Adults

For mild to moderate pain, dysmenorrhea, or acute tendonitis/bursitis: 250-500 mg twice daily. For rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis: 250-500 mg twice daily. Maximum daily dose is 1000 mg (or 1500 mg for short-term acute use).

Elderly

Lower doses may be required, and renal function should be monitored. Start with the lowest effective dose.

Renal_impairment

Use with caution. Consider reduced doses and monitor renal function. Avoid in severe renal impairment (CrCl <30 mL/min).

Onset

Analgesic effect typically within 1 hour, anti-inflammatory effects may take up to 2 weeks.

Excretion

Primarily excreted in the urine (about 95% as naproxen, 6-O-desmethylnaproxen, and their glucuronide conjugates). A small amount is excreted in the feces.

Half life

Approximately 12-17 hours, allowing for twice-daily dosing.

Absorption

Rapidly and completely absorbed from the GI tract. Peak plasma concentrations are achieved in 2-4 hours. Food can delay but does not significantly reduce absorption.

Metabolism

Extensively metabolized in the liver by cytochrome P450 enzymes, primarily to 6-O-desmethylnaproxen, which is then glucuronidated.

SSRIs

Increased risk of GI bleeding.

Lithium

Increased plasma lithium levels and toxicity.

Methotrexate

Increased methotrexate toxicity.

Corticosteroids

Increased risk of GI ulceration and bleeding.

Other NSAIDs or Aspirin

Increased risk of gastrointestinal adverse effects.

Diuretics (e.g., Furosemide)

Reduced diuretic and antihypertensive effects.

Anticoagulants (e.g., Warfarin)

Increased risk of bleeding.

ACE inhibitors and Angiotensin II receptor blockers

May reduce antihypertensive effect and increase risk of renal impairment.