progestagen use (oral, or depo-injectable drugs) which has been clearly linked to mammary fibroepithelial hyperplasia in cats. In a small proportion of cases, the disease occurs in neutered females or male cats with no exogenous progestagens having been administered. It is not clear if these cats also have excessive endogenous progesterone from another source. Spontaneous resolution of the condition typically (but not always) follows removal of the presumed source of progesterone (withdrawing drug therapy, neutering an entire female) but this can be very slow. If response is inadequate, or if there is not an obvious source of progestagens, administration of the progesterone receptor antagonist, aglepristone, has recently been reported to be highly successful. Doses used have been 10 mg/kg SC twice weekly or 20 mg/kg SC once weekly for 1–4 weeks, or 10 mg/kg SC daily for 4–5 days. | progestagen use (oral, or depo-injectable drugs) which has been clearly linked to mammary fibroepithelial hyperplasia in cats. In a small proportion of cases, the disease occurs in neutered females or male cats with no exogenous progestagens having been administered. It is not clear if these cats also have excessive endogenous progesterone from another source. Spontaneous resolution of the condition typically (but not always) follows removal of the presumed source of progesterone (withdrawing drug therapy, neutering an entire female) but this can be very slow. If response is inadequate, or if there is not an obvious source of progestagens, administration of the progesterone receptor antagonist, aglepristone, has recently been reported to be highly successful. Doses used have been 10 mg/kg SC twice weekly or 20 mg/kg SC once weekly for 1–4 weeks, or 10 mg/kg SC daily for 4–5 days. |