Barbiturates
Barbiturates
Definition
Barbiturates are a large class of drugs, consisting of many different brand-name products with generic equivalents, which are used primarily for mild sedation, general anesthesia, and as a treatment for some types of epilepsy. One barbiturate, butalbital, exists only as a component of headache preparations that also include acetaminophen and sometimes caffeine. The most common members of the barbiturate family are phenobarbital (Luminal), pentobarbital (Nembutal), amobarbital (Amytal), secobarbital (Seconal), thiopental (Pentothal, Sodium Pentothal, also colloquially known as “truth serum”), methohexital (Brevital), and butalbital (a component of Fiorinal and Fioricet). They exist in numerous formulations and strengths.
Purpose
Barbiturates are used to sedate patients prior to surgery as well as to produce general anesthesia, to treat some forms of epilepsy, and to treat simple and migraine headache. These drugs are highly addictive and are often abused as recreational drugs. Although still commercially available, barbiturates such as secobarbital, pentobarbital, and amobarbital are no longer routinely recommended for the treatment of insomnia because of their ability to cause dependence, tolerance, and withdrawal. In general, barbiturates lose their efficacy when they are used to treat insomnia on a daily basis for more than two weeks. These drugs also have significant side effects when taken in large doses and can cause respiratory failure and death. Newer and safer medicines are now available for the treatment of insomnia.
Description
The therapeutic effects of barbiturates as a class of drugs are all related to their ability to depress the central nervous system, producing sedation. At high enough doses and with certain preparations, they can induce sleep. All barbiturates also have anticonvulsant properties although phenobarbital is the preferred barbiturate to treat epilepsy because it can produce anticonvulsant effects at levels low enough not to cause extreme sedation or sleep.
Recommended dosage
The typical dose of phenobarbital for use as an anticonvulsant in adults is 60-250 mg per day. When a series of serious seizures known as status epilepticus occurs, adults are usually first given 300-800 mg intravenously (directly into the vein) followed by 120-240 mg every 20 minutes up to a maximum of 1,000-2,000 mg. For sedation, adults are given 30-120 mg per day divided into two or three doses. For sedation before surgery, 100-200 mg are given in an intramuscular injection (a shot) about one hour before the surgery.
The typical dose for an anticonvulsant effect for children must be determined by the doctor, but the usual dose ranges from about 0.45 mg to 2.7 mg per pound (or 1 to 6 mg per kg) per day. For anesthesia before surgery in children, 0.45 mg to 1.35 mg per pound (1 mg to 3 mg per kg) of body weight is given about one hour before the surgery.
The typical dose of butalbital, as a component of headache preparations such as Fiorinal or Fioricet, is 50-100 mg administered every four to six hours as needed.
Precautions
Children who are hyperactive should not receive phenobarbital or other barbiturates. Paradoxically, some children become stimulated and hyperactive after receiving barbiturates.
The use of barbiturates in the elderly (over age 65) should be watched closely. Elderly patients must be carefully monitored for confusion, agitation, delirium, and excitement if they take barbiturates. Barbiturates should be avoided in elderly patients who are receiving drugs for other mental disorders such as schizophrenia or depression.
Women should be aware that barbiturate use can make hormonal birth control pills containing estrogen less effective. Women should not use barbiturates during pregnancy unless they are necessary to control seizures. In these cases, they should take the minimum amount required to control the seizures. Barbiturate use by pregnant women has been associated with increased risk of fetal damage, newborn bleeding problems, bleeding during childbirth, and, if occurring in the final three months of gestation, dependency in the newborn with attendant withdrawal effects after birth. One study has found a potential link between barbiturate use during pregnancy and brain tumors in the infant. Women who are breast-feeding should not take barbiturates because these drugs enter the breast milk and may cause serious side effects in the nursing baby.
Long-term barbiturate use should be avoided unless there is a strong medical need, as in the case of epilepsy, because of the potential for addiction, dependence, tolerance, and withdrawal. People should not drive, operate heavy equipment, or perform other hazardous activities requiring mental alertness while taking barbiturates.
Side effects
The most common side effect of barbiturate use is drowsiness. Less common side effects include agitation, confusion, breathing difficulties, abnormally low blood pressure, nausea, vomiting, constipation, lowered body temperature, decreased heart rate, movement difficulty, nightmares, anxiety, nervousness, mental depression, and dizziness. Rare but reported side effects include fever, headache, anemia, allergic reactions, and liver damage.
Interactions
Patients should always tell their doctor and dentist when they are taking barbiturates. Barbiturates should generally not be taken with other drugs used to treat mental disorders. In addition, patients should inform their healthcare providers about any health or medical problems, especially a history or alcohol or drug abuse, problems with anemia, asthma, diabetes, hyperthyroid, or kidney or liver disease, among others.
There are a number of drugs that barbiturates should not be combined with because the barbiturates may increase the rate of breakdown of these drugs, thus reducing their availability to the body. These drugs include oral corticosteroids such as predisolone, methylprednisolone, prednisone, or dexamethasone, estrogen and oral contraceptives, blood-thinning medications such as warfarin (Coumadin), the antibiotic doxycycline (Vibramycin), and anticonvulsants such as phenytoin (Dilantin).
KEY TERMS
Addiction —A compulsive need for, and use of, a habit-forming substance or behavior.
Anticonvulsant —A medication used to control the abnormal electrical activity in the brain that causes seizures.
Corticosteroids —Any one of a number of hormonal steroid compounds that are derived from the adrenal gland.
Delirium —A disturbance of consciousness marked by confusion, difficulty paying attention, delusions, hallucinations, or restlessness.
Dependence —The adaptation of neurons and other physical processes to the use of a drug, followed by withdrawal symptoms when the drug is removed; physiological and/or psychological addiction.
Hyperactivity —Behavior disturbances, usually in children and adolescents, that involve impulsiveness, low levels of concentration, and distractibility.
Intramuscular —An injection that is given into a muscle.
Monoamine oxidase inhibitors (MAOIs) —A group of antidepressant drugs that decrease the activity of monoamine oxidase, a neurotransmitter found in the brain that affects mood.
Status epilepticus —Series of grand mal epileptic seizures that may occur when the patient is asleep or awake and involves diminished consciousness.
Tolerance —Progressive decrease in the effectiveness of a drug with long-term use.
Withdrawal —Symptoms experienced by a person who has become physically dependent on a drug, occurring when the drug use is discontinued.
Barbiturates should not be combined with alcohol because the combination produces additive depressant effects in the central nervous system.
Barbiturates may lower the amount of absorption of the vitamins D and K.
Resources
BOOKS
Consumer Reports Staff. Consumer Reports Complete Drug Reference, 2002 ed. Denver: Micromedex Thomson Healthcare, 2001.
Ellsworth, Allan J., and others. Mosby’s Medical Drug Reference, 2001-2002. St. Louis: Mosby, 2001.
Hardman, Joel G., and Lee E. Limbird, eds. Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 10th ed. New York: McGraw-Hill, 2001.
Mosby’s GenRx Staff. Mosby’s GenRx, 9th ed. St. Louis: Mosby, 1999.
Venes, Donald, and Clayton L. Thomas. Taber’s Cyclopedic Medical Dictionary, 19th ed. Philadelphia: F. A. Davis, 2001.
OTHER
Cooper, Jeffrey S. “Toxicity, Sedative-Hypnotics.” <http://www.emedicine.com/emerg/topic525.htm>.
National Library of Medicine. National Institutes of Health. “Barbiturates, Systemic.” <http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202081.html>.
Mark Mitchell, MD
Emily Jane Willingham, PhD