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Citaat:

Cimeditine provides the greatest therapeudic benefit in equine patients with melanomas that are actively increasing in size and number. Its effect on melanomas that have not changed in size or appearance for many years is minimal. Cimetidine is administered orally at a dosage of 2.5 mg/kg three times daily. If the drug cannot be administered in this fashion, the total daily dose (7.5 mg/kg/day) can be divided into one or two daily doses, however horses treated every eight hours have responded (subjectively) best. If there is no change in the size or number of melanomas after three months of treatment, therapy should be discontinued. If there is a continual decrease in size and number of melanomas, therapy should continue until two to three weeks after a positive response is no longer apparent. The progression of the disease may be halted for months to years after the cessation of treatment, even if there was no clinically observable response to treatment.

Presently, there is no way to decide whether an individual horse will respond to treatment. A good response to treatment is typically characterized by a decrease of approximately 50% in the size and number of melanomas and no further progression of disease for several years. Changes in the number or size of melanomas during therapy typically become clinically discernible after two to seven weeks of treatment. In some horses, melanomas may again become active after months to years of disease quiescence. These horses often have a favorable response to cimetidine.

Cimetidine can also be used to decrease the chance of melanoma recurrence following cryonecrosis, surgical excision, or chemotherapy or to decrease the size and number of melanomas before surgical intervention. To date, no toxic effects of treatment with cimetidine have been reported in horses. Banning the expense and inconvenience of prolonged administration, cimetidine is a useful alternative in the clinical treatment of horses with melanomas. The usefulness of newer, more potent H2 antagonists is not known at this time.