An experimental investigation of dependence liability of methaqualone in rats

In the present study, rats were kept on a semifluid diet, and methaqualone and phenobarbitone were added to the diet of different groups of animals. Every week the doses of the drugs were increased and daily records of body weight, mean rectal temperature and spontaneous motor activity were maintained. Tolerance to both the drugs was discernible in the first and second week, when the animals received 138.3 and 284.4 mg/kg/day of methaqualone and 96.8 and 178.6 mg/kg/day of phenobarbitone, respectively. In the third week the doses were further increased to 392.6 mg/kg/day of methaqualone and 235.9 mg/kg/day of phenobarbitone and at the end of this week although there was gradual and partial recovery, statistically significant (P<0.05) lowering of mean rectal temperature, body weight and spontaneous motor activity was observed in comparison to a control group of rats. After the third week when the drugs were withdrawn from the diet methaqualone treated rats exhibited increased susceptibility to audiogenic stimuli. Rats similarly treated with phenobarbitone showed a greater susceptibility to audiogenic stimuli, and in addition exhibited increased motor activity and a precipitous decrease in body weight. The results of this study are suggestive of a milder degree of dependence liability in methaqualone as compared with barbiturates.