Buspirone hydrochloride (abbr. to BH), an anxiolytic drug, was examined for its intravenous, subcutaneous or oral acute toxicity using Crj : CD-1 (ICR) mice, Crj : CD (Sprague-Dawley) rats and beagle dogs of both sexes. The results obtained were summarized as follows : 1.Drug-related toxic signs included decreased activity and convulsions accompanied with salivation and opisthotonus in mice and rats treated with BH regardless of administration routes, and tremors and clonic convulsions accompanied with salivation in dogs treated with BH orally. 2. Pathological examinations revealed distention of the stomach in dead rats treated with BH orally, and hypersecretion of gastric juice and alterations (viz. edema, necrosis and petechia) on the superficial mucous membrane in the gastropyloric region in dead dogs treated with BH orally. 3. The cause of death was considered to be due to respiratory insufficiency in every species of animals examined. 4. LD50 values (mk/kg) were as follows : [table] 5. No sex differences were observed in every species of animals regardless of administration routes on the basis of toxicological parameters examined.

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Buspirone hydrochloride(buspirone) and buspirone-ovalbumin mixture were examined for their antigenicity in guinea pigs and mice in comparison with ovalbumin (OVA) and 2, 4-dinitrochlorobenzene (DNCB)-OVA conjugate. The results obtained were as follows : 1. When guinea pigs were sensitized with buspirone or buspirone-OVA emulsified with Freund's complete adjuvant (FCA), these animals showed negative reactions in active systemic anaphylaxis (ASA), active cutaneous anaphylaxis (ACA), passive cutaneous anaphylaxis (PCA), passive hemagglutination (PHA) and Schultz-Dale test. 2. When mice were sensitized with buspirone or buspirone-OVA adsorbed to alum, these animals revealed a negative reaction in PCA using rats. 3. As positive controls, guinea pigs were sensitized with OVA or DNCB-OVA emulsified with FCA, and mice with OVA or DNCB-OVA adsorbed to alum. As a result, these animals disclosed positive reactions in ASA, ACA, PCA, PHA and Schultz-Dale test. As shown above, buspirone was considered to possess neither antigenic nor haptenic properties.

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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.

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Buspirone hydrochloride (buspirone), an anxiolytic drug, was administered orally to pregnant Crj: CD (Sprague-Dawley) rats from day 17 of gestation through day 20 of postpartum at dose levels of 2, 12 and 75 mg/kg/day. The summarized results obtained are as follows : 1. Decrdased 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 buspirone 12 mg/kg and higher. 2. Brain and adrenal weights were increased in F₀ dams at buspirone 12 mg/kg and higher. Besides, lung and pituitary weights were augmented in F₀ dams at buspirone 75 mg/kg. 3. Buspirone 75 mg/kg brought the increased number of stillbirths in F₁ neonates. 4. Buspirone 75 mg/kg lowered the viability of newborns (F₁) on postnatal day 3 and prolonged the days required for pinnae detachment, presence of abdominal hair and eye opening in offspring (F₁), but failed to function their learning ability, motility, motor activity or emotional development. 5. Body weight gains were depressed in both male and female F₁ rats at buspirone 12 mg/kg and higher. Food consumption was also decreased in both sexes at the same dose levels. 6. Heart weights were decreased in female F₁ rats after mating at buspirone 12 mg/kg and higher. Further, buspirone 75 mg/kg brought a suppression of brain weights at 10 weeks of age in male and female F₁ rats, but failed to affect their reproductive ability. 7. F₂ neonates derived from F₁ rats whose dams had ever received buspirone during the perinatal and lactation periods 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.

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