Proton pump inhibitors (omeprazole, lansoprazole, pantoprazole, rabeprazole, esomeprazole) are commonly used for the treatment of gastro-oesophageal reflux disease and other acid-related gastrointestinal disorders as well. They all have a broadly similar mechanism of action and are metabolised in the liver via cytochrome P450 (CYP). They all have proved to be highly effective and generally safe. Different activation rates, binding sites within the H⁺/K⁺-ATPase and contribution of each CYP isoenzyme in their metabolism may produce differences in the potential for drug interactions and toxicity as well as onset and level of acid suppression. However, there is very little evidence to state that the differences in clinical efficacy of the five proton pump inhibitors are significant.