Clopidogrel-herb Interactions: A Pharmacokinetic and Pharmacodynamic Assessment in a Rat Model.

BACKGROUND: Herbs usually contain a mixture of biologically active constituents, which can interact with numerous prescribed drugs and alter their safety profiles. OBJECTIVES: The current investigation was aimed to evaluate the effect of commonly used herbal products including black seed (Nigella sativa), garden cress (Lepidium sativum), and fenugreek (Trigonella foenum-graecum) on the pharmacokinetics and pharmacodynamics of clopidogrel using a Wistar rat model. METHODS: A GC-MS analysis revealed the presence of several phytoconstitutents (polyphenols) in the extracts of black seed, garden cress, and fenugreek. These polyphenols have the potential to interfere with clopidogrel effect. Plasma concentrations of clopidogrel were measured at different time points in the absence and presence of the concurrent use of tested herbal products and the pharmacokinetic parameters were calculated. Bleeding time was measured in various groups as a measure of the antiplatelet effect of clopidogrel. RESULTS: Area under the plasma concentration-time curves (AUC0-∞) of clopidogrel were 35.53 ±0.89 µg/ml*h (p<0.05), 26.01 ±0.90 µg/ml*h (p>0.05) and 32.80 ±2.51 µg/ml*h (p<0.05) in the black seed, garden cress and fenugreek group, respectively, compared with that of the control group (27.02 ±0.42 µg/ml*h). Treatment with black seed also caused an increase in clopidogrel Cmax by 31.52% (p<0.05) and with fenugreek by 21.42% (p<0.05); Cmax, did not changed with garden cress treatment (6.48 ±0.15 µg/ml versus 6.12 ±0.21 µg/ml, p>0.05). The pharmacodynamic evaluation of the antiplatelet effect of clopidogrel in the presence of herbal products treatment showed a significant prolongation in the bleeding time from a control baseline by ~22-26%, and by added ~8-12% in reference to clopidogrel therapeutic effect (p<0.05). CONCLUSION: The concurrent use of black seed, fenugreek, or garden cress can alter the pharmacokinetics and pharmacodynamics of clopidogrel to varying degrees due to the presence of various bioactive polyphenols. This is probably due to changes in drug disposition and its antiplatelet action. Further confirmation can determine the clinical relevance of these observations and identify the exact constituents responsible for such activities.

Comparative pharmacodynamic effects of two clopidogrel formulations under steady-state conditions in healthy Thai volunteers
.

OBJECTIVE: Clopidogrel is a commonly used antiplatelet aggregation agent. Compared with the reference clopidogrel product, most commercially available generic clopidogrel products contain different crystalline forms of clopidogrel. This study was aimed to compare the pharmacodynamics of a commonly used generic clopidogrel product in Thailand with the reference clopidogrel product under steady state conditions. METHODS: A multiple-dose, randomized 2-way crossover study was conducted in 32 healthy male Thai volunteers. The subjects were assigned to receive 75 mg once daily of the test or the reference product for 7 days with a 2-week wash out period. Blood samples were collected on days 1, 5, 6, and 7 prior to drug administration and at 1, 2, 3, 4, 8, 12, and 24 hours after the last dose administered. The antiplatelet aggregation effects of clopidogrel were determined by using two different ex-vivo platelet aggregation tests including the whole blood impedance assay (WBA) and the VerifyNow® P2Y12 assay. Both pharmacodynamic parameters, the maximal antiplatelet effect (Emax) and the areas under the antiplatelet effect-time curve (AUEC0-24h), were calculated. RESULTS: Neither the mean values of Emax (90.70 ± 15.15 vs. 89.50 ± 10.71% inhibition) nor of AUEC0-24h (1,892.84 ± 657.22 vs. 1,853.58 ± 673.95% inhibition × h) under steady-state conditions obtained using the WBA method of these two clopidogrel products were significantly different. The results obtained using the VerifyNow® P2Y12 assay were consistent with those of the WBA assay. CONCLUSION: This study clearly demonstrated that ex-vivo antiplatelet aggregation effect under steady-state conditions of the test product was not significantly different from the reference product.
.

Prasugrel.

Prasugrel is a third-generation thienopyridine which selectively inhibits the platelet P2Y(12) receptor more rapidly, more potently, and with less interindividual response variability compared with the second-generation thienopyridine clopidogrel. Large-scale phase III clinical testing showed that in high-to moderate-risk acute coronary syndrome patients undergoing percutaneous coronary intervention, prasugrel translates into a greater reduction in ischemic events, including stent thrombosis, in the short and long term compared to clopidogrel. Prasugrel, however, is associated with an increased risk of major bleeding, which is more pronounced in certain patient subgroups. The ideal patient population for prasugrel use are those patients without prior transient ischemic attack/stroke, <75 years of age and >60 kg in whom the greatest ischemic benefit is achieved without a significant increase in major bleeding risk. Dose modifications in specific populations or at given time-points may represent an avenue to minimize bleeding risk and therefore maximize the clinical benefit of prasugrel. Ongoing clinical studies with prasugrel will better define the safety and efficacy profiles of this agent and potentially set the basis for new indications for use.