Altered respiratory control in newborn puppies after chronic prenatal exposure to alpha-1-acetylmethadol (LAAM).

Respiratory studies were conducted on newborn puppies chronically exposed to alpha-l-acetylmethadol . HCl (LAAM) during portions of gestation. Bitches received daily oral doses of LAAM from the second week through the sixth week of pregnancy (LAAM-6) or through the end of a 9-week pregnancy (LAAM-9), but not after parturition. LAAM-9 pups displayed narcotic abstinence signs during the first week after birth, while LAAM-6 pups did not. LAAM-9 pups had increased tidal volume, respiratory frequency, alveolar ventilation and O2-consumption and decreased alveolar CO2-tension during the first week of life compared to placebo-treated controls. The LAAM-9 CO2-response curve was significantly displaced to the left of control. These data are consistent with relative hyperventilation during neonatal withdrawal from LAAM. LAAM-6 pups had decreased tidal volume and alveolar ventilation during 4 of the 6 weeks studied. These changes in ventilation were associated with a decrease in O2 consumption. By 6 weeks after birth CO2-response curves of both LAAM-9 and LAAM-6 pups were shifted to the right of control. These changes in CO2-responsiveness suggest the possibility of prolonged disturbances of respiratory control which may continue beyond the sixth week of life.