Acetylsalicylic acid × Naproxen

Aspirin and naproxen are both NSAIDs: together they damage the stomach lining more and cause ulcers and bleeding more often (aspirin 100 mg and naproxen SmPCs). Naproxen taken for more than one day in a row also blunts the antiplatelet effect of low-dose aspirin, and this can last several days after naproxen is stopped; the Spanish SmPC calls its clinical relevance unknown (naproxen SmPC). In a study cited in the US naproxen label (FDA), the interaction was stronger when naproxen was taken 30 minutes before aspirin and most marked in the first days after naproxen was stopped.

Black tarry stools, vomiting blood, abdominal pain, weakness, dizziness and cold sweat are signs of gastrointestinal bleeding. Bruising, bleeding gums and nosebleeds are less common. The weaker antiplatelet effect of aspirin causes no symptoms by itself, but in patients with high cardiovascular risk it can reduce the cardiovascular protection aspirin gives.

The naproxen SmPC contraindicates naproxen with other NSAIDs and asks for special caution with low-dose aspirin (naproxen SmPC). Avoid NSAIDs with aspirin whenever possible (aspirin 100 mg SmPC). The FDA does not generally recommend naproxen with analgesic doses of aspirin because of bleeding risk. For patients on low-dose aspirin for cardioprotection who need occasional pain relief, the FDA advises an NSAID that does not interfere with aspirin or a non-NSAID analgesic; naproxen is not a substitute for low-dose aspirin (US naproxen label). If naproxen is still needed with low-dose aspirin, consider gastroprotection with misoprostol or a proton pump inhibitor (naproxen SmPC) and watch for signs of bleeding (US naproxen label).