diclofenac and aspirin

MajorAvoid this combination where possible.

Mechanism

Pharmacodynamic interaction: both diclofenac and aspirin inhibit COX-1, resulting in additive gastrointestinal mucosal damage and bleeding risk. Additionally, diclofenac may competitively inhibit platelet COX-1, potentially reducing the irreversible antiplatelet effect of aspirin when given concurrently.

What it means clinically

Concomitant use increases the risk of gastrointestinal ulceration, bleeding, and perforation. It may also reduce the cardioprotective effect of aspirin, increasing the risk of thrombotic events in patients taking aspirin for cardiovascular prophylaxis.

What to do

Avoid concurrent use if possible. If combination is necessary, use the lowest effective dose of diclofenac for the shortest duration, consider gastroprotective therapy (e.g., PPI), and administer aspirin at least 30 minutes before diclofenac to minimise interference. Monitor for signs of GI bleeding and cardiovascular events.

Evidence

Well established through clinical studies and pharmacodynamic research. Widely recognised in prescribing guidelines and drug interaction databases.

The two drugs

diclofenacnonsteroidal anti-inflammatory drugRead the monograph aspirinNSAID, antiplateletRead the monograph

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Other interactions involving diclofenac or aspirin

Educational reference for students and clinicians in training. It does not replace professional judgement, local protocols or current prescribing information.