This is the prototypic BARBITURATE central nervous system (CNS) DEPRESSANT. It is prescribed and sold as Luminal and was introduced into clinical medicine in 1912. It was used for a long period as a SEDATIVE-HYPNOTIC drug but has now largely been replaced by the much safer BENZODIAZEPINES.

Phenobarbital's long duration of action makes it useful for treating many forms of general and partial seizure disorders, such as epilepsy. Chronic use can result in TOLERANCE AND PHYSICAL DEPENDENCE, so it is classified as a Schedule III drug in the CONTROLLED SUBSTANCES ACT. Chronic treatment with phenobarbital can increase the activity of certain liver enzymes that metabolize other drugs. Thus a potential side effect is that other drugs (e.g., steroids, oral anticoagulants, digitoxin, beta-blockers, oral contraceptives, phenytoin, and others) are metabolized more quickly—and their effectiveness is reduced. Combinations of pheno-barbital and other CNS depressants, such as ALCOHOL (ethanol), can lead to severe motor impairment and reduced breathing.

Figure 1 Phenobarbital

See Also

Drug Metabolism; Drug Interactions and Alcohol)

Bibliography

HARVEY, S. C. (1975). Hypnotics and sedatives. In L. S. Goodman & A. Gilman (Eds.), The Pharmacological basis of therapeutics, 5th ed. New York: Macmillan.