Progress in platelet medicine: focus on stent thrombosis and drug resistance

Concomitant use of drugs known to cause interactions with oral antiplatelets-polypharmacy in acute coronary syndrome outpatients in Finland

PURPOSE

Use of oral antiplatelets (OAPs) is essential for preventing thrombotic events in patients with acute coronary syndrome (ACS). Effects of clopidogrel, prasugrel, and ticagrelor may be enhanced due to pharmacodynamic interactions, but as CYP substrates, they are prone to pharmacokinetic interactions too. The aim was to study polypharmacy in ACS patients following hospital discharge.

METHODS

This observational drug utilization study linked patient-level data from nationwide registers. The study population consisted of adult ACS patients discharged from Finnish hospitals in 2009-2013. Logistic regression was used to model the probability of drug-drug interactions with odd ratios for predefined predictors such as age, gender, and ACS type.

RESULTS

In the cohort of 54,416 ACS patients, 91% of those treated with OAP received clopidogrel. Of clopidogrel-treated patients, 12% purchased warfarin at least once while on clopidogrel treatment. Old age, male sex, ST-elevation myocardial infarction as index event, and a history of previous ACS events were associated with an increased risk of warfarin-OAP interaction (p < 0.001 for all). Ibuprofen, and serotonergic drugs tramadol, citalopram, and escitalopram were the next most common drugs causing pharmacodynamic interactions. In general, concomitant use of drugs known to cause pharmacokinetic interactions was rare, but both esomeprazole and omeprazole were prescribed in more than 6% of clopidogrel-treated patients.

CONCLUSIONS

Warfarin and ibuprofen were the most commonly used concomitant medications causing pharmacodynamic interactions and potentially increasing the risk of bleeding in OAP-treated patients. Esomeprazole and omeprazole were used in clopidogrel-treated patients although there are alternatives available for gastric protection.

Aspirin, clopidogrel, and the surgeon

The rising use of antiplatelet therapy for primary prevention and secondary prevention of cardiovascular and cerebrovascular events poses a dilemma for physicians in the perioperative period. The proven benefits of aspirin in preventing further thrombotic events in patients with prior ACS or stroke make it difficult to withdraw this therapy. The risk of hypercoagulability associated with surgery is also independent of antiplatelet withdrawal, but adds to the rebound effect of platelet responsiveness. Therefore, aspirin should be continued whenever feasible. Similarly, the use of thienopyridines such as clopidogrel, especially for the prevention of stent thrombosis, should be maintained for at least the recommended time frame, if not longer. It is recognized that maintaining antiplatelet therapy is also not without risk, as bleeding complications have been well documented. Unfortunately, current perioperative guidelines do not often provide a simple solution for management. Therefore, the risk of bleeding has to be weighed against the risk of thrombosis, and decisions should be made with all providers caring for the patient on an individual basis.

Progress in platelet blockers: the target is the P2Y12 receptor

The considerable progress in P2Y12-platelet blockers has important perioperative implications due to a family of novel agents beyond clopidogrel. Although prasugrel is more potent than clopidogrel due to more efficient hepatic metabolism, it is limited clinically by its irreversibility and bleeding risks. Ticagrelor, as the first approved direct and reversible oral P2Y12 blocker, still is limited clinically by its novel side-effect profile. Intravenous reversible P2Y12 blockade is possible now with both cangrelor and elinogrel, although both agents are still in clinical development. Furthermore, elinogrel offers the possibility of both oral and parenteral P2Y12 blockade with a single agent. Future trials likely will continue to evaluate and compare the safety and efficacy of these agents in multiple clinical settings, including the perioperative period.