Methohexital is an ultrashort-acting barbiturate widely used in dentistry because of its rapid onset, predictable effects, and short duration of action. It was marked under the name brevital sodium for the intravenous anaesthesia. It has also been commonly used to induce deep sedation. Like other barbiturates, methohexital exerts its effects through the gamma-aminobutyric acid (GABA) receptor complex. By binding to its own receptor on the complex, methohexital augments the inhibitory effect of GABA on neurons and additionally can exert a similar effect independent of GABA.

Primidone is an anticonvulsant of the barbiturate class. It was introduced in 1954 under the brand name Mysoline by Wyeth in the United States. Mysoline, used alone or concomitantly with other anticonvulsants, is indicated in the control of grand mal, psychomotor, and focal epileptic seizures. It may control grand mal seizures refractory to other anticonvulsant therapy. Mysoline raises electro- or chemoshock seizure thresholds or alters seizure patterns in experimental animals. The mechanism(s) of primidone’s antiepileptic action is not known. Primidone per se has anticonvulsant activity, as do its two metabolites, phenobarbital and phenylethylmalonamide (PEMA). In addition to its anticonvulsant activity, PEMA potentiates the anticonvulsant activity of phenobarbital in experimental animals. Primidone itself doesn’t act on GABA-A receptors. It is active metabolite - phenobarbital primary acts via modulation of GABA -A receptors. The most frequently occurring early side effects are ataxia and vertigo. These tend to disappear with continued therapy, or with reduction of initial dosage. Occasionally, the following have been reported: nausea, anorexia, vomiting, fatigue, hyperirritability, emotional disturbances, sexual impotency, diplopia, nystagmus, drowsiness, and morbilliform skin eruptions.Granulocytopenia, agranulocytosis, and red-cell hypoplasia and aplasia, have been reported rarely. These and, occasionally, other persistant or severe side effects may necessitate withdrawal of the drug. Megaloblastic anemia may occur as a rare idiosyncrasy to Mysoline and to other anticonvulsants. The anemia responds to folic acid without necessity of discontinuing medication.

Butalbital, 5-allyl-5-isobutylbarbituric acid, is a barbiturate with an intermediate duration of action. The different combinations with butalbital is approved. One of them is fioricet with codeine (butalbital, ccetaminophen, caffeine, and codeine phosphate) which is indicated for the relief of the symptom complex of tension (or muscle contraction) headache. Evidence supporting the efficacy and safety of fioricet with codeine in the treatment of multiple recurrent headaches is unavailable. Butalbital is well absorbed from the gastrointestinal tract and is expected to distribute to most tissues in the body. This compound in general may appear in breast milk and readily cross the placental barrier. Monoamine oxidase (MAO) inhibitors may enhance the CNS effects. The mechanism of action for butalbital is proposed the following: this compound binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged.

Pentobarbital belongs to the class of a short-acting barbiturate is used as sedatives, hypnotics, for the short-term treatment of insomnia, since they appear to lose their effectiveness for sleep induction and sleep maintenance after 2 weeks; preanesthetics and anticonvulsant, in anesthetic doses, in the emergency control of certain acute convulsive episodes, e.g., those associated with status epilepticus, cholera, eclampsia, meningitis, tetanus, and toxic reactions to strychnine or local anesthetics. Pentobarbital binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged. All of these effects are associated with marked decreases in GABA-sensitive neuronal calcium conductance (gCa). The net result of barbiturate action is acute potentiation of inhibitory GABAergic tone. Barbiturates also act through potent (if less well characterized) and direct inhibition of excitatory AMPA-type glutamate receptors, resulting in a profound suppression of glutamatergic neurotransmission.

Phenobarbital is a barbiturate derivative used to treat insomnia and anxiety, seizures, hyperbilirubinemia in neonates and cholestasis. Phenobarbital promotes binding to inhibitory gamma-aminobutyric acid subtype receptors, and modulates chloride currents through receptor channels.

Eterobarb (Antilon) is a barbiturate derivative. It is an effective anticonvulsant as demonstrated in animal and clinical studies. Eterobarb possesses a unique and clinically intriguing feature-at therapeutically effective blood levels, the hypnotic side effects usually associated with barbiturates appear absent. Though effective against both electrically and chemically induced seizures in mice and rats, virtually no hypnotic effects were noted except at lethal doses. Double-blind cross-over studies have confirmed the anticonvulsant efficacy of eterobarb and several phase II and phase Ill studies show eterobarb to be an effective anticonvulsant with less hypnotic activity when compared with phenobarbital. Eterobarb had been NDA filed for the treatment of epilepsy in the US, UK, Switzerland and Canada. However, this research has been discontinued. The compound was originated by Colgate Palmolive, then licensed to MacroChem.

THIALBARBITAL is a barbiturate derivative with sedative effects. Barbiturates have hypnotic properties and are used as active moiety on central nervous system. Thialbarbital was synthesized in the 1960s. It was used primarily as a surgical anesthesia. Thialbarbital causes marked depression of the activity of the reticular formation and only slight depression of cortical activity. Thialbarbital is short acting and has less of a tendency to induce respiratory depression than other barbiturate derivatives such as pentobarbital.

Nealbarbital (Censedal) is a barbiturate derivative, an effective sedative with only slight hypnotic action.

Benzobarbital (under the brand name Benzona), a barbiturate derivative developed in Russia that is used to treat convulsive forms of epilepsy, newborn hemolytic disease, and insomnia.

Phetharbital (Pyrictal), a barbiturate with virtually no hypnotic side effects, was originally introduced for the management of epilepsy and has since been shown to have powerful hepatic enzyme-inducing properties. In preliminary clinical studies, phetharbital was found to be effective against febrile seizures, minor myoclonic seizures and in petit mal. Phetharbital is relatively ineffective in the control of the tonic extensor seizure pattern and would not be expected to modify grand mal tonic seizures. Chronic administration of phetharbital causes an increased excretion of 6 beta-hydroxycortisol in human urine. This increase in 6 beta-hydroxycortisol excretion is not accompanied by an increase in the 17-hydroxycorticosteroids levels in urine, indicating that an increased adrenal output of cortisol is not responsible for the increased urinary levels of 6 beta hydroxycortisol. Phetharbital was also effective in the rare severe unconjugated hyperbilirubinemia of the Crigler-Najjar syndrome.