Cimetidine INN is a histamine H2-receptor antagonist that inhibits stomach acid production. It is largely used in the treatment of heartburn and peptic ulcers.

Uses
In some studies, cimetidine has been found to reduce the debilitating pain and symptoms of herpes zoster, presumably by blocking the H2-receptors of T-lymphocyte suppressor cells.

There has been some evidence to suggest cimetidine could be effective in the treatment of common warts, but more rigorous double-blind clinical trials suggested it to be no more effective than a placebo.

Another study by Yokoyama, et al., used cimetidine for the treatment of chronic calcific tendinitis of the shoulder. The small scale study took 16 individuals with calcific tendinitis in one shoulder, all of which had previously attempted other forms of therapy, including steroid injection and arthroscopic lavage. During the course of the study, 10 patients reported an elimination of pain and 9 displayed a complete disappearance of calcium deposits. With results being on a small scale, cimetidine, for the treatment of chronic calcific tendinitis of the shoulder, has been recommended to be opened to large scale clinical trials.

In Asia, cimetidine, which molecularly targets EGF, VEGF and e-selectin associated with sialylated Lewis biomarkers and metastasis, has been combined with long term, continuous low dose 5FU or metronomic tegafur-uracil chemotherapy for advanced epithelial cancers, with unusually long survival including for stage III colorectal cancers, as well as refractory and recurrent cancers.

Cimetidine has been reported for use as an analgesic in experimental treatments of interstitial cystitis.

Pretreatment with cimetidine improves the accuracy of measured creatinine clearance testing when using urine collection analysis.