Dipyrone comedication in aspirin treated stroke patients impairs outcome.

BACKGROUND: >50% of stroke patients rely on analgesic medication to control pain. Aspirin is the mainstay of medical treatment of stroke patients; however analgesic medication with dipyrone impairs aspirin antiplatelet effects ex-vivo. The clinical impact of this impairment is unknown. Therefore, we aimed to determine aspirin antiplatelet effects and neurological outcome in stroke patients with aspirin and dipyrone comedication.

METHODS: We conducted a prospective cohort study in 41 patients with stroke. Primary outcome was pharmacodynamic response to aspirin in dipyrone treated stroke patients. Secondary outcome was neurological recovery after stroke. Pharmacodynamic response to aspirin was measured using arachidonic acid induced aggregation in light-transmission aggregometry. Neurological outcome was determined three months after stroke onset by telephone interview.

RESULTS: Patient's characteristics were similar in the aspirin-alone group and the aspirin+dipyrone group. Impaired pharmacodynamic response to aspirin occurred in 62% (14/21) of patients with aspirin and dipyrone co-medication. Only 10% (2/20) of aspirin treated patients without analgesic comedication displayed residual platelet reactivity (P=0.001; odds ratio [OR], 18 [95% CI, 3.2-100]). Excellent neurological recovery (measured by three months follow-up modified Rankin Scale<2) was observed in 80% (16/20) of patients in the aspirin-alone group and 48% (10/21) of patients in the aspirin+dipyrone group (P=0.037; OR, 4.4 [95% CI, 1.1-17.7]).

CONCLUSIONS: Dipyrone comedication in patients with stroke impairs pharmacodynamic response to aspirin. This is associated with worse clinical outcome. Therefore dipyrone should be used with caution in aspirin treated stroke patients.

CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/show/NCT02148939; Identifier: NCT02148939.