PURPOSE: Consumer surveys have identified an over-the-counter (OTC) medication that provides complete and long-lasting relief of frequent heartburn as an unmet consumer need. The purpose of the two identical studies reported in this paper was to evaluate the safety and effectiveness of 10.3 and 20.6 mg omeprazole magnesium, referred to as Ome-Mg 10 and Ome-Mg 20, respectively (equivalent to 10 and 20 mg omeprazole) for the treatment of frequent heartburn administered as a novel 14-day OTC regimen. SUBJECTS AND METHODS: Subjects with frequent heartburn (heartburn two or more days per week) took Ome-Mg 10, Ome-Mg 20, or placebo for 14 consecutive mornings. Statistical analyses compared percentage of subjects with no heartburn 24 h after the first dose, after the last dose (day 14), and percentage of days that subjects were heartburn-free. Nocturnal heartburn and heartburn rated no more than mild were also assessed. RESULTS: Twenty-four hours following the first dose, nearly 50% of subjects receiving Ome-Mg 20 reported no heartburn, and more than 80% receiving Ome-Mg 20 had no more than mild heartburn. Both doses were significantly more effective than placebo on days 1 and 14 for percentage of subjects heartburn-free for 24 h (P < or = 0.003), and across all 14 days for percentage of heartburn-free days (P < 0.001). Ome-Mg 20 was significantly more effective than placebo in preventing nocturnal heartburn across all 14 days (P < 0.001). Ome-Mg was well tolerated. CONCLUSION: These trials demonstrated the safety and effectiveness of a novel 14-day regimen of Ome-Mg 20 in completely preventing heartburn for 24 h establishing it as an excellent self-care treatment for frequent heartburn and supporting the approval of Prilosec OTC.