The drugs differ widely in the duration of their action, which depends on the rapidity with which they are distributed in body tissues, degraded, and excreted. Ultrashort-acting barbiturates such as thiopental sodium (Pentothal) are often used as general anesthetics. Secobarbital (Seconal) and pentobarbital sodium (Nembutal) are short-acting barbiturates, amobarbital (Amytal) is intermediate in duration of action, and phenobarbital (Luminal) is a long-acting derivative.
Barbiturates are used to relax patients before surgery, as anticonvulsants, and as sleeping pills. They also are commonly abused. Taken regularly, barbiturates can be psychologically and physically addictive (see drug addiction and drug abuse). Barbiturate addicts must be withdrawn from the drug gradually to avoid severe withdrawal symptoms such as convulsions. Overdose can cause coma or death. In the United States the manufacture and distribution of barbiturates were brought under federal control by the 1965 Drug Abuse and Control Act, and they are legally available only by prescription.
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Any of a class of heterocyclic compounds based on the parent structure, uric acid, and used in medicine. They depress the central nervous system, acting particularly on certain parts of the brain, though they tend to depress the functioning of all the body's tissues. Long-acting barbiturates (e.g., barbital and phenobarbital) are used to treat epilepsy. Intermediate ones (e.g., amobarbital) are used to treat insomnia, short-acting ones (e.g., pentobarbital) to overcome difficulty in falling asleep (one aspect of insomnia), and ultra-short-acting ones (e.g., thiopental sodium) to induce unconsciousness in surgical patients before administration of other anesthetics. Prolonged use of barbiturates may lead to addiction. Sudden withdrawal can be fatal; addicts must be weaned from the drug under medical supervision. Overdoses can result in coma and even death; barbiturates are particularly dangerous, even at normal doses, when combined with alcoholic beverages.
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While barbituric acid itself does not have any effect on the central nervous system, to date, chemists have derived over 2,500 compounds that do possess pharmacologically active qualities. The broad class of barbiturates is broken down further and classified according to speed of onset and duration of action. Ultrashort-acting barbiturates are commonly used for anesthesia because their extremely short duration of action allows for greater control. These properties allow doctors to rapidly put a patient "under" in emergency surgery situations. Doctors can also bring a patient out of anesthesia just as quickly should complications arise during surgery. The middle two classes of barbiturates are often combined under the title "short/intermediate-acting." These barbiturates are also employed for anesthetic purposes, and are also sometimes prescribed for anxiety or insomnia. This is not a common practice anymore, however, due to the addiction liability associated with barbiturates; they have been replaced by the benzodiazepines for these purposes. The final class of barbiturates are known as long-acting barbiturates (most notably phenobarbital, which has a half-life of roughly 92 hours). This class of barbiturates is used almost exclusively as anticonvulsants, although on rare occasions they are prescribed for daytime sedation. Barbiturates in this class are not used for insomnia, because due to their extremely long half-life, patients would awake with a residual "hang-over" effect and feel groggy. No substance of medical value was discovered, however, until 1903 when two German chemists working at Bayer, Emil Fischer and Joseph von Mering, discovered that barbital was very effective in putting dogs to sleep. Barbital was then marketed by Bayer under the trade name Veronal. It is said that Von Mering proposed this name because the most peaceful place he knew was the Italian city of Verona.
Barbiturates can in most cases be used as either the free acid or as salts of sodium, calcium, potassium, magnesium, lithium, etc. Codeine- and Dionine-based salts of barbituric acid have been developed. In 1912, Bayer introduced another barbituric acid derivative, phenobarbital, under the trade name Luminal, as a sedative-hypnotic.
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. 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.
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.
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.
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.
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 psychic 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 abusers 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.
In 1970 several barbiturates were designated in the United States as controlled substances with the passage of the American Controlled Substances Act of 1970. Pentobarbital, secobarbital and amobarbital were designated schedule II drugs, butabarbital schedule III, and barbital and phenobarbital schedule IV. In 1971 the Convention on Psychotropic Substances was signed in Vienna. Designed to regulate amphetamines, barbiturates, and other synthetics, the treaty today regulates secobarbital, amobarbital, butalbital, cyclobarbital, and pentobarbital as schedule III, and allobarbital, methylphenobarbital, phenobarbital, and vinylbital as schedule IV scheduled substances.
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Continuous noninvasive monitoring of barbiturate coma in critically ill children using the Bispectral[TM] index monitor.(Research)
Sep 27, 2007; Authors: Sandra A Prins ; Matthijs de Hoog ; Joleen H Blok ; Dick Tibboel (corresponding author) ; Gerhard H Visser...