Dose reduction, oral application, and order of intake to preserve aspirin antiplatelet effects in dipyrone co-medicated chronic artery disease patients.

BACKGROUND: Dipyrone comedication in aspirin-treated patients is associated with impaired pharmacodynamic response to aspirin (high on-treatment platelet reactivity [HTPR]). Additionally, in small observational studies, an association with impaired outcome has been described. In this uncontrolled, hypothesis-generating study, we aimed to investigate strategies to prevent this drug-drug interaction in patients with coronary artery disease (CAD). METHODS: We analyzed pharmacodynamic response to aspirin in 80 dipyrone co-medicated CAD patients. Aspirin antiplatelet effects were measured using arachidonic acid (AA)-induced light-transmission aggregometry (LTA). Platelet reactivity was associated with daily dose, administration form, and frequency. Additionally, we conducted a time-series analysis in patients with HTPR to aspirin with re-evaluation of pharmacodynamic response to aspirin after 5 days. RESULTS: Patients' mean age was 75.5 ± 9.8 years. Forty-three (54%) were male, 22 (27.5%) obese, and 38 (47.5%) diabetics. Baseline characteristics, cardiovascular risk factors, comorbidities, comedication, or laboratory parameters did not differ between patients with or without HTPR. HTPR to aspirin occurred in 34 out of 80 patients (42.5%). The incidence of HTPR was associated with dipyrone daily dose (< 1 g/day: HTPR 20% vs. > 3 g/day: HTPR 50%, p > 0.0001) and form of administration (i.v. 87.5% vs. oral 37.5%; p < 0.0001). A strict order of intake (aspirin 30 min prior to dipyrone) restored aspirin antiplatelet effects in all patients (HTPR before 100% vs. HTPR after 0%, p = 0.0002). CONCLUSION: This study shows that dipyrone should be used with caution in aspirin-treated patients. If dipyrone seems indispensable, the lowest effective dose and a strict order of intake seem favorable.