Barbiturates

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Barbiturates are a group of drugs that act as depressants on the central nervous system (the brain and spinal cord). They are derived from barbituric acid, a chemical discovered in 1863. Scientists looking for a drug to treat anxiety and nervousness that would not produce dependence (as do codeine and morphine) changed the structure of barbituric acid and synthesized barbital. Barbital, a depressant, was introduced as a medicine in 1903, followed by phenobarbital in 1913.

Since that time, more than 2,000 similar chemicals have been synthesized, but only about 50 of these have been sold as medicines. As more people took the drugs, the side effects of barbiturates became apparent. An overdose can result in respiratory depression (slowing or stopping normal breathing processes), which can be fatal. Doctors also realized that the barbiturates can be abused. People can become dependent on them, and a serious withdrawal syndrome can occur when a person abruptly stops taking the drugs. In the 1960s, the introduction of the benzodiazepines, a safer class of hypnotic drugs (drugs that bring on sleep), replaced barbiturates for certain prescribed uses.

Barbiturates are taken by mouth. Injecting the drug is a rare practice among barbiturate abusers. Barbiturates come in brightly colored capsules, with street names such as blue birds, blue clouds, yellow jackets, red devils, sleepers, pink ladies, and Christmas trees. The term "goofball" refers to barbiturates in general. The accompanying table lists the common barbiturates and their trade names.

CLASSIFICATION OF BARBITURATES
		Drug Class and Generic Names	Trade Names
		Ultrashort-Acting:
		methohexital sodium	Brevital
thiamylal sodium	Surital
thiopental sodium	Pentothal
Short-Acting:
butalbital
hexobarbital	Sombulex
pentobarbital	Nembutal
secobarbital	Seconal
Intermediate-Acting:
amobarbital	Amytal
aprobarbital	Alurate
butabarbital	Butisol
talbutal	Lotusate
Long-Acting:
phenobarbital	Luminal
mephorbarbital	Mebaral
SOURCE: Rall, 1990; Csáky, 1979.

Barbiturates work by affecting a neurotransmitter (brain chemical) that normally acts as a brake on the electrical activity of the brain. Barbiturates enhance, or increase, the braking effects of this chemical, causing sedation. The area in the brain called the reticular activating system is responsible for keeping people awake. It is the first area to be affected by the barbiturates. This is why an individual becomes tired and falls asleep after taking a barbiturate.

The various barbiturates differ mainly in how quickly they take effect and how long they keep acting. They can range from ultrashort-acting (taking effect within seconds and lasting a few minutes) to long-acting (taking effect in an hour and lasting six to twelve hours).

The effects of barbiturates range from mild sedation (decreased responsiveness), to hypnosis (sleep), to anesthesia (loss of sensation). A small dose will produce sedation and relieve anxiety and tension; a somewhat larger dose taken in a quiet setting will usually produce sleep; and an even larger dose will produce unconsciousness. How barbiturates affect an individual depends on the user's previous drug experience and the circumstances in which the drug is taken. For example, a dose taken at bedtime may produce sleep, whereas the same dose taken during the daytime may produce a feeling of euphoria and interfere with normal motor skills. This is similar in many ways to the effects of alcohol.

Barbiturate-induced sleep resembles normal sleep in many ways, but there are a few important differences. Barbiturates reduce the amount of time spent in rapid eye movement or REM sleep—a very important phase of sleep. Prolonged use of barbiturates causes restlessness during the late stages of sleep. Since the barbiturates remain in the body for some time after a person awakens, a feeling of drowsiness can interfere with judgment and moods for some time after the sedative effects have disappeared.

Doctors sometimes prescribe barbiturates to promote sleep in patients with insomnia. The general use of barbiturates as sleeping pills has decreased significantly, however, since they have been replaced by the safer benzodiazepines. Phenobarbital and butabarbital are still available as prescription medications used to treat inflammatory disorders. The ultrashort-acting barbiturates (such as thiopental) are given intravenously to induce anesthesia because of how easily and quickly they take effect.

Some barbiturates reduce seizures and so have been used to treat some forms of epilepsy. Phenobarbital is often used in hospital emergency rooms to treat convulsions such as those that develop during tetanus, cerebral hemorrhage (bleeding in the brain), and poisoning by convulsant drugs. The benzodiazepines are, however, gradually replacing the barbiturates in this setting as well.

A person who takes barbiturates repeatedly develops tolerance to the drug's effects. This means that more and more drug is needed to achieve the effect the person got from the initial dose. However, tolerance does not develop equally in all of barbiturates' effects. For example, users do not develop tolerance to respiratory depression. Barbiturates reduce the drive to breathe and the processes necessary for maintaining a normal breathing rhythm. A person who takes a barbiturate for its sedative effect develops tolerance to that effect. But the dose now required to achieve that sedative effect has a toxiceffect on the respiratory system. Thus the higher dose can cause death by completely stopping breathing.

If tolerance develops and the amount of drug taken continues to increase, then physical dependence can develop. If the drug is suddenly stopped, withdrawal signs appear. In the case of barbiturates, mild signs of withdrawal include:

• fear
• insomnia
• excitability
• mild tremors (shaking)
• loss of appetite

If the dose was very high, more severe signs of withdrawal can occur, including:

• weakness
• vomiting
• decrease in blood pressure regulatory mechanisms (so that a person might pass out when rising from a lying position)
• increased pulse and respiratory rates
• epileptic seizures or convulsions
• delirium with fever, disorientation, and hallucinations

Unlike withdrawal from the opioids (such as morphine and heroin), withdrawal from central nervous system depressants such as barbiturates can be life threatening. The proper treatment of a barbiturate-dependent individual always includes a slow reduction in the dose to avoid the dangers of rapid detoxification.

Many people who take barbiturates with a doctor's prescription to treat insomnia become dependent to some degree. Some of these individuals abuse the drug by taking increasingly larger doses to get the euphoric effect rather than to get the intended effect of sleepiness. In need of ever more drug, the person may obtain prescriptions from a number of doctors and take them to a number of pharmacists, or may buy the drug from illegal dealers. The person may abuse the drug daily or during binges that last from a day to many weeks at a time. This pattern of using barbiturates for the euphoric effect is more common among people who begin by buying barbiturates from illicit sources than among those who begin by seeking help for insomnia.

People who are dependent on a particular drug often take barbiturates to boost the first drug's effects. Alcohol and heroin are alsocommonly taken together in this way. Since barbiturates are "downers," people also take them to counteract the unwanted overstimulation that stimulant drugs produce. Abusers of stimulants such as cocaine or amphetamines ("uppers") use barbiturates to come down from the continued high. Also, barbiturates are used to ward off the early signs of withdrawal from alcohol.

Doctors must carefully control treatment for barbiturate dependence because of the potential dangers, such as seizures. Withdrawal must be closely supervised. Doctors give the patient phenobarbital or the benzodiazepines—chlordiazepoxide and diazepam—in gradually decreasing doses to reduce the severity of withdrawal symptoms.

Addiction: Concepts and Definitions; Benzodiazepines.

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