PT - JOURNAL ARTICLE AU - Padayatty, Sebastian J. AU - Riordan, Hugh D. AU - Hewitt, Stephen M. AU - Katz, Arie AU - Hoffer, L. John AU - Levine, Mark TI - Intravenously administered vitamin C as cancer therapy: three cases AID - 10.1503/cmaj.050346 DP - 2006 Mar 28 TA - Canadian Medical Association Journal PG - 937--942 VI - 174 IP - 7 4099 - http://www.cmaj.ca/content/174/7/937.short 4100 - http://www.cmaj.ca/content/174/7/937.full SO - CMAJ2006 Mar 28; 174 AB - Early clinical studies showed that high-dose vitamin C, given by intravenous and oral routes, may improve symptoms and prolong life in patients with terminal cancer. Double-blind placebo-controlled studies of oral vitamin C therapy showed no benefit. Recent evidence shows that oral administration of the maximum tolerated dose of vitamin C (18 g/d) produces peak plasma concentrations of only 220 μmol/L, whereas intravenous administration of the same dose produces plasma concentrations about 25-fold higher. Larger doses (50–100 g) given intravenously may result in plasma concentrations of about 14 000 μmol/L. At concentrations above 1000 μmol/L, vitamin C is toxic to some cancer cells but not to normal cells in vitro. We found 3 well-documented cases of advanced cancers, confirmed by histopathologic review, where patients had unexpectedly long survival times after receiving high-dose intravenous vitamin C therapy. We examined clinical details of each case in accordance with National Cancer Institute (NCI) Best Case Series guidelines. Tumour pathology was verified by pathologists at the NCI who were unaware of diagnosis or treatment. In light of recent clinical pharmacokinetic findings and in vitro evidence of anti-tumour mechanisms, these case reports indicate that the role of high-dose intravenous vitamin C therapy in cancer treatment should be reassessed.