Effect of gender difference on platelet reactivity.

BACKGROUND: Previous studies have suggested that women do not accrue equal therapeutic benefit from antiplatelet medication as compared with men. The physiological mechanism and clinical implications behind this gender disparity have yet to be established. METHODS: On-treatment platelet reactivity was determined in 717 men and 234 women on dual antiplatelet therapy, undergoing elective coronary stent implantation. Platelet function testing was performed using arachidonic acid and adenosine diphosphate-induced light transmittance aggregometry (LTA) and the VerifyNow P2Y12 and Aspirin assays. Also the incidence of all-cause death, non-fatal acute myocardial infarction, stent thrombosis and ischaemic stroke was evaluated. RESULTS: Women had higher baseline platelet counts than men. Women exhibited a higher magnitude of on-aspirin platelet reactivity using LTA, but not using the VerifyNow Aspirin assay. The magnitude of on-clopidogrel platelet reactivity was significantly higher in women as compared with men with both tests used. The cut-off value to identify patients at risk as well as the incidence of clinical endpoints was similar between women and men (16/234[6.8%] vs. 62/717[8.6%], p = 0.38). CONCLUSION: Although the magnitude of platelet reactivity was higher in women, the absolute difference between genders was small and both the cut-off value to identify patients at risk and the incidence of the composite endpoint were similar between genders. Thus, it is unlikely that the difference in platelet reactivity accounts for a worse prognosis in women.

Combined influence of proton-pump inhibitors, calcium-channel blockers and CYP2C19*2 on on-treatment platelet reactivity and on the occurrence of atherothrombotic events after percutaneous coronary intervention.

BACKGROUND: The carriage of CYP2C19*2 and the use of proton-pump inhibitors (PPIs) and calcium-channel blockers (CCBs) has been associated with the diminished efficacy of clopidogrel. However, previous studies have only assessed the isolated impact of these risk factors for clopidogrel poor response. OBJECTIVES: The aim of the present study was to investigate the impact of the combined presence of three risk factors for clopidogrel poor response, that is, the use of CCBs, PPIs and the carriage of CYP2C19*2, on on-treatment platelet reactivity and the occurrence of atherothrombotic events in 725 patients on dual antiplatelet therapy undergoing elective coronary stenting. METHODS: In a prospective, follow-up study, on-treatment platelet reactivity was quantified using ADP-induced light transmittance aggregometry (LTA) and the VerifyNow P2Y12 assay. The clinical study endpoint was the composite of all-cause mortality, myocardial infarction, stent thrombosis and stroke at 1 year after stenting. RESULTS: Patients with either one or more than one risk factor exhibited increased platelet reactivity (mean relative increase one risk factor: 11% and > 1 risk factor: 22%, respectively). Sixty-four events occurred during follow-up (8.8% of the study population). Patients with one risk factor for clopidogrel poor response did not have an increased risk of the composite endpoint. However, patients using both CCBs and PPIs and carriers of CYP2C19*2 who used CCBs had a statistically significant increased risk of the composite endpoint [hazard ratio(HR)(adj) 2.2 95% CI, 1.0-5.3, P = 0.044 and HR(adj) 3.3 95% CI, 1.1-9.8, P = 0.032, respectively]. CONCLUSIONS: The presence of more than one of the three investigated risk factors for clopidogrel poor response is associated with an increased risk of adverse cardiovascular events within 1 year after elective coronary stenting.

The use of the VerifyNow system to monitor antiplatelet therapy: a review of the current evidence.

Multiple studies have demonstrated the effectiveness of dual or triple antiplatelet therapy with aspirin, clopidogrel and glycoprotein (GP) IIb/IIIa therapy in patients with acute coronary syndromes as well as in patients undergoing coronary stent implantation. In the last few years, it is becoming clear that not all patients receive the full benefits with the current standard dosages of antiplatelet therapy. Specifically, numerous studies have revealed a wide interindividual variability in the response to these antiplatelet agents and, more importantly, both nonresponsiveness as well as a heightened residual platelet reactivity have been linked to the occurrence of adverse cardiovascular events. Therefore, assays that identify those patients with an impaired responsiveness or a heightened platelet reactivity despite dual antiplatelet therapy may contribute to better risk stratification and will probably improve clinical outcome when appropriate action is initiated. Likewise, a considerable number of patients do not achieve the minimal inhibition of aggregation threshold with the current recommended weight-adjusted dosages of GP IIb/IIIa therapy. Identifying and optimizing the absolute degree of platelet inhibition in this subgroup of patients will probably improve clinical outcome. The VerifyNow platform is one of the most user friendly point-of-care platelet function test systems because it produces rapid results at the patient bedside. The purpose of the present paper is to give insight into the principal mechanisms of the VerifyNow system, to discuss its clinical utility for the monitoring of antiplatelet therapy and to discuss the proposed cut-off levels to segregate responders from non-responders for the different types of antiplatelet therapy.

[Prolonged diminished effect of coumarin derivatives after use of rifampicin]. / Langdurig verminderd effect van cumarinederivaten na gebruik van rifampicine.

A 73-year-old woman with endocarditis was treated with flucloxacillin and rifampicin. She already used the anticoagulant acenocoumarol because of a recent heart valve replacement. After starting rifampicin therapy the sensitivity for the acenocoumarol was reduced. The international normalised ratio (INR) did not exceed 2.0, while values of 2.5-3.5 were required. Increase of the daily dose of acenocoumarol with a factor 6 compared to the dose which resulted in a therapeutic INR before hospitalisation, proved insufficient to obtain a therapeutic INR during long-term rifampicin therapy. 21 days after rifampicin discontinuation the INR finally responded to high coumarin dosages. The breakdown of coumarins in the liver is increased by rifampicin due to induction of several isoenzymes of the cytochrome P450-system. This case illustrates that sensitivity to coumarins can be decreased profoundly even after discontinuation of rifampicin therapy. INR should be monitored closely not only at the start and discontinuation of rifampicin therapy, but also during the weeks after discontinuation of rifampicin treatment.

Review of global regulations concerning biowaivers for immediate release solid oral dosage forms.

The regulations with respect to biowaivers for immediate release (IR) solid oral dosage forms in the USA, the EU, Japan and from the World Health Organization (WHO) are summarized and compared. Two case studies are presented, one from our own files and one from the open literature, showing the similarities and the differences among the qualification requirements of the four systems. The regulatory experience gained up to now is reviewed and expected future trends are discussed.