Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Ann Intern Med. 2004 Apr 6;140(7):533-7.

Vitamin C pharmacokinetics: implications for oral and intravenous use.

Author information

  • 1National Institute of Diabetes and Digestive and Kidney Diseases, the National Cancer Institut, and the Clinical Center, National Institutes of Health, Bethesda, Maryland 20892-1372, USA.

Abstract

BACKGROUND:

Vitamin C at high concentrations is toxic to cancer cells in vitro. Early clinical studies of vitamin C in patients with terminal cancer suggested clinical benefit, but 2 double-blind, placebo-controlled trials showed none. However, these studies used different routes of administration.

OBJECTIVE:

To determine whether plasma vitamin C concentrations vary substantially with the route of administration.

DESIGN:

Dose concentration studies and pharmacokinetic modeling.

SETTING:

Academic medical center.

PARTICIPANTS:

17 healthy hospitalized volunteers.

MEASUREMENTS:

Vitamin C plasma and urine concentrations were measured after administration of oral and intravenous doses at a dose range of 0.015 to 1.25 g, and plasma concentrations were calculated for a dose range of 1 to 100 g.

RESULTS:

Peak plasma vitamin C concentrations were higher after administration of intravenous doses than after administration of oral doses (P < 0.001), and the difference increased according to dose. Vitamin C at a dose of 1.25 g administered orally produced mean (+/-sd) peak plasma concentrations of 134.8 +/- 20.6 micromol/L compared with 885 +/- 201.2 micromol/L for intravenous administration. For the maximum tolerated oral dose of 3 g every 4 hours, pharmacokinetic modeling predicted peak plasma vitamin C concentrations of 220 micromol/L and 13 400 micromol/L for a 50-g intravenous dose. Peak predicted urine concentrations of vitamin C from intravenous administration were 140-fold higher than those from maximum oral doses.

LIMITATIONS:

Patient data are not available to confirm pharmacokinetic modeling at high doses and in patients with cancer.

CONCLUSIONS:

Oral vitamin C produces plasma concentrations that are tightly controlled. Only intravenous administration of vitamin C produces high plasma and urine concentrations that might have antitumor activity. Because efficacy of vitamin C treatment cannot be judged from clinical trials that use only oral dosing, the role of vitamin C in cancer treatment should be reevaluated.

Comment in

PMID:
15068981
[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for Silverchair Information Systems
    Loading ...
    Write to the Help Desk