Abstract

Chronic administration of methadone to pregnant rats is associated with an increase in mortality compared with either nontreated pregnant rats or treated nonpregnant rats. These observations would suggest some interaction between pregnancy and methadone administration. Treatment of the female during pregancy resulted in a decreased number of live offspring per litter, an increase in the percentage of stillborn pups, an increase in infant mortality and a retardation of growth of the pups nursing treated mothers. There was a dose-response relationship in most parameters at the lower doses used but at higher dose levels the dose-response was not as obvious. The overall effect of methadone on reproduction was seen as an increase in the number of maternal deaths, a decrease in the number of pups born per litter and a decrease in the number of pups weaned. One hundred and forty-eight pups were weaned from 20 control animals while 20 animals in each of the three treated groups, 2.5, 5 and 7.5 mg/kg of methadone, raised 78, 42 and 41 pups, respectively, to weaning age.