Many travellers take aspirin before a long haul flight as an important part of their strategy to lower the risk of deep vein thrombosis (DVT). However, recent research shows that this useful strategy may be completely blocked if the traveller is taking medicines containing ibuprofen.
Ibuprofen is frequently taken for relief of arthritic pain, muscular pain, or headaches, but just one tablet is sufficient to completely block the platelet inhibition effect of aspirin - that is its clot prevention action. This would leave long haul travellers unaware that they are at greater risk of DVT.
Many branded pain relievers contain ibuprofen, and travellers should check the packaging of their pain relievers before use when flying.
Paracetamol does not interfere with aspirin in this way and can be taken to treat headache and other pain or fever during travelling without in any way compromising travellers' precautions against DVT.
Reference:New England Journal of Medicine; Dec 20, 2001; 345(25); 1809-17.