Modification of propranolol's bioavailability by Eurycoma longifolia water-based extract.

WHAT IS KNOWN AND BACKGROUND

Eurycoma longifolia (E. longifolia), a herb commonly consumed for its aphrodisiac properties, is widely used by Asian males. This may include hypertensive patients receiving propranolol which may cause sexual dysfunction as one of its side-effects. There is no published study of the potential pharmacokinetic interaction between propranolol and the herb.

OBJECTIVE

To study propranolol's pharmacokinetics when E. longifolia is consumed, comparing volunteers given either propranolol or a placebo.

METHODS

This is a placebo-controlled randomized single-blinded crossover study of the effect of a water-based extract of E. longifolia on the pharmacokinetics of a single dose of proporanolol (Inderal(®)) in 14 healthy non-smoker young males. Eighty milligram of propranonol was orally administered with (i) placebo (Lactose) or (ii) 200 mg of water-based extract of E. longifolia (0·0272 ± 0·0026%eurycomanone) following an overnight fasting. Blood samples were collected at 0, 0·5, 1, 1·5, 2, 3, 4, 6, 8 and 10 h for propranolol's plasma concentration determinations using a validated high-performance liquid chromatography (HPLC) method.

RESULTS AND DISCUSSION

When propranolol was administered with E. longifolia, its bioavailability (AUC0-∞) decreased by 29% while C(max) was reduced by 42% and T(max) was significantly prolonged by almost 86%. The terminal elimination half-life, however, was not significantly affected.

CONCLUSION

The bioavailability of propranolol is significantly decreased when consumed together with E. longifolia. The interaction is due to a reduction in absorption, rather than an increase in propranolol's metabolism. Although the pharmacodynamics of propranolol was not affected in healthy volunteers, caution is still advisable with co-administration of the drug and the herb.