Barbiturates are medicines that act on the central nervous system. They cause drowsiness and can control seizures.


Barbiturates are in the group of medicines known as central nervous system depressants (CNS). Also known as sedative-hypnotic drugs, barbiturates make people very relaxed, calm, and sleepy. These drugs are sometimes used to help patients relax before surgery. Some may also be used to control seizures (convulsions). Although barbiturates have been used to treat nervousness and sleep problems, they have generally been replaced by other medicines for these purposes.

Although barbiturates have largely been replaced by other classes of drugs, some are still used in anesthesiology to induce anesthsia and lower the dose of inhaled anesthetics required for surgical procedures.

Pentobarbital (Nembutal) has been used in neurosurgery to reduce blood flow to the brain. This reduces swelling and pressure in the brain, making brain surgery safer.

Secobarbital (Seconal) may be given by mouth or as a suppository to induce sleepiness and relaxation before local anesthesia or the insertion of a tube into the nose or throat.

These medicines may become habit-forming and should not be used to relieve everyday anxiety and tension or to treat sleeplessness over long periods.


Barbiturates are available only with a physician's prescription and are sold in capsule, tablet, liquid, and injectable forms. Some commonly used barbiturates are phenobarbital (Barbita) and secobarbital (Seconal).

Recommended dosage

Recommended dosage depends on the type of barbiturate and other factors such as the patient's age and the condition for which the medicine is being taken. The patient should consult with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage.

The following recommendations do not apply when barbiturates are given as a single oral or intravenous dose prior to or during surgery. The recommendations should be considered if the drugs are used for treatment of anxiety or seizures.

Patients should always take barbiturates exactly as directed. Larger or more frequent doses should never be taken, and the drug should not be taken for longer than directed. If the medicine does not seem to be working, even after taking it for several weeks, the patient should not increase the dosage. Instead, the physician who prescribed the medicine should be consulted.

People taking barbiturates should not stop taking them suddenly without first checking with the physician who prescribed the medication. It may be necessary to taper the dose gradually to reduce the chance of withdrawal symptoms. If it is necessary to stop taking the drug, the patient should check with the physician for instructions on how to stop.


People taking barbiturates must see a physician regularly. The physician will check to make sure the medicine is working as it should and will note unwanted side effects.

Because barbiturates work on the central nervous system, they may add to the effects of alcohol and other drugs that slow the central nervous system, such as antihistamines, cold medicine, allergy medicine, sleep aids, medicine for seizures, tranquilizers, some pain relievers, and muscle relaxants . They may also add to the effects of anesthetics, including those used for dental procedures. The combined effects of barbiturates and alcohol or other CNS depressants (drugs that slow the central nervous system) can be very dangerous, leading to unconsciousness or even death. Anyone taking barbiturates should not drink alcohol and should check with his or her physician before taking any medicines classified as CNS depressants.

Taking an overdose of barbiturates or combining barbiturates with alcohol or other central nervous system depressants can cause unconsciousness and even death. Anyone who shows signs of an overdose or a reaction to combining barbiturates with alcohol or other drugs should get emergency medical help immediately. Signs include:

Barbiturates may change the results of certain medical tests. Before having medical tests, anyone taking this medicine should alert the health care professional in charge.

People may feel drowsy, dizzy, lightheaded, or less alert when using these drugs. These effects may even occur the morning after taking a barbiturate at bedtime. Because of these possible effects, anyone who takes these drugs should not drive, use machines or do anything else that might be dangerous until they have found out how the drugs affect him or her.

Barbiturates may cause physical or mental dependence when taken over long periods. Anyone who shows these signs of dependence should check with his or her physician right away:

Children may be especially sensitive to barbiturates. This sensitivity may increase the chance of side effects such as unusual excitement.

Older people may also be more sensitive than others to the effects of this medicine. In older people, barbiturates may be more likely to cause confusion, depression, and unusual excitement. These effects are also more likely in people who are very ill.

Special conditions

People with certain medical conditions or who are taking certain other medicines can have problems if they take barbiturates. Before taking these drugs, be sure to let the physician know about any of these conditions:

ALLERGIES. Anyone who has had unusual reactions to barbiturates in the past should let his or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

PREGNANCY. Taking barbiturates during pregnancy increases the chance of birth defects and may cause other problems such as prolonged labor and withdrawal effects in the baby after birth. Pregnant women who must take barbiturates for serious or life-threatening conditions should thoroughly discuss with their physicians the benefits and risks of taking this medicine.

BREASTFEEDING. Barbiturates pass into breast milk and may cause problems such as drowsiness, breathing problems, or slow heartbeat in nursing babies whose mothers take the medicine. Women who are breast-feeding should check with their physicians before using barbiturates.

OTHER MEDICAL CONDITIONS. Before using barbiturates, people with any of these medical problems should make sure their physicians are aware of their conditions:

USE OF CERTAIN MEDICINES. Taking barbiturates with certain other drugs may affect the way the drugs work or may increase the chance of side effects.

Side effects

The most common side effects are dizziness, lightheadedness, drowsiness, and clumsiness or unsteadiness. These problems usually go away as the body adjusts to the drug and do not require medical treatment unless they persist or interfere with normal activities.

More serious side effects are not common, but may occur. If any of the following side effects occur, the physician who prescribed the medicine should be contacted immediately:

In addition, if confusion, depression, or unusual excitement occur after taking barbiturates, a physician should be contacted as soon as possible.

Patients who take barbiturates for a long time or at high doses may notice side effects for some time after they stop taking the drug. These effects usually appear within eight to 16 hours after the patient stops taking the medicine. If these or other troublesome symptoms occur after stopping treatment with barbiturates, a physician should be contacted:

Other side effects may occur. Anyone who has unusual symptoms during or after treatment with barbiturates should consult with his or her physician.


Birth control pills may not work properly when taken while barbiturates are being taken. To prevent pregnancy, additional methods of birth control are advised while taking barbiturates.

Barbiturates may also interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes barbiturates should let the physician know all other medicines he or she is taking. Among the drugs that may interact with barbiturates are:

The list above does not include every drug that may interact with barbiturates. A physician or pharmacist should be consulted before combining barbiturates with any other prescription or nonprescription (over-thecounter) medicine.



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Karch, A. M. Lippincott's Nursing Drug Guide. Springhouse, Penn: Lippincott Williams & Wilkins, 2003.

Reynolds, J. E. F., ed. Martindale The Extra Pharmacopoeia 31st Ed. London: The Pharmaceutical Press, 1993.


Miller, Norman S. "Sedative-Hypnotics: Pharmacology and Use." Journal of Family Practice 29 (December 1989): 665.

Nancy Ross-Flanigan

Sam Uretsky

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