Potentiation of pentobarbitone sleeping time by chloroquine in the rat

The effects of chronic administration of chloroquine on pentobarbitone sleeping time was studied in albino rats. Administration of chloroquine (20 mg/kg s.c.) for 21 days significantly increased pentobarbitone sleeping time by 16--105% within that period. A combination of chloroquine (20 mg/kg s.c.) and pentobarbitone (20 mg/kg s.c.) not only antagonised the usual decreased pentobarbitone sleeping time when pentobarbitone is given alone but also increased it by 34--56% within 7--14 days. In chloroquine chronic pretreated rats injection of sub-anaesthetic doses of pentobarbitone (20 mg/kg i.p.) produced anaesthesia for 42.15 +/- 4.6 min while untreated rats became only ataxic. It has been suggested that these effects of chloroquine may be due to a decrease in the metabolism of pentobarbitone in the liver.