Barbiturates can be remembered for having "barb" in their names. Common examples are phenobarbital, pentobarbital and secobarbital, with the anesthetic thiopental being the exception.
Barbiturates such as phenobarbital are indicated for seizures. They are used to treat epilepsy and are effective against simple and complex partial seizures, as well as generalized tonic-clonic seizures.
Ultra-short acting barbiturates can be used for anesthesia induction, exemplified by thiopental. Thiopental is administered intravenously and has been nicknamed the "truth serum" as it may influence patients to divulge sensitive information.
Barbiturates work by allosterically modulating GABAA receptors. This leads to increased efficacy of GABA, causing an increase in the duration of Cl- channel opening. In contrast to these drugs, benzodiazepines increase the frequency of Cl- channel opening.
"Barb opens her chloride channel for a long duration, nice and slow"
By increasing Cl- channel opening duration, neuronal firing is decreased.
Barbiturates, in the past, were used to treat insomnia and anxiety. They are no longer for these purposes as patients were left sedated and groggy. Patients often complain of feeling "hungover."
Barbiturates often mimic ethanol, and can lead to severe respiratory and cardiovascular depression. This is often displayed as respiratory arrest and low blood pressure in patients who abuse these drugs.
This side effect occurs with overdose and can also be seen with concurrent ethanol use. Barbiturates bind to GABAA, as does ethanol, explaining their additive effects. Patients can display ataxia, dizziness, impaired judgement and can progress to death.
These medications induce cytochrome P450. P450 enzymes assist in removing many drugs from the blood stream. When these enzymes are increased, the clearance of such drugs from the blood is also increased. Therefore, barbiturates can shorten the effects of other administered drugs, making them less effective.
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