Adverse reactions to naproxen mainly involve the GI tract. Constipation, heartburn, abdominal pain and nausea occur in about 3-9% of patients receiving the drug. Less frequently, dyspepsia, diarrhea, stomatitis, vomiting, anorexia and flatulence occur. Naproxen may reactivate latent peptic ulcer and may cause peptic ulcers in patients with no previous history of ulcers. Haemorrhage and perforation of ulcers may occur, occasionally causing fatalities, GI bleeding without obvious ulcer formation and melena have also occurred.
Adverse nervous system effects of naproxen include headache, drowsiness and dizziness, which occur in about 3-9% of patients. Vertigo, lightheadedness, inability to concentrate, mental depression, nervousness, irritability, fatigue, malaise, insomnia, sleep disorders and dream abnormalities may also occur.
Patients receiving naproxen have experienced tinnitus and less frequently, hearing or visual disturbances (e.g. hearing impairment). Adverse hematologic effects of naproxen include thrombocytopenia, leukocytopenia, granulocytopenia and eosinophilia. Naproxen can inhibit platelet aggregation and may prolong bleeding time. Pruritus, skin eruptions or rashes and ecchymoses occur frequently during naproxen administration.