Progestational potency of chlormadinone acetate in the immature beagle bitch: Preliminary report

• Published in: Contraception (Stoneham) Vol. 2; no. 6; pp. 381 - 390
• Main Authors: Hill, R., Averkin, E., Brown, W., Gagne, W.E., Segre, E.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1970
• ISSN: 0010-7824; 1879-0518
• DOI: 10.1016/S0010-7824(70)80001-4

Chlormadinone acetate (CAP) and norethindrone (NET) were administered orally to immature, estradiol benzoate-primed beagle bitches. The progestational activity of these compounds was compared by measuring uterine/body weight ratios and by scoring uterine morphological responses. On the basis of uterine/body weight ratios, CAP was 225 times more potent as a gestogen than was NET. By McPhailtype scoring the potency of CAP was 62 times that of NET and by a comparative method ranking uterine morphological responses the relative progestational potency of CAP to NET was 82. It has been reported that CAP has about 5 times the progestational potency of NET in man. The present study demonstrates that there is a marked interspecies difference in the relation of these two compounds. The importance of establishing pharmacologically analogous doses (PAD) before initiating toxicity studies in experimental animals is emphasized.