NEMBUTAL® Sodium Solution (pentobarbital sodium injection) is a sterile solution for intravenous or intramuscular injection. NEMBUTAL® Sodium is a short-acting barbiturate, chemically designated as sodium 5-ethyl-5-(1- methyl butyl) barbiturate. Each mL contains pentobarbital sodium 50 mg, in a vehicle of propylene glycol, 40%, alcohol, 10% and water for injection, to volume.