Naproxen, in most cases, should not cause you to be tired like Flexeril (cyclobenzaprine) does. Flexeril is a muscle relaxant and is considered a CNS (central nervous system) depressant. Naproxen is a NSAID (non-steroidal anti-inflammatory drug) and is not considered a CNS depressant.

Nevertheless, dizziness and drowsiness are potential side effects of naproxen, although they occur less commonly than with Flexeril. In addition, as naproxen is not a CNS depressant, there is no risk of more severe CNS side effects like respiratory depression.

According to the prescribing information for prescription strengths of naproxen, the following are possible side effects that relate to drowsiness:

  • Drowsiness (3—9%)
  • Vertigo (<3%)
  • Lightheadedness (<3%)
  • Dizziness (<3%)
  • Malaise (<1%)
  • Confusion (<1%)

So while you may experience some sedation with naproxen, it isn't overly common and is generally better tolerated in that regard than Flexeril.