Effects of garden cress, fenugreek and black seed on the pharmacodynamics of metoprolol: an herb-drug interaction study in rats with hypertension

Abstract

Context Garden cress (GC), fenugreek (FG), and black seed (BS) are traditional herbal medicine for managing hypertension. Objective The effects of the three herbs on the pharmacodynamics of metoprolol tartrate (MT) in hypertensive rats were investigated. Materials and methods Wistar rats were divided in five groups (n = 6). Group I served as normal control group and Group II (hypertensive control group) had rats treated orally with N-nitro L-arginine methyl ester (L-NAME, 40 mg/kg/day) only. Groups III, IV, and V rats were orally treated with L-NAME (40 mg/kg/day) + GC (300 mg/kg, once daily), L-NAME (40 mg/kg/day) + FG (300 mg/kg, once daily) and L-NAME (40 mg/kg/day) + BS (300 mg/kg, once daily), respectively, for 2 weeks, and on the 14th day, blood pressure and heart rate were recorded using a tail-cuff blood pressure-measuring system. On the 16th day, a single dose of MT (10 mg/kg) was orally administered, and the rats’ blood pressure and heart rate were recorded. Results GC, FG, and BS decreased systolic blood pressure (SBP) by 8.7%, 8.5%, and 8.7%, respectively, in hypertensive rats. A greater decrease in SBP by 14.5%, 14.8%, and 16.1% was observed when hypertensive rats were treated with L-NAME + GC + MT, L-NAME + FG + MT, and L-NAME + BS + MT, respectively. Similarly, hypertensive rats treated with the combination of herbs and MT had significantly lower diastolic blood pressure (DBP) than those treated with herbs alone and those treated with L-NAME alone. Conclusions The combination of investigated herbs and MT had a beneficial effect on hypertension. However, the concurrent administration of drugs, particularly those predominantly cleared through CYP450 2D6-catalyzed metabolism, with the three investigated herbs should be considered with caution.