Naproxen is even more dangerous to dogs than ibuprofen due to a very long half-life.
Brand names include Aleve, Naprosyn and Anaprox; all are toxic.
Naproxen is an NSAID that inhibits both COX-1 and COX-2, reducing protective prostaglandins. Dogs have an exceptionally long elimination half-life for naproxen (~74 hours), meaning even small repeated doses build to toxic concentrations. Gastric perforation and acute kidney injury can result from a single tablet.
Sources
Toxicity begins around 5 mg/kg. A single 220 mg Aleve tablet can cause severe injury in a 10 kg dog.
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