Omeprazole is a member of a new class of antisecretory compounds termed the substituted benzimidazoles that act by inhibition of the H+/K+ ATPase enzyme system at the secretory surface of gastric parietal cells. Drugs inhibiting this enzyme system are often referred to as Proton Pump Inhibitors. The drug is primarily used in patients who have gastroesophageal reflux disease and in combination therapy for the treatment of Helicobacter pylori. Omeprazole is also useful for the treatment and prevention of non-steroidal anti-inflammatory drug (NSAID)-related gastroduodenal disease and peptic ulcer disease. Side effects include back and stomach pain, nausea, and skin rash.