1992 Volume 45 Issue 3 Pages 191-194
The efficacy of subcutaneous implantation of 20%(w/w) norethisterone (NET) in silastic silicon rubber was examined for suppressing estrus in dogs. Of a total of 11 bitches, 10 received NET ranging from 5 to 50mg/kg and one received only the rubber without NET, as a control. The suppressive effect of NET on estrus was confirmed in bitches that received NET at 10mg/kg or more, but not in bitches with a dose of 5 mg/kg. The period from implantation to recovery of estrus was dose-dependent, 11 to 19months for the dose of 10 to 15mg/kg and 27 to 29months for 25 to 30mg/kg. No estrus was observed during the observation period of 33months in bitches receiving 40 or 50mg/kg. After the recovery of estrus in 3 bitches receiving 10 or 15mg/kg, one bitch had become pregnant by spontaneous mating and was delivered of 5 normal puppies, but the other 2 bitches had become sterile.