Naproxen is a non-steroidal anti-inflammatory medicine (NSAID) used to relieve the pain and inflammation caused by acute gout attacks. Take it with food exactly as prescribed to reduce stomach irritation and complete the recommended course. Common side effects include indigestion, stomach pain, nausea and heartburn. Avoid taking other NSAIDs unless advised, and seek medical attention immediately if you notice black stools, vomiting blood or severe stomach pain.