The ability of vitamin C to exert a toxic effect on tumor cells in vitro at high concentrations (more than 1000 μmol / L) opens up prospects for its use in the treatment of cancer patients. Clinical trials of the use of vitamin C in patients with terminal oncological pathology have shown the clinical effect of the treatment, however, two subsequent double-blind placebo-controlled studies have not confirmed the results. previously optimistic. However, in these studies, different routes of administration of vitamin C were used. It should be borne in mind that the concentration of vitamin C in the blood plasma can vary considerably depending on the route of administration.

The purpose of the study by S.J. Padayatty et al. (USA), was the identification of the dependence of the concentration of vitamin C in the blood plasma on the route of administration (inside vs intravenously). The study involved 17 healthy volunteers.

According to the data obtained, the maximum concentrations of vitamin C in the blood plasma were higher with intravenous administration of the drug compared to oral administration (p less than 0.001), and the differences increased with increasing dose.. When taking vitamin C at a dose of 1.25 g orally, the maximum average concentration reached 134.8 ± 20.6 μmol / L per compared to 885 ± 201.2. μmol / L when administered intravenously. For the maximum tolerated oral dose (3 g every 4 hours), the maximum plasma concentration of vitamin C, determined by pharmacokinetic modeling, was 220 μmol / L compared to 13400 μmol / l with intravenous administration of the drug at a dose of 50 g. The maximum expected concentrations of vitamin C in the urine when administered intravenously were 140 times higher than when the maximum dose of the drug was administered orally.

Thus, the concentration of vitamin C in the blood plasma when taken orally is relatively low. Only intravenous administration allows you to create high concentrations of vitamin C in blood serum and urine, possibly with anti-tumor activity. Since data from studies evaluating the efficacy of vitamin C in cancer patients who have used the oral route cannot be considered as correct, the role of vitamin C in the treatment of cancer should be reviewed.