Separation of hepatic N-demethylase-inducing and opioid dependence-producing doses of levo-alpha-acetylmethadol in the pregnant rat.

A 2.0 mg per kg oral dose of 1-alpha-acetylmethadol (LAAM) administered daily to female rats prior to mating and throughout pregnancy increased ethylmorphine N-demethylase activity in liver microsomes of the dams measured 24 h after parturition. This dose of LAAM decreased maternal weight gain during gestation and increased postnatal mortality. However, 0.05 mg LAAM per kg was sufficient to produce dependence in the dams without affecting hepatic drug metabolism, gestational weight gain or neonatal mortality. The data indicate that it is not necessary to use doses of LAAM which can affect drug metabolizing enzymes in dams and increase pup mortality to maintain opioid-type physical dependence.