Dear pharmacist. Should I take aspirin before my long-haul flight?

There is insufficient evidence to support the use of aspirin for prevention of deep-vein thrombosis (DVT) during long-haul flights. The one published study of aspirin for DVT prophylaxis in high-risk patients on a long-haul flight reported that a single dose of low molecular weight heparin (LMWH) was effective in decreasing DVT risk, whereas aspirin had limited efficacy but exposed some people to gastrointestinal side effects.

The current evidence base is mainly limited to grade 4 recommendations (expert opinion) which has informed the guidance from the Scottish Intercollegiate Guidelines Network and the British Thoracic Society that aspirin may be of some benefit in high risk patients.

However, more recent recommendations from several bodies including the World Health Organization, the British Medical Association and the American College of Chest Physicians advise against the use of aspirin (or any increase in dose for those already taking aspirin) for the prevention of venous thrombosis during flights because of a lack of evidence and the potential risk of adverse effects.

The use of non-pharmacological interventions — such as simple exercises, adequate hydration and compression stockings — is recommended generally, and the use of LMWH has been suggested for high-risk patients.