Cimetidine is a histamine H2 blocker. This drug prevents the release of acid into the stomach.

Famotidine is a white to pale yellow crystalline compound that is freely soluble in glacial acetic acid, slightly soluble in methanol, very slightly soluble in water, and insoluble in ethanol.

Omeprazole is a proton pump inhibitors (PPI) which blocks the production of acid by the stomach. This drug suppresses gastric acid secretion relieving gastrointestinal distress and promoting ulcer healing.

Ranitidine is an H2 blocker that blocks the action of histamine on stomach cells thereby reducing stomach acid production.