Self-administration of barbiturates and benzodiazepines: a review.

Studies of barbiturate and benzodiazepine self-administration are categorized by species and route of administration. Reinforcement, defined as self-administration of drug greater than of a non-drug control, has been demonstrated most often in studies employing the IV route, and there has been greater reliability in this result for a given drug among barbiturates rather than among benzodiazepines. Most studies of PO self-administration in rodents have not demonstrated reinforcement, despite a number of behavioral manipulations to induce drug intake. Studies of PO barbiturate self-administration in monkeys have demonstrated reinforcement but recent studies of PO benzodiazepine self-administration in baboons have not, although physical dependence was demonstrated. Reinforcement via the IG route has not been reliably demonstrated. Behavioral variables, including interreinforcement interval and drug self-administration history, appear to be important determinants of whether or not reinforcement will be demonstrated, particularly among the benzodiazepines; but the range of conditions under which behavioral and pharmacological variables interact to promote or lessen the likelihood of self-administration of these drugs remains to be determined experimentally.