The IUPAC systematic name is 5-ethyl-5-phenyl-2,4,6(1H,3H,5H)-pyrimidinetrione. It is also referred to as 5-ethyl-5-phenylbarbituric acid.Molecular formula: Ctop of page Barbiturates are a group of central nervous system depressants which produce effects ranging from mild sedation to general anaesthesia.
The parent compound barbituric acid was first synthesised in 1864 but the first pharmacologically active agent, barbital, was not produced until 1881 and introduced to medicine in 1904.
The most widely used compound, phenobarbital, was synthesised in 1911 and first used clinically the following year.
This may involve impairment of judgement and fine motor skills (e.g.
driving, operating machinery, etc) for up to 22 hours.
Some individuals are reported to have consumed between 1.5 and 2.5 g per day in order to maintain a state of intoxication resembling that caused by alcohol.
A residual central nervous system depression may occur the day following a hypnotic dose.
The lethal dose varies from 2–3 g for amobarbital and pentobarbital to 6–10 g for phenobarbital.
Lethal overdoses are associated with plasma levels of 60 mg/L of phenobarbital but only 10 mg/L of short-acting compounds such as amobarbital and pentobarbital.
Depending on how quickly they act and how long their effects last, they can be classified as ultra-short-, short-, intermediate-, and long-acting. phenobarbital, have selective anti-convulsant activity which makes them useful in epilepsy.
Barbiturates act by enhancing the action of GABA through binding to a site on the GABA receptor/chloride channel, a property they share with benzodiazepines; however, the binding sites of the two drug types differ and as a result, the action of barbiturates is less specific. The resulting risk of overdose means that their use as sedative/hypnotic agents is no longer recommended.
Barbiturates are synthetic substances manufactured as pharmaceutical products.