Vitamin C pharmacokinetics of plain and slow release formulations in smokers

Background & aims: Combination of the antioxidants ascorbic acid in slow release formulation and α-tocopherol can retard the progression of atherosclerosis. In order to determine if differences in formulation could explain some of the different results in the intervention trials we determined selected pharmacokinetics for two different formulations of ascorbic acid together with α-tocopherol. Methods: Single-blinded, randomised, placebo-controlled intervention study with 48 healthy men, aged 20–65 years, smoking ⩾5 cigarettes/day. Subjects received 250mg plain release ascorbic acid and 91mg plain release d-α-tocopheryl acetate, 250mg slow release ascorbic acid and 91mg plain release d-α-tocopheryl acetate or placebo twice daily for 4 weeks. A series of blood samples were collected after administration of the first dose and repeated after 4 weeks of supplementation. Results: The fluctuation of ascorbic acid plasma concentrations decreased significantly (P=0.003) after 4 weeks supplementation in the slow versus the plain release group. Conclusions: This study shows that there were pharmacokinetic differences between plain and slow release formulations of ascorbic acid. However, these effects are small and unlikely to be of significant clinical importance.