Cimetadine is a histamine H2-receptor antagonist that inhibits stomach acid production. It is frequently sold over the counter for use in humans and animals for the treatment of heartburn and peptic ulcers. Cimetadine works by blocking the action of histamine and reducing acid in the stomach. Cimetidine may be used to aid in the treatment of existing ulcers and help prevent the development of ulcers. It may also be used in the treatment of reflux or to reduce inflammation of the esophagus or stomach.

Cimetadine is also given to help slow the progressive growth of melanomas in gray horses, when provided as a daily supplement in feed.

Dosage: 2.5 mg/kg, PO q8h (for melanoma control), 12-20 mg/kg, PO, q8h; 18 mg/kg, PO q12h (H2 blocker)