Resistance to anti-platelet agents.

In the last few years, the concept of resistance to antiplatelet agents has been largely emphasized in the medical literature, although its definition is still uncertain. The real prevalence of resistance to aspirin appears to be rather low. In contrast, resistance to clopidogrel (a P2Y12 inhibitor), which is mostly due to inefficient metabolism of the pro-drug clopidogrel to its active metabolite, is a rather frequent condition, which is associated with lower clinical efficacy of the drug. The proposed solution to the problem of clopidogrel resistance, based on monitoring the pharmacological response with platelet function tests, is cumbersome, not effective in all treated patients and not practicable yet, because the most appropriate laboratory test has not yet been identified. The use of new P2Y12 inhibitors, such as prasugrel and ticagrelor, which adequately inhibit P2Y12-dependent platelet function in the vast majority of treated subjects, appears the best solution to the problem of clopidogrel resistance.