NSAID Use for Treating Dysmenorrhea and Preventing Chronic Pelvic Pain (NSAID HEAL)

Participants will receive Naproxen Sodium 550 mg oral tablet, administered twice daily for the first 48 hours of their menstrual period, for 1-year. Naproxen Sodium is a nonsteroidal anti-inflammatory drug (NSAID) used for pain relief and inflammation reduction. 550 mg naproxen sodium is the highest FDA-approved starting dosage, equivalent to 500 mg naproxen; the sodium formulation quickens absorption.

Participants will receive a placebo oral tablet, identical in appearance to Drug X, administered twice daily for the first 48 hours of their menstrual period, for 1-year. The placebo contains inactive ingredients with no known therapeutic effect.

Participants may take extended release acetaminophen 650mg oral tablet as needed for breakthrough menstrual pain. Participants will be instructed to take 1 dose of acetaminophen after 2 hours of taking a dose of either naproxen sodium or placebo, only if needed for pain relief. They are able to take an additional dose of acetaminophen after 2 more hours have elapsed for continued breakthrough symptoms. Use of rescue medication will be monitored and recorded.