Gastric side effects of anti-inflammatory drugs. Illustration of an arthritic knee and a stomach. Non-steroidal anti-inflammatory drugs (NSAID) are often used as a long-term treatment for pain in arthritic patients. Common side effects of NSAID use are gastrointestinal problems, including indigestion, abdominal pain and stomach ulcers. Ulcers are open sores in the stomach lining. Complications of stomach ulcers include internal bleeding and perforation of the stomach wall, both of which can be fatal.