Barbiturates

 

(bärbĭch'ərāt') , any one of a group of drugs that act as depressants on the central nervous system. High doses depress both nerve and muscle activity and inhibit oxygen consumption in the tissues. In low doses barbiturates act as sedatives, i.e., they have a tranquilizing effect; increased doses have a hypnotic or sleep-inducing effect; still larger doses have anticonvulsant and anesthetic activity. The mechanism of action on the central nervous system is not known. The barbiturates are all derivatives of barbituric acid, which was first prepared in 1864 by the German organic chemist Adolf von Baeyer.

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 Barbiturate addicts must be withdrawn from the drug gradually to avoid severe withdrawal symptoms such as convulsions.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.

Bibliography

See publications of the Drugs & Crime Data Center and Clearinghouse, the Bureau of Justice Statistics Clearinghouse, and the National Clearinghouse for Alcohol and Drug Information.

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. Some are also used as anticonvulsants.

Barbiturates are derivatives of barbituric acid.

History

Barbituric acid was first synthesised on December 4, 1864, by German researcher Adolf von Baeyer. This was done by condensing urea (an animal waste product) with diethyl malonate (an ester derived from the acid of apples). There are several stories about how the substance got its name. The most likely story is that von Baeyer and his colleagues went to celebrate their discovery in a tavern where the town's artillery garrison were also celebrating the day of Saint Barbara — the patron saint of artillerists. An artillery officer is said to have christened the new substance by amalgamating Barbara with urea. [1]

Barbituric acid itself is not pharmacologically active, but chemists immediately began making a great variety of derivatives for potential use as drugs. 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. [2]

In 1912, Bayer introduced another barbituric acid derivative, Phenobarbital, under the trade name Luminal, as a sedative-hypnotic.

In the 1950s and 1960s, reports began to be published about side effects and dependence related to barbiturates.

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 amobarbital (schedule III), butalbital (III), cyclobarbital (III), pentobarbital (III), allobarbital (IV), methylphenobarbital (IV), phenobarbital (IV), secobarbital (IV), and vinylbital (IV) as scheduled substances.

Table of Barbiturates

Barbiturates

Short Name	R1	R5	R5	Full Name
Allobarbital	H	CH2CH1CH2	CH2CH1CH2	5,5-diallylbarbiturate
Amobarbital	H	CH2CH3	CH2CH2 CH(CH3)2	5-ethyl-5-isopentyl-babiturate
Aprobarbital	H	CH2CH1CH2	CH(CH3)2	5-allyl-5-isopropyl-barbiturate
Alphenal	H	CH2CH1CH2	C6H5	5-allyl-5-phenyl-barbiturate
Barbexaclone	H	CH2CH3	C6H5	5-ethyl-5-phenyl-barbiturate
Barbital	H	CH2CH3	CH2CH3	5,5-diethylbarbiturate
Brallobarbital	H	CH2CH1CH2	CH2CBr1CH2	5-allyl-5-(2-bromo-allyl)-barbiturate
Phenobarbital	H	CH2CH3	C6H5	5-phenyl-5-ethylbarbiturate

Mechanism of action

The principal mechanism of action of barbiturates is believed to be their affinity for the GABA_A receptor. GABA is the principal inhibitory neurotransmitter in the mammalian Central Nervous System (CNS). Barbiturates bind to the GABA_A receptor at a binding site distinct from GABA itself and also distinct from the benzodiazepine binding site. Like benzodiazepines, barbiturates potentiate the effect of GABA at this receptor. In addition to this GABA-ergic effect, barbiturates also block the AMPA receptor, a subtype of glutamate receptor. Glutamate is the principal excitatory neurotransmitter in the mammalian CNS. Taken together, the findings that barbiturates potentiate inhibitory GABA_A receptors and inhibit excitatory AMPA receptors can explain the CNS-depressant effects of these agents.^[1]

Therapeutic use

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 abuse and less danger of lethal overdose. Today, fewer than 10 percent of all sedative/hypnotic prescriptions in the United States are for barbiturates. ^{[citation needed]}

Barbiturates are still widely used in surgical anesthesia, especially to induce anesthesia.

Phenobarbital is used for as an anticonvulsant for people suffering from seizure disorders such as febrile seizures, tonic-clonic seizures, status epilepticus, and eclampsia.^[2]

Potential for addiction

Barbiturates are habit forming and lead to physical withdrawal symptoms. These can include tremors, anxiety, weakness, restlessness, nausea and vomiting, delirium, tonic-clonic or grand mal seizures, and cardiac arrest. Death can result from seizures or cardiac arrest.

Effects on the body

Barbiturates are classified as ultrashort-, short-, intermediate-, and long-acting, depending on how quickly they act and how long their effects last. 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.

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.

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. Long-acting barbiturates take effect within one to two hours and last 12 hours or longer.

Similarity to alcohol

Recreational users report that a barbiturate high makes them feel "relaxed, sociable, and good-humored", according to an Independent article. Users typically describe feelings of decreased anxiety, a loss of inhibitions, and an increased sense of confidence. Physical effects include slowed breathing and a lowering of both blood pressure and heart rate.

Like alcohol, barbiturates are intoxicating. During the stage after mild intoxication, the user's speech may be slurred and a loss of coordination may become noticeable. Stumbling and staggering are common. Other symptoms include shallow breathing, fatigue, frequent yawning, and irritability.

When taken in high doses, barbiturates can cause serious side effects, including "unpredictable emotional reactions and mental confusion", noted the Independent. Judgment becomes severely impaired and the user may experience mood swings.

The mental effects of barbiturates generally depend on the amount of the drug taken and the strength of the dosage. Generally, a person falls asleep when taking a prescribed dosage at bedtime. But barbiturates remain in the system for a long time. "At normal doses", explained Cynthia Kuhn and her coauthors in Buzzed: The Straight Facts About the Most Used and Abused Drugs from Alcohol to Ecstasy, "the major concern is that they can have sedative effects that outlast their sleep-inducing properties. Driving, flying an airplane, or other activities requiring muscle coordination can be impaired for up to a day after a single dose." Some barbiturates can be detected in a user's urine sample days or even weeks after the drug was consumed.

Truth serum

Thiopental is a barbiturate that is marketed under the name Sodium Pentothal, but it is probably best known as "truth serum". When dissolved in water, it can be swallowed or administered by intravenous injection. In large doses, it is one of three drugs used in the United States to execute prisoners on death row. In lower doses, it is sometimes used as a truth serum.

Drug experts claim that truth serum does not force people to tell the truth. It merely decreases their inhibitions, making them more likely to be "caught off guard" when questioned by authorities. People being questioned may slip up and expose a lie or give more information on a subject or event than they intended.

Dependence, tolerance, and overdose

Barbiturate use can lead to both psychological and physical dependence. Psychological addiction can occur quickly. Signs of drug dependence include relying on a drug regularly for a desired effect. The addicted abuser believes he or she must take a barbiturate to sleep, relax, or just get through the day. Continued use of barbiturates leads to physical dependence.

As people develop a tolerance for barbiturates, they may need more of the drug or a higher dosage to get the desired effect. This can lead to an overdose, which results when a person takes a larger-than-prescribed dose of a drug. "People who get in the habit of taking sleeping pills every night to fall sleep", noted Andrew Weil and Winifred Rosen in From Chocolate to Morphine, "might start out with one a night, progress to two, then graduate to four to get the same effect. One night the dose they need to fall asleep might also be the dose that stops their breathing." Generally, barbiturate overdoses "occur because the effective dose of the drug is not too far away from the lethal dose", explained Dr. Eric H. Chudler on the Neuroscience for Kids Web site.

Symptoms of an overdose typically include severe weakness, confusion, shortness of breath, extreme drowsiness, an unusually slow heartbeat, and darting eye movements. The amount of a fatal dosage of barbiturate varies from one individual to another. However, the lethal dose is usually ten to fifteen times as large as a usual dose. An overdose affects the heart and the respiratory system. The user then falls into a coma and dies.

Clayton pointed out that barbiturates "can have a 'multiplying' effect when taken with other depressants. For example, if someone drinks alcohol and takes a barbiturate, the effect may be ten times stronger than either one taken separately." According to Weil, "many people have died because they were ignorant of this fact".

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 use

Barbiturates were very popular in the first half of the 20th century. In moderate amounts, these drugs produce a state of intoxication that is remarkably similar to alcohol intoxication. Symptoms include slurred speech, loss of motor coordination, and impaired judgment. Depending on the dose, frequency, and duration of use, one can rapidly develop tolerance, physical dependence, and psychological dependence on barbiturates. With the development of tolerance, the margin of safety between the effective dose and the lethal dose becomes very narrow. That is, in order to obtain the same level of intoxication, the tolerant abuser may raise his or her dose to a level that may result in coma or death. Although many individuals have taken barbiturates therapeutically without harm, concern about the addiction potential of barbiturates and the ever-increasing number of fatalities associated with them led to the development of alternative medications, namely benzodiazepines.

Other non-therapeutical use

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.

Famous users

• Abbie Hoffman - anarchist in the 1960s, committed suicide
• Ryūnosuke Akutagawa - the renowned Japanese writer who wrote Rashomon, committed suicide by overdosing on barbiturates on July 24, 1927.
• Adolf Hitler - Speculated addiction to methamphetamine and Cocaine, used barbiturates to sleep.
• Judy Garland died from an accidental barbiturate overdose
• Gertrude Hullett, a patient of the suspected British serial killer John Bodkin Adams, died from an overdose in 1956. He was charged with her murder but controversially acquitted.
• Marilyn Monroe also died with barbiturates present in her bloodstream, however the amount of barbiturates for an overdose was not present.
• George Sanders, Kenneth Williams (although an open verdict was recorded) and Jean Seberg.
• Michael Rabin, one of the most prodigious violinists America has ever had, became dependent on barbiturates and his death was partially linked to abuse of these drugs.
• Jimi Hendrix's death was a combination of barbiturate overdose and vomit inhalation (pulmonary aspiration).
• Tim Buckley, singer-songwriter and father of Jeff Buckley, died from an accidental overdose of heroin, alcohol, and barbiturates.
• Ruan Lingyu committed suicide by overdosing on barbiturates on March 8, 1935.
• Johnny Cash abused barbiturates during the height of his career.
• Elvis Presley used barbiturates in the last years of his life, but whether this contributed to his death is disputed.
• Margaux Hemingway died from an overdose of phenobarbital.
• Dorothy Kilgallen died in 1965 of an alcohol and Seconal overdose. It is unclear whether the overdose was accidental or murder.
• Dalida committed suicide in 1987 by taking a leathel dose of barbiturates
• Diane Arbus committed suicide in 1971 by taking barbiturates and slitting open her wrists.
• Pier Angeli died in 1971 of an overdose of barbiturates.
• Inger Stevens committed suicide in 1970 of an overdose of barbiturates at the age of 36.
• Donald Sinclair Better known as "Siegfred Farnon" in James Herriot's collective books "All Things Great and Small". He committed suicide in 1995.
• Michael Reeves English film director who died accidentally of a barbiturate overdose.
• Jean Seberg Actress died from a barbiturate overdose in Paris, 1979.
• Edie Sedgwick The actress and model was found dead in bed on November 16th 1971 due to 'acute barbiturate intoxication' at the age of 28.
• Kenneth Williams Comedy actor in twenty-six Carry On Films.
• Aimee Semple McPherson American female evangelical preacher died (accidental overdose)
• George Dyer Francis Bacon's partner, suicide
• William S. Burroughs American author of "Junky" mentions taking "goof balls" a common 50's term.

External links

• U.S. Drug Enforcement Administration Source for some public domain text used on this page.
• Erowid.org - Barbiturates
• Chemcases profile
• Barbiturate history and chemistry

References

Barbiturates (N01AF, N03AA, N05CA)

Allobarbital • Amobarbital • Aprobarbital • Alphenal • Barbexaclone • Barbital • Brallobarbital • Butabarbital • Butalbital • Butobarbital • Butallylonal • Crotylbarbital • Cyclobarbital • Cyclopal • Ethallobarbital • Febarbamate • Hexethal • Heptabarbital • Hexobarbital • Mephobarbital • Metharbital • Methohexital • Methylphenobarbital • Narcobarbital • Pentobarbital • Phenobarbital • Probarbital • Propallylonal • Proxibarbal • Proxibarbital • Reposal • Secbutabarbital • Secobarbital • Talbutal • Thialbarbital • Thiamylal • Thiobarbital • Thiobutabarbital • Thiopental • Valofane • Vinbarbital • Vinylbital

Donate to Wikimedia