Positive Health Online

Abstract

MUELLER and colleagues, Center of Pharmacology and Toxicology, Institute of Clinical Pharmacology, University of Rostock, Rostock, Germany, silke.mueller@med.uni-rostock.de, have investigated the effect of the dose and preparation of St John's wort on the pharmacokinetics of digoxin.

Background

St John's wort preparations vary in composition, main constituents, formulation, and recommended daily dosages. The aim of this study was to investigate pharmacokinetic interactions between different commercially available preparations of St John's wort with digoxin, a commonly used heart medication.

Methodology

In this randomized, placebo-controlled parallel-group study, 96 healthy volunteers were enrolled. In a first phase, they were 'loaded' with digoxin, then co-medicated for 14 days with placebo or one of 10 St John's wort preparations varying in dose and formulation. The pharmacokinetics of digoxin were determined before co-medication and on the last day of co-medication.

Results

Placebo or hyperforin-free extract had no interactions with digoxin. Co-medication with a hyperforin-rich extract resulted in a reduction of available digoxin by about 25%, as did co-medication with higher doses of preparations less rich in hyperforin.

Conclusion

The interactions of St John's wort with digoxin appear to be dependent on preparations and dosage and particularly with hyperforin content.

References

Mueller SC, Uehleke B, Woehling H, Petzsch M, Majcher-Peszynska J, Hehl EM, Sievers H, Frank B, Riethling AK, Dreweloe B. Effect of St John's wort dose and preparations on the pharmacokinetics of digoxin. Clinical Pharmacology and Therapeutics 75 (6): 546-557, Jun 2004.