REPRODUCTIVE AND DEVELOPMENTAL TOXICITY STUDIES OF BUSPIRONE HYDROCHLORIDE (I) : Oral Administration to Rats During the Period of Fetal Organogenesis

Buspirone hydrochloride (buspirone), an anxiolytic drug, was administered orally to pregnant Crj : CD (Sprague-Dawley) rats from day 7 through 17 of gestation at dose levels of 2, 12 and 75 mg/kg/day. The summarized results obtained are as follows : 1. Decreased activity was observed for F0 dams at buspirone 75 mg/kg. Further, the suppression of maternal body weight gains accompanied by the reduction of food consumption was shown during the administration period at the same dose level. 2. Liver weights were increased in F0 dams at term at buspirone 12 mg/kg and higher. Besides, brain, pituitary, adrenal and ovarian weights were increased in F0 dams at term at buspirone 75 mg/kg. 3. Buspirone 75 mg/kg brought the inhibition of fetal growth followed by the lowered values in fetal weights, crown-rump distances and tail lengths. Furthermore, the elevated incidence of skeletal abnormalities such as nodulated and wavy ribs and unossified 5th and 6th sternums, as well as retarded ossification of cervical vertebrae, forelimbs and hindlimbs were also noted in this dose level. Also, the retarded ossification was observed at 12 mg/kg. 4. Buspirone failed to affect the parturition of F0 dams. 5. Buspirone did not function the viability of newborns (F1), and postnatal differentiations, learning ability, motility, motor activity or emotional development in F1 animals. 6. Body weight gains were depressed in female F1 rats from 4 to 9 weeks of age and food consumption was decreased in male F1 rats from 6 to 8 weeks of age at buspirone 75 mg/kg. 7. Buspirone 75 mg/kg produced suppressions of brain weights at 10 weeks of age in male and female F1 rats and lung weights at weaning in male F1 rats. Spleen weights were increased in female F1 rats at 10 weeks of age at the same dose level. However buspirone failed to affect their reproductive ability. 8. F2 neonates derived from F1 rats whose dams had ever received buspirone during the period of fetal organogenesis showed no changes in observation items at birth. Based on these results, the no-effect dose level of oral buspirone under the present experimental condition was estimated to be 2 mg/kg/day against dams and their offspring.