The effectiveness of low-dose omeprazole as primary prevention of gastrointestinal adverse events due to episodic use of non-selective NSAIDs was evaluated. Healthy adults aged 50-75 who did not take chronic NSAIDs were randomized to a 6.5-day treatment of naproxen 500 mg twice daily plus omeprazole 20 mg daily or naproxen 500 mg twice daily plus placebo. Seventy subjects were enrolled (mean age 58.6 years, proportion >60 = 41.4%). Subjects receiving naproxen plus omeprazole developed fewer gastroduodenal ulcers compared to subjects receiving naproxen plus placebo (11.8% vs. 46.9%, P = 0.002). Likewise, naproxen plus omeprazole was associated with a decreased risk of ulceration and/or >5 erosions (38.2% vs. 81.3%, P < or = 0.001), and a smaller change in dyspepsia score. Considering their relatively low cost, ready availability, and favorable safety profile, low-dose PPI co-prescription in healthy adults requiring short-term therapy with non-selective NSAIDs may be reasonable.