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(R)) 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-infinity) 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.