The present investigation evaluated the effects of aprotinin, an inhibitor of kallikrein, on blood pressure responses, heart rate, and duration of hypotension induced by acute administration of captopril and enalapril (angiotensin-converting enzyme inhibitors) in anaesthetized spontaneously hypertensive rats. Captopril (20 mg/kg) and enalapril (20 mg/kg) administered intravenously caused a significant (p < 0.001) fall in systolic and diastolic blood pressures in the absence of aprotinin. In contrast, captopril (20 mg/kg) and enalapril (20 mg/kg) failed (p > 0.05) to cause a fall in systolic and diastolic blood pressures in the presence of aprotinin (2 mg/kg). Captopril and enalapril were able to significantly reduce the heart rate (p < 0.05 and p < 0.001) in the presence as well as in the absence of aprotinin. The duration of hypotension produced by captopril and enalapril was abolished significantly (p < 0.001) in the presence of aprotinin. These findings may suggest that captopril and enalapril caused hypotension via the kallikrein pathway, since the kallikrein inhibitor aprotinin can antagonize the hypotensive responses of these agents. Thus, kallikrein may be an independent mediator in the regulation of blood pressure.
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.