Source: FDA, National Drug Code (US) Revision Year: 2020
In animals, diazepam appears to act on parts of the limbic system, the thalamus and hypothalamus, and induces calming effects. Diazepam, unlike chlorpromazine and reserpine, has no demonstrable peripheral autonomic blocking action, nor does it produce extrapyramidal side effects. However, animals treated with diazepam do have a transient ataxia at higher doses. Diazepam was found to have transient cardiovascular depressor effects in dogs. Long-term experiments in rats revealed no disturbances of endocrine function. Injections into animals have produced localized irritation of tissue surrounding injection sites and some thickening of veins after intravenous use.
A study performed in 24 healthy male subjects comparing the I.M. Injection of 10 mg of diazepam in the mid-anterior/lateral thigh by the autoinjector versus 10 mg I.M. by a syringe (operated manually) indicates that the mean percent availability of the drug from the autoinjector is 100% of that obtained from the syringe.
In addition, the mean Cmax value from the autoinjector was 314 ng/mL (c.v. = 18.7%, range 185 to 439 ng/mL) and 48.6 ng/mL (c.v. = 19.8%, range 29.4 to 69.7 ng/mL) for diazepam and desmethyldiazepam, respectively, while the syringe gave corresponding values of 287 ng/mL (c.v. = 18.9%, range 174 to 378 ng/mL) and 47.2 ng/mL (c.v. = 19.4%, range 33.1 to 61.2 ng/mL) for diazepam and desmethyldiazepam, respectively.
The corresponding mean Tmax values were 1.47 hours (c.v. = 69.9%, range 0.8 to 6 hours) and 61.0 hours (c.v. = 56.8%, range 24 to 144 hours) for diazepam and desmethyldiazepam for the autoinjector whereas the syringe gave values of 1.31 hours (c.v. = 32%, range 0.7 to 2.0 hours) and 54.5 hours (c.v. = 47.3%, range 12 to 96 hours) for diazepam and desmethyldiazepam, respectively.
Oral LD50 of diazepam is 720 mg/kg in mice and 1240 mg/kg in rats. Intraperitoneal administration of 400 mg/kg to a monkey resulted in death on the sixth day.
A series of rat reproduction studies was performed with diazepam in oral doses of 1, 10, 80 and 100 mg/kg given for periods ranging from 60-228 days prior to mating. At 100 mg/kg there was a decrease in the number of pregnancies and surviving offspring in these rats. These effects may be attributable to prolonged sedative activity, resulting in lack of interest in mating and lessened maternal nursing and care of the young. Neonatal survival of rats at doses lower than 100 mg/kg was within normal limits. Several neonates, both controls and experimentals, in these rat reproduction studies showed skeletal or other defects. Further studies in rats at doses up to and including 80 mg/kg/day did not reveal significant teratological effects on the offspring. Rabbits were maintained on doses of 1, 2, 5 and 8 mg/kg from day 6 through day 18 of gestation. No adverse effects on reproduction and no teratological changes were noted.
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