Barbiturate anesthesia is thought to be produced by the combined effect of enhanced inhibition and diminished excitation. The distinction between an anesthetic and an anticonvulsant barbiturate depends on the concentration at which amino acids modulation and GABA-mimicking activities occur. Pentobarbital sodium occurs as white powder or crystalline granules that are freely soluble in water or alcohol to form a clear, colorless solution. The wide use of pentobarbital in rodents stems from its generalized availability, modest cost, widely available database for its use, rapid anesthetic onset, nonirritant nature, and ease of intraperitoneal injection to rodents of varying ages and body weights. Pentobarbital is a relatively poor analgesic.
Higher doses are necessary to provide a surgical plane of anesthesia.
A mild excitement phase, during both anesthetic induction and recovery, is often observed with pentobarbital anesthesia. Pentobarbital causes respiratory depression which may result in hypercapnia with decreased tidal volume, minute volume, and respiratory rate. Reduced blood pressure, stroke volume, pulse pressure, and central venous pressure are common findings in pentobarbital-anesthetized animals. In prolonged anesthesia, the drug has also been shown to cause impaired myocardial contractility. Other reported effects include progressive decrease in core body temperature, decreased renal blood flow, reduced glomerular filtration rate, decreased intraocular pressure, and decreased urine output.