The effect methoxsalene on hypnotic and subhypnotic doses of pentobarbital.

The effect of several doses of methoxsalen on hypnotic action of 40 mg/kg of pentobarbital in mice was studied. Methoxsalen was injected 30 minutes before the barbiturate. The highest methoxsalen dose of 22 mg/kg extended the duration of the hypnotic action of pentobarbital about 10 times compared to the control. The effect decreased with time, and 96 hours after this single dose of methoxsalen it was not significantly different from that observed with the control animals receiving only 40 mg/kg pentobarbital. The other methoxsalen doses (10, 5, and 2 mg/kg) exhibited an equal effect on the hypnotic action of pentobarbital, and only in the first measuring time. The effect could not be detected after 24 hours, and no dose dependence was observed. Small doses of methoxsalen of 2 and 1 mg/kg injected 30 minutes before a subhypnotic pentobarbital dose of 30 mg/kg produced sleep in 75% of animals of the both groups. In the control group, this dose produced no sleep in none of the animals.