Interactions between methaqualone and ethanol in rats and mice during acute and chronic states.

1. The effects of acute and chronic treatment of methaqualone on ethanol preference, the rate of disappearance of ethanol and on toxicity were studied in mice and rats. 2. Acute treatment with methaqualone showed a dose-dependent suppression in the voluntary intake of ethanol in C57Bl/6J mice in rats. No significant change in ethanol intake was observed during chronic methaqualone treatment and withdrawal. 3. Methaqualone pretreatment significantly (P less than 0.005) delayed the disappearance of ethanol in the blood and brain over a period of 50 and 200 min after a loading dose of 2.0 g/kg, i.p., of ethanol. 4. Methaqualone pretreatment at doses of 140 and 200 mg/kg significantly increased ethanol toxicity by 11% and 28%, respectively. Co-administration of ethanol using 6.0, 7.0 and 8.0 g/kg also reduced the LD50 of methaqualone by 19%, 24% and 40%, respectively. 5. Chronic administration with ethanol decreased the toxicity due to methaqualone. Potentiation of ethanol toxicity by methaqualone may be of clinical importance in view of the narrow range of safety margin of ethanol.