How long does naproxen stay in your system?

After taking your last dose of naproxen it should be out of your system within 93.5 hours.
Naproxen has an elimination half life of 12 to 17 hours. This is the time it takes for your body to reduce plasma drug levels by half. It takes approximately 5.5 x elimination half-life for a drug to be eliminated from your system.
Therefore naproxen will be in your system for about 93.5 hours (5.5 x 17 hours).

For more information see:

https://www.drugs.com/pro/naprosyn.html