barbiturate barbiturate barbiturates are a class of depressant drugs that are chemically derived from barbituric acid. they are effective when used medically as anxiolytics, hypnotics, and anticonvulsants, but have physical and psychological addiction potential as well as overdose potential among other possible adverse effects. they have been used recreationally for their anti-anxiety and sedative effects, and are thus controlled in most countries due to the risks associated with such use. barbituric acid, the parent structure of all barbiturates barbiturates have largely been replaced by benzodiazepines and nonbenzodiazepines ("z-drugs") in routine medical practice, particularly in the treatment of anxiety disorders and insomnia, because of the significantly lower risk of overdose, and the lack of an antidote for barbiturate overdose. despite this, barbiturates are still in use for various purposes: in general anesthesia, epilepsy, treatment of acute migraines or cluster headaches, acute tension headaches, euthanasia, capital punishment, and assisted suicide. uses medicine barbiturates, such as phenobarbital, were long used as anxiolytics and hypnotics. intermediate-acting barbiturates reduce time to fall asleep, increase total sleep time, and reduce rem sleep time. today they have been largely replaced by benzodiazepines for these purposes because the latter are less toxic in drug overdose. however, barbiturates are still used as anticonvulsants (e.g., phenobarbital and primidone) and general anesthetics (e.g., sodium thiopental). barbiturates in high doses are used for medical aid in dying, and in combination with a muscle relaxant for euthanasia and for capital punishment by lethal injection. barbiturates are frequently employed as euthanizing agents in small-animal veterinary medicine. interrogation sodium thiopental is an ultra-short-acting barbiturate that is marketed under the name sodium pentothal. it is often mistaken for "truth serum", or sodium amytal, an intermediate-acting barbiturate that is used for sedation and to treat insomnia, but was also used in so-called sodium amytal "interviews" where the person being questioned would be much more likely to provide the truth whilst under the influence of this drug. when dissolved in water, sodium amytal can be swallowed, or it can be administered by intravenous injection. the drug does not itself force people to tell the truth, but is thought to decrease inhibitions and slow creative thinking, making subjects more likely to be caught off guard when questioned, and increasing the possibility of the subject revealing information through emotional outbursts. lying is somewhat more complex than telling the truth, especially under the influence of a sedative-hypnotic drug. the memory-impairing effects and cognitive impairments induced by sodium thiopental are thought to reduce a subject's ability to invent and remember lies. this practice is no longer considered legally admissible in court, owing to findings that subjects undergoing such interrogations may form false memories, putting the reliability of all information obtained through such methods into question. nonetheless, it is still employed in certain circumstances by defense and law enforcement agencies as a "humane" alternative to torture interrogation when the subject is believed to have information critical to the security of the state or agency employing the tactic. chemistry in 1988, the synthesis and binding studies of an artificial receptor binding barbiturates by six complementary hydrogen bonds was published. since this first article, different kind of receptors were designed, as well as different barbiturates and cyanurates, not for their efficiencies as drugs but for applications in supramolecular chemistry, in the conception of materials and molecular devices. the preferred iupac name of the base compound, barbituric acid, is 1,3-diazinane-2,4,6-trione. different barbiturates have different substituents in the basic structure, mainly in position 5 on the ring. in modern chemistry the barbiturates are often presented by its hirshfeld surface representations showning its intermolecular interactions calculated with crystalexplorer program. hirshfeld surface presentation of barbiturate 2018 sodium barbital and barbital have also been used as ph buffers for biological research, e.g., in immuno-electrophoresis or in fixative solutions. classification barbiturates are classified based on the duration of action. examples of each class include: ultra short acting (30 minutes): thiopentone, methohexitone short acting (2 hours): hexobarbitone, cyclobarbitone, pentobarbitone, secobarbitone intermediate acting(3–6 hours): amobarbitone, butabarbitone long acting (6 hours): phenobarbitone indications indications for the use of barbiturates include: seizure neonatal withdrawal syndrome insomnia anxiety inducing anesthesia side effects addiction experts in psychiatry, chemistry, pharmacology, forensic science, epidemiology, and the police and legal services engaged in delphic analysis regarding 20 popular recreational drugs. barbiturates were ranked third in physical harm, fourth in social harm, and fifth in dependence. there are special risks to consider for older adults, and women who are pregnant. 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 placenta to the 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. a rare adverse reaction to barbiturates is stevens–johnson syndrome, which primarily affects the mucous membranes. common side effects nausea hypotension headache drowsiness skin rash serious side effects confusion coma hallucination fainting slow breathing rare side effects agranulocytosis stevens–johnson syndrome liver injury megaloblastic anemia tolerance and dependence main article: barbiturate dependence with regular use, tolerance to the effects of barbiturates develops. research shows tolerance can develop with even one administration of a barbiturate. as with all gabaergic drugs, barbiturate withdrawal produces potentially fatal effects such as seizures, in a manner reminiscent of delirium tremens and benzodiazepine withdrawal although its more direct mechanism of gaba agonism makes barbiturate withdrawal even more severe than that of alcohol or benzodiazepines. it is considered one of the most dangerous withdrawals of any known addictive substance. similarly to benzodiazepines, the longer acting barbiturates produce a less severe withdrawal syndrome than short acting and ultra-short acting barbiturates. withdrawal symptoms are dose-dependent with heavier users being more affected than lower-dose addicts. the pharmacological treatment of barbiturate withdrawal is an extended process often consisting of converting the patient to a long-acting benzodiazepine (i.e. valium), followed by slowly tapering off the benzodiazepine. mental cravings for barbiturates can last for months or years in some cases and counselling/support groups are highly encouraged by addiction specialists. patients should never try to tackle the task of discontinuing barbiturates without consulting a doctor, owing to the high lethality and relatively sudden onset of the withdrawal. attempting to quit "cold turkey" may result in neurological damage due to excitotoxicity, severe physical injuries received during convulsions, and even death resulting from arrhythmias during grande mal seizures, paralleling death caused by delirium tremens. overdose main article: barbiturate overdose some symptoms of an overdose typically include sluggishness, incoordination, difficulty in thinking, slowness of speech, faulty judgement, drowsiness, shallow breathing, staggering, and, in severe cases, coma or death. the lethal dosage of barbiturates varies greatly with tolerance and from one individual to another. the lethal dose is highly variable among different members of the class, with superpotent barbiturates such as pentobarbital being potentially fatal in considerably lower doses than the low-potency barbiturates such as butalbital. even in inpatient settings, 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. tolerance to the anxiolytic and sedative effects of barbiturates tends to develop faster than tolerance to their effects on smooth muscle, respiration, and heart rate, making them generally unsuitable for a long time psychiatric use. tolerance to the anticonvulsant effects tends to correlate more with tolerance to physiological effects, however, meaning that they are still a viable option for long-term epilepsy treatment. barbiturates in overdose with other cns (central nervous system) depressants (e.g. alcohol, opiates, benzodiazepines) are even more dangerous owing 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, leading to exaggerated benzodiazepine effects. (ex. if a benzodiazepine increases the frequency of channel opening by 300%, and a barbiturate increases the duration of their opening by 300%, then the combined effects of the drugs increases the channels' overall function by 900%, not 600%). the longest-acting barbiturates have half-lives of a day or more, and subsequently result in bioaccumulation of the drug in the system. the therapeutic and recreational effects of long-acting barbiturates wear off significantly faster than the drug can be eliminated, allowing the drug to reach toxic concentrations in the blood following repeated administration (even when taken at the therapeutic or prescribed dose) despite the user feeling little or no effects from the plasma-bound concentrations of the drug. users who consume alcohol or other sedatives after the drug's effects have worn off, but before it has cleared the system, may experience a greatly exaggerated effect from the other sedatives which can be incapacitating or even fatal. barbiturates induce a number of hepatic cyp enzymes (most notably cyp2c9, cyp2c19, and cyp3a4), leading to exaggerated effects from many prodrugs and decreased effects from drugs which are metabolized by these enzymes to inactive metabolites. this can result in fatal overdoses from drugs such as codeine, tramadol, and carisoprodol, which become considerably more potent after being metabolized by cyp enzymes. although all known members of the class possess relevant enzyme induction capabilities, the degree of induction overall as well as the impact on each specific enzyme span a broad range, with phenobarbital and secobarbital being the most potent enzyme inducers and butalbital and talbutal being among the weakest enzyme inducers in the class. people who are known to have killed themselves by barbiturate overdose include stefan zweig, charles boyer, ruan lingyu, dalida, jeannine deckers, felix hausdorff, abbie hoffman, phyllis hyman, c. p. ramanujam, george sanders, jean seberg, lupe vélez and the members of heaven's gate cult. others who have died as a result of barbiturate overdose include pier angeli, brian epstein, judy garland, jimi hendrix, marilyn monroe, inger stevens, dinah washington, ellen wilkinson, and alan wilson; in some cases these have been speculated to be suicides as well. those who died of a combination of barbiturates and other drugs include rainer werner fassbinder, dorothy kilgallen, malcolm lowry, edie sedgwick and kenneth williams. dorothy dandridge died of either an overdose or an unrelated embolism. ingeborg bachmann may have died of the consequences of barbiturate withdrawal (she was hospitalized with burns, the doctors treating her not being aware of her barbiturate addiction). contraindications the use of barbiturates is contraindicated in the following conditions: variegate porphyria (because of induction of enzymes needed for porphyria synthesis by barbiturates) status asthmaticus (because of respiratory depression caused by the barbiturates) mechanism of action barbiturates act as positive allosteric modulators and, at higher doses, as agonists of gabaa receptors. gaba is the principal inhibitory neurotransmitter in the mammalian central nervous system (cns). barbiturates bind to the gabaa receptor at multiple homologous transmembrane pockets located at subunit interfaces, which are binding sites 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 gabaergic effect, barbiturates also block ampa and kainate receptors, subtypes of ionotropic glutamate receptor. glutamate is the principal excitatory neurotransmitter in the mammalian cns. taken together, the findings that barbiturates potentiate inhibitory gabaa receptors and inhibit excitatory ampa receptors can explain the superior cns-depressant effects of these agents to alternative gaba potentiating agents such as benzodiazepines and quinazolinones. at higher concentration, they inhibit the ca2+-dependent release of neurotransmitters such as glutamate via an effect on p/q-type voltage-dependent calcium channels. barbiturates produce their pharmacological effects by increasing the duration of chloride ion channel opening at the gabaa receptor (pharmacodynamics: this increases the efficacy of gaba), whereas benzodiazepines increase the frequency of the chloride ion channel opening at the gabaa receptor (pharmacodynamics: this increases the potency of gaba). the direct gating or opening of the chloride ion channel is the reason for the increased toxicity of barbiturates compared to benzodiazepines in overdose. further, barbiturates are relatively non-selective compounds that bind to an entire superfamily of ligand-gated ion channels, of which the gabaa receptor channel is only one of several representatives. this cys-loop receptor superfamily of ion channels includes the neuronal nach receptor channel, the 5-ht3 receptor channel, and the glycine