Master Barbiturates with Picmonic for Medicine

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Phenobarbital (Barbiturates)

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Benzodiazepines Overview

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Nonbenzodiazepine Hypnotics

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Short-acting Benzodiazepines

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Succinylcholine

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Barbiturates

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Barbiturates are medications with a wide range of use and side effects. They can be remembered by having "barb" in their names, such as phenobarbital and pentobarbital. They are indicated for seizure treatment, and are effective against simple and complex partial seizures, as well as generalized tonic-clonic seizures. The barbiturate thiopental is a very fast acting medication used for anesthesia induction. These drugs work by potentiating GABA_A, leading to increased chloride channel opening duration. This increased chloride channel opening duration leads to decreased neuronal firing. It should be remembered that barbiturates increase the duration of chloride channel opening, whereas benzodiazepines increase the frequency of chloride channel opening. Side effects of this class of drug include sedation and grogginess. A severe side effect is respiratory and cardiac depression, which can progress to respiratory arrest and low blood pressure in patients who overdose or recreationally use barbiturates. CNS depression may also occur, and abuse with ethanol can cause additive adverse effects, as barbiturates and ethanol both act on GABA_A receptors. Finally, these drugs induce the cytochrome P450 enzyme complex and may affect the metabolism of other medications.

9 KEY FACTS

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 GABA_A 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 GABA_A, 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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