Body weight gain and food and water consumption of female rats receiving daily methadone injections (5 mg/kg) intraperitoneally prior to mating and during gestation and lactation were studied. In contrast to saline-injected mothers, methadone-treated females had lower body weights throughout pregnancy, but gained weight during lactation; by postnatal day 21, both groups were of comparable body weight. No significant differences in food consumption throughout gestation or lactation were recorded. Total water consumption of methadone-treated rats was higher during the first 2 weeks of gestation and lactation, and lower during the 3rd week of lactation when compared to controls. These results demonstrate that methadone-treated rats have lower body weights throughout gestation and lactation, and that these weight deficits are not caused by insufficient food and water consumption.
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