Barbiturates

Barbiturates are drugs that act as central nervous system depressants, and by virtue of this they produce a wide spectrum of effects, from mild sedation to anesthesia. They are also effective as anxiolytics, hypnotics and as anticonvulsants. They have addiction potential, both physical and psychological. Barbiturates have now largely been replaced by benzodiazepines mainly because benzodiazepines are significantly less dangerous in overdose. Barbiturates are derivatives of barbituric acid.

Therapeutic uses

Barbiturates like pentobarbital and phenobarbital were long used as anxiolytics and hypnotics. Today benzodiazepines have largely supplanted them for these purposes, because benzodiazepines have less potential for lethal overdoses.

Barbiturates are classified as ultrashort-, short-, intermediate-, and long-acting, depending on how quickly they act and how long their effects last. Barbiturates are still widely used in surgical anesthesia, especially to induce anesthesia, though their use during induction of anesthesia has largely been supplanted by Propofol. Ultrashort barbiturates such as thiopental (Pentothal) produce unconsciousness within about a minute of intravenous (IV) injection. These drugs are used to prepare patients for surgery; other general anesthetics like nitrous oxide are then used to keep the patient from waking up before the surgery is complete. Because Pentothal and other ultrashort-acting barbiturates are typically used in hospital settings, they are not very likely to be abused, noted the DEA.

Phenobarbital is used as an anticonvulsant for people suffering from seizure disorders such as febrile seizures, tonic-clonic seizures, status epilepticus, and eclampsia.

Long-acting barbiturates such as phenobarbital (Luminal) and mephobarbital (Mebaral) are prescribed for two main reasons. When taken at bedtime, they help treat insomnia. When taken during the day, they have sedative effects that can aid in the treatment of tension and anxiety. These same effects have been found helpful in the treatment of convulsive conditions like epilepsy. Phenobarbital has also been used in the treatment of delirium tremens during alcohol detoxification, although benzodiazepines have a more favorable safety profile and are more often used. Long-acting barbiturates take effect within one to two hours and last 12 hours or longer.

Other non-therapeutic uses

Barbiturates in high doses are used for physician-assisted suicide (PAS), and in combination with a muscle relaxant for euthanasia and for capital punishment by lethal injection. Thiopental, an ultra-short acting barbiturate that is marketed under the name Sodium Pentothal, is sometimes used as a "truth serum". When dissolved in water, it can be swallowed or administered by intravenous injection. The drug does not itself force people to tell the truth, but is thought to decrease inhibitions, making subjects more likely to be caught off guard when questioned.

Tolerance, dependence and overdose

Older adults and pregnant women should consider the risks associated with barbiturate use. When a person ages, the body becomes less able to rid itself of barbiturates. As a result, people over the age of sixty-five are at higher risk of experiencing the harmful effects of barbiturates, including drug dependence and accidental overdose. When barbiturates are taken during pregnancy, the drug passes through the mother's bloodstream to her fetus. After the baby is born, it may experience withdrawal symptoms and have trouble breathing. In addition, nursing mothers who take barbiturates may transmit the drug to their babies through breast milk.

Tolerance and dependence

With regular use tolerance to the effects of barbiturates develops. This in turn may lead to a need for increasing doses of the drug to get the original desired pharmacological or therapeutic effect. Barbiturate use can lead to both psychological and physical dependence and the drugs have a high abuse liability. Psychological addiction to barbiturates can develop quickly. The GABAA receptor, one of barbiturates' main sites of action, is thought to play a pivotal role in the development of tolerance to and dependence on barbiturates, as well as the euphoric "high" that results from their abuse. The mechanism by which barbiturate tolerance develops is believed to be different than that of ethanol or benzodiazepines, even though these drugs have been shown to exhibit cross-tolerance with each other.

Overdose

An overdose results when a person takes a larger-than-prescribed dose of a drug. Symptoms of an overdose typically include; sluggishness, incoordination, difficulty in thinking, slowness of speech, faulty judgment, drowsiness or coma, shallow breathing, staggering and in severe cases coma and death. The lethal dosage of barbiturates varies greatly with tolerance and from one individual to another. Even in inpatient settings, however, the development of tolerance is still a problem, as dangerous and unpleasant withdrawal symptoms can result when the drug is stopped after dependence has developed. Barbiturates in overdose with other CNS depressants for example, alcohol, opiates or benzodiazepines is even more dangerous due to additive CNS and respiratory depressant effects. In the case of benzodiazepines not only do they have additive effects, barbiturates also increase the binding affinity of the benzodiazepine binding site thus leading to an exagerated effect of benzodiazepines.

Recreational use

Like ethanol, barbiturates are intoxicating and produce similar effects during intoxication. The symptoms of barbiturate intoxication include respiratory depression, lowered blood pressure, fatigue, fever, unusual excitement, irritability, dizziness, poor concentration, sedation, confusion, impaired coordination, impaired judgment, addiction, and respiratory arrest which may lead to death.

Recreational users report that a barbiturate high gives them feelings of relaxed contentment and euphoria. The main risk of acute barbiturate abuse is respiratory depression. Physical and psychological dependence may also develop with repeated use. Other effects of barbiturate intoxication include drowsiness, lateral and vertical nystagmus, slurred speech and ataxia, decreased anxiety, a loss of inhibitions. Barbiturates are also misused to alleviate the adverse or withdrawal effects of illicit drug misuse.

Drug users tend to prefer short-acting and intermediate-acting barbiturates. The most commonly abused are amobarbital (Amytal), pentobarbital (Nembutal), and secobarbital (Seconal). A combination of amobarbital and secobarbital (called Tuinal) is also highly abused. Short-acting and intermediate-acting barbiturates are usually prescribed as sedatives and sleeping pills. These pills begin acting fifteen to forty minutes after they are swallowed, and their effects last from five to six hours. Veterinarians use pentobarbital to anesthetise animals before surgery; in large doses, it can be used to euthanise animals.

Slang terms for barbiturates include; barbs, bluebirds, blues, downers, goofballs, tooties and yellow jackets.

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