Reporting on Adverse Clinical Events

The effect of St John’s Wort on glucose tolerance (assessed by an oral glucose tolerance test) was evaluated in 10 healthy men (median age = 26 years) with normal blood glucose. The study consisted of 3 different phases: (a) baseline prior to St John’s Wort; (b) after 21 days treatment with St John’s Wort; and (c) at least 6 weeks after St John’s Wort was stopped. The subjects fasted for 12 hours and ingested 75 g glucose in 250 mL of water. Blood samples were drawn at 0, 15, 30, 45, 60, 90, and 120 minutes and analyzed for plasma glucose, serum insulin, and C-peptide concentrations. There was a median of 48 days (range = 22-78) between phases A and B and a median of 48 days (range = 38-94) between phases B and C. The fasting levels of plasma glucose, serum insulin, and C-peptide did not differ between the 3 phases. The total glucose area under the curve was increased (18%) during St John’s Wort treatment with St John’s Wort and by an additional 17% at least 6 weeks after therapy was stopped. The incremental glucose area under the curve increased by 48% and 31% for the same time periods, respectively. The 2-hour glucose increased by approximately 40% from baseline to phases B and C. No changes in insulin clearance occurred. The authors concluded that, in this preliminary study, St John’s Wort impairs glucose tolerance in healthy subjects, most likely mediated by decreased insulin secretion. They also suggested that further studies are required to confirm these results. St John’s Wort [St John’s Wort] Stage TB et al (TB Stage, Clinical Pharmacology, Department of Public Health, University of Southern Denmark, JB Winsloews Vej 19, 2, DK-5000 Odense C, Denmark; e-mail: tstage@health.sdu.dk) Impaired glucose tolerance in healthy men treated with St. John’s Wort. Basic Clin Pharmacol Toxicol 118:219–224 (Mar) 2016