Setting: Academic medical center. Participants: 17 healthy hospitalized volunteers.

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 concentra-tions vary substantially with the route of administration. Design: Dose concentration studies and pharmacokinetic model-ing