Histopathological studies of subcutaneous implantation of chlormadinone acetate (CMA) for preventing estrus in queens.

The efficacy and clinical safety of chlormadinone acetate (CMA) in preventing estrus were assessed in queens on condition that CMA was subcutaneously implanted in siliastic rubber. Thirteen queens were divided into the following four groups according to dose of CMA-administered: group 1 (n = 3), control; group 2 (n = 3), 2.5 mg/kg; group 3 (n = 3), 5 mg/kg; group 4 (n = 4), 20 mg/kg. The implants were left in these queens for 12 months after implantation. All control animals showed signs of estrus during the experiment, with periods of anestrus of normal duration. In contrast, estrus was completely inhibited in the CMA-treated groups. Histopathologically, the uterus from group 4 had coiled branched glands with little secretion in the endometrium. Mammary glands from the CMA-treated groups showed mild lobular development with acinar proliferation and secretion. Sections through the other organs (pituitary gland, adrenal gland, ovary, and implant site) had no distinct or consistent changes that could be related to the CMA-treated. It was concluded, therefore, subcutaneous implantation of CMA could be the good drug-delivery system for reducing changes due to the antigonadotropic and glucocorticoid-like activities and serious condition in the uterine and mammary gland due to progestagenic activity.