate with gemcitabine in patients with stage IV pancreatic cancer. The combination therapy was well tolerated by patients, and no significant adverse events were reported.[9,17]

In vitro and in vivo animal studies have suggested that combining oral vitamin C with bortezomib interferes with the drug’s ability to act as a proteasome inhibitor and blocks bortezomib-initiated apoptosis.[18-20] This interference occurred even with the oral administration of vitamin C (40 mg/kg/day) to animals. Studies in cell culture and performed by adding blood plasma from healthy volunteers given oral vitamin C (1 g/day) also showed a significant decrease in bortezomib’s growth inhibitory effect on multiple myeloma cells. Another study found similar results. Plasma from healthy volunteers who took 1 g of oral vitamin C per day was shown to decrease bortezomib growth inhibition in multiple myeloma cells and to block its inhibitory effect on 20S proteasome activity.[20] However, a study that utilized mice harboring human prostate cancer cell xenografts failed to find any significant effect of oral vitamin C (40 mg/kg/day or 500 mg/kg/day) on the tumor growth inhibitory action of bortezomib.[21] Because IV administration of vitamin C is known to produce higher concentrations of ascorbate than oral administration, these results should be a warning for cancer patients who are receiving treatment with bortezomib. Study results of the co-administration of IV vitamin C and bortezomib in humans would help guide clinical recommendations.

Several studies have been performed to assess the potential synergistic or inhibitory action of vitamin C on certain chemotherapy drugs, with variable results. A series of studies in cell culture and in animals bearing tumors has shown that when given at high concentrations or dosages, dehydroascorbic acid (an oxidized form of vitamin C) can interfere with the cytotoxic effects of several chemotherapy drugs.[22] However, dehydroascorbic acid is generally present only at low concentrations in dietary supplements and fresh foods.

References
  1. Padayatty SJ, Sun H, Wang Y, et al.: Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 140 (7): 533-7, 2004. [PUBMED Abstract]
  2. Hoffer LJ, Levine M, Assouline S, et al.: Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 19 (11): 1969-74, 2008. [PUBMED Abstract]
  3. Chen Q, Espey MG, Sun AY, et al.: Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A 105 (32): 11105-9, 2008. [PUBMED Abstract]
  4. Monti DA, Mitchell E, Bazzan AJ, et al.: Phase I evaluation of intravenous ascorbic acid in combination with gemcitabine and erlotinib in patients with metastatic pancreatic cancer. PLoS One 7 (1): e29794, 2012. [PUBMED Abstract]
  5. Abou-Jawde RM, Reed J, Kelly M, et al.: Efficacy and safety results with the combination therapy of arsenic trioxide, dexamethasone, and ascorbic acid in multiple myeloma patients: a phase 2 trial. Med Oncol 23 (2): 263-72, 2006. [PUBMED Abstract]
  6. Berenson JR, Matous J, Swift RA, et al.: A phase I/II study of arsenic trioxide/bortezomib/ascorbic acid combination therapy for the treatment of relapsed or refractory multiple myeloma. Clin Cancer Res 13 (6): 1762-8, 2007. [PUBMED Abstract]
  7. Qazilbash MH, Saliba RM, Nieto Y, et al.: Arsenic trioxide with ascorbic acid and high-dose melphalan: results of a phase II randomized trial. Biol Blood Marrow Transplant 14 (12): 1401-7, 2008. [PUBMED Abstract]
  8. Ma Y, Chapman J, Levine M, et al.: High-dose parenteral ascorbate enhanced chemosensitivity of ovarian cancer and reduced toxicity of chemotherapy. Sci Transl Med 6 (222): 222ra18, 2014. [PUBMED Abstract]
  9. Polireddy K, Dong R, Reed G, et al.: High Dose Parenteral Ascorbate Inhibited Pancreatic Cancer Growth and Metastasis: Mechanisms and a Phase I/IIa study. Sci Rep 7 (1): 17188, 2017. [PUBMED Abstract]
  10. Padayatty SJ, Sun AY, Chen Q, et al.: Vitamin C: intravenous use by complementary and alternative medicine practitioners and adverse effects. PLoS One 5 (7): e11414, 2010. [PUBMED Abstract]
  11. Nielsen TK, Højgaard M, Andersen JT, et al.: Weekly ascorbic acid infusion in castration-resistant prostate cancer patients: a single-arm phase II trial. Transl Androl Urol 6 (3): 517-528, 2017. [PUBMED Abstract]
  12. Campbell GD, Steinberg MH, Bower JD: Letter: Ascorbic acid-induced hemolysis in G-6-PD deficiency. Ann Intern Med 82 (6): 810, 1975. [PUBMED Abstract]
  13. Mehta JB, Singhal SB, Mehta BC: Ascorbic-acid-induced haemolysis in G-6-PD deficiency. Lancet 336 (8720): 944, 1990. [PUBMED Abstract]
  14. Rees DC, Kelsey H, Richards JD: Acute haemolysis induced by high dose ascorbic acid in glucose-6-phosphate dehydrogenase deficiency. BMJ 306 (6881): 841-2, 1993. [PUBMED Abstract]
  15. Katzman BM, Kelley BR, Deobald GR, et al.: Unintended Consequence of High-Dose Vitamin C Therapy for an Oncology Patient: Evaluation of Ascorbic Acid Interference With Three Hospital-Use Glucose Meters. J Diabetes Sci Technol 15 (4): 897-900, 2021. [PUBMED Abstract]
  16. Martinello F, da Silva EL: Ascorbic acid interference in the measurement of serum biochemical parameters: in vivo and in vitro studies. Clin Biochem 39 (4): 396-403, 2006. [PUBMED Abstract]
  17. Welsh JL, Wagner BA, van't Erve TJ, et al.: Pharmacological ascorbate with gemcitabine for the control of metastatic and node-positive pancreatic cancer (PACMAN): results from a phase I clinical trial. Cancer Chemother Pharmacol 71 (3): 765-75, 2013. [PUBMED Abstract]
  18. Zou W, Yue P, Lin N, et al.: Vitamin C inactivates the proteasome inhibitor PS-341 in human cancer cells. Clin Cancer Res 12 (1): 273-80, 2006. [PUBMED Abstract]
  19. Llobet D, Eritja N, Encinas M, et al.: Antioxidants block proteasome inhibitor function in endometrial carcinoma cells. Anticancer Drugs 19 (2): 115-24, 2008. [PUBMED Abstract]
  20. Perrone G, Hideshima T, Ikeda H, et al.: Ascorbic acid inhibits antitumor activity of bortezomib in vivo. Leukemia 23 (9): 1679-86, 2009. [PUBMED Abstract]
  21. Bannerman B, Xu L, Jones M, et al.: Preclinical evaluation of the antitumor activity of bortezomib in combination with vitamin C or with epigallocatechin gallate, a component of green tea. Cancer Chemother Pharmacol 68 (5): 1145-54, 2011. [PUBMED Abstract]
  22. Heaney ML, Gardner JR, Karasavvas N, et al.: Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Res 68 (19): 8031-8, 2008. [PUBMED Abstract]

Summary of the Evidence for Intravenous Vitamin C

To assist readers in evaluating the results of human studies of integrative, alternative, and complementary therapies for cancer, the strength of the evidence (i.e., the levels of evidence) associated with each type of treatment is provided whenever possible. To qualify for a level of evidence analysis, a study must:

Separate levels of evidence scores are assigned to qualifying human studies on the basis of statistical strength of the study design and scientific strength of the treatment outcomes (i.e., endpoints) measured. The resulting two scores are then combined to produce an overall score. For an explanation of the scores and additional information about levels of evidence analysis for cancer, see Levels of Evidence for Human Studies of Integrative, Alternative, and Complementary Therapies.

Latest Updates to This Summary (04/05/2024)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

General Information

Revised text to state that in the United States, dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as a separate category from foods, cosmetics, and drugs. Unlike drugs, dietary supplements do not require premarket evaluation and approval by the FDA unless specific disease prevention or treatment claims are made. Also added text to state that the quality and amount of ingredients in dietary supplements are also regulated by the FDA through Good Manufacturing Practices (GMPs). The FDA GMPs requires that every finished batch of dietary supplement meets each product specification for identity, purity, strength, composition, and limits on contamination that may adulterate dietary supplements.

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About This PDQ Summary

Purpose of This Summary

This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of intravenous vitamin C in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians in the care of their patients. It does not provide formal guidelines or recommendations for making health care decisions.

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PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board. PDQ Intravenous Vitamin C. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/about-cancer/treatment/cam/hp/vitamin-c-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389504]

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