They cause sedation, hypnosis, basal narcosis, general anesthesia and coma depending on the agent and the dosage. Animals given these drugs will go through an excitement stage before becoming anesthetized as the higher centers of the brain are depressed and lower centers take over. Individuals delivering these drugs should be aware that overdosage may cause respiratory and circulatory failure and death. Since barbiturates cross placental barriers, fetal depression will result. Care should be taken to maintain body temperature.
Recovery is slow and varies with species and dosage.
Concurrent use of a premedication with low doses of analgesics and tranquilizers can decrease the amount of barbiturate needed and reduce effects on respiratory, cardiac and temperature regulating centers. These agents must be given intravenously. Perivascular injection results in severe irritation and sloughing of soft tissues. Dissociative anesthetics are discussed under the previous section on chemical restraint. Ketamine can be used alone but, in combination with a phenothiazine tranquilizer or with xylazine, general anesthetic results are more satisfactory.