Intake ofStJohn's wort improves the glucose tolerance in healthy subjects who ingest metformin compared with metformin alone

• DOI: 10.1111/bcp.12510
• Publication Date: 2014-09-16T04:46:57Z
• Authors: Tore Bjerregaard ...; Rasmus Steen Pede...; Per Damkier; Mette Marie Houga...; Søren Feddersen; John Teilmann Larsen; Kurt Højlund; Kim Brøsen
• Keywords: Adult; Blood Glucose; Male; 0301 basic medicine; 0303 health sciences; Cross-Over Studies; Plant Extracts; Glucose Tolerance Test; Antidepressive Agents; Metformin; 3. Good health; Young Adult; 03 medical and health sciences; Insulin Secretion; Humans; Hypoglycemic Agents; Insulin; Drug Interactions; Hypericum

AimsOur objective was to investigate the steady‐state pharmacokinetic and pharmacodynamic interaction between the antidepressive herbal medicineStJohn's wort and the antidiabetic drug metformin.MethodsWe performed an open cross‐over study in 20 healthy male subjects, who received 1 g of metformin twice daily for 1 week with and without 21 days of preceding and concomitant treatment withStJohn's wort. The pharmacokinetics of metformin was determined, and a 2 h oral glucose tolerance test was performed.ResultsStJohn's wort decreased the renal clearance of metformin but did not affect any other metformin pharmacokinetic parameter. The addition ofStJohn's wort decreased the area under the glucose concentration–time curve [702 (95% confidence interval, 643–761)vs. 629 min*mmol/L (95% confidence interval, 568–690),P= 0.003], and this effect was caused by a statistically significant increase in the acute insulin response.ConclusionsStJohn's wort improves glucose tolerance by enhancing insulin secretion independently of insulin sensitivity in healthy male subjects taking metformin.