Intake of St John's wort improves the glucose tolerance in healthy subjects who ingest metformin compared with metformin alone.
AIMS
Our objective was to investigate the steady-state pharmacokinetic and pharmacodynamic interaction between the antidepressive herbal medicine St John's wort and the antidiabetic drug metformin.


METHODS
We 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 with St John's wort. The pharmacokinetics of metformin was determined, and a 2 h oral glucose tolerance test was performed.


RESULTS
St John's wort decreased the renal clearance of metformin but did not affect any other metformin pharmacokinetic parameter. The addition of St John'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.


CONCLUSIONS
St John's wort improves glucose tolerance by enhancing insulin secretion independently of insulin sensitivity in healthy male subjects taking metformin.
['Stage|Tore Bjerregaard|TB|', 'Pedersen|Rasmus Steen|RS|', 'Damkier|Per|P|', 'Christensen|Mette Marie Hougaard|MM|', 'Feddersen|Søren|S|', 'Larsen|John Teilmann|JT|', 'Højlund|Kurt|K|', 'Brøsen|Kim|K|']
D000328:Adult D000928:Antidepressive Agents D001786:Blood Glucose D018592:Cross-Over Studies D004347:Drug Interactions D005951:Glucose Tolerance Test D006801:Humans D020902:Hypericum D007004:Hypoglycemic Agents D007328:Insulin D000078790:Insulin Secretion D008297:Male D008687:Metformin D010936:Plant Extracts D055815:Young Adult
St John's wort metformin pharmacokinetics pharmacodynamics drug-herb interaction