Hypericum pharmacodynamics

Schellenberg R, Sauer S, Dimpfel W. (1998). Pharmacodynamic effects of two different hypericum extracts in healthy volunteers measured by quantitative EEG. Pharmacopsychiatry. 31(suppl 1) 44-53. 

Timoshanko, A., Stongh, C., Vitetta, L., Nathan, P.J. A preliminary investigation on the acute pharmacodynamic effects of hypericum on cognitive and psychomotor performance. Behav. Pharmacol. 12, 635-640, 2001. 

Although little is known about the pharmacodynamics of hypericum, even less is known about its metabolism or its potential to affect the metabolism of other drugs. However, hypericum has recently been shown to produce substantial induction of CYP 3A3/4 such that a warning has been issued about its ability to decrease the levels of protease inhibitors to less than effective concentrations. Thus, physicians will likely need to prescribe higher doses of CYP 3A3/4 substrates when a patient is taking hypericum just as in patients on carbamazepine, a classic CYP 3A 3/4 inducer. 

Schmidt and coworkers [269] tested the pharmacodynamic interaction of Hypericum and alcohol. They included 32 healthy young volunteers of both sexes in a cross-over trial. In a randomized sequence, the subjects received 3 x 300 mg/day of the Hypericum extract LI 160 for 7 days and placebo for another 7 days. On day 7 and day 14 they underwent different tests of reaction time and psychomotor function after oral intake of individually calculated amounts of alcohol resulting in blood concentrations between 45 and 80 ml/1. 

In conclusion, a relevant pharmacodynamic interaction of Hypericum extract and alcohol, particularly an enhancement of the adverse effects of alcohol, could be ruled out by comprehensive testing procedures. 

The CSM in the UK noted that pharmacodynamic (potentiation) interactions have been identified between triptans and St John s wort Hypericum perforatum) leading to an increased risk of adverse effects. They surest that patients taking triptans should not take St John s wort preparations. ... 

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