Anxiolytic and Sedative Hypnotic Drugs

Anxiolytic and Sedative Hypnotic Drugs

• Anxiolytics and sedative hypnotics are classified based on their mechanism of action and selectivity.
• GABA-facilitating medications: Medications such as barbiturates, zolpidem, and benzodiazepines (BZDs) enhance the effect of GABA on GABA receptors, producing a calming effect.
• They work by binding to the γ subunit of the GABAA receptor, which enhances GABA's ability to bind and activate the receptor.

GABA and BZD Receptor Subtypes

• Different subtypes of BZD receptors exist, showing varying affinity and functional effects.
• BZD₁ receptors primarily contain the α₁ subunit and are linked to sedation and hypnotic effects
• BZD₂ receptors primarily contain the α₂ subunit and are associated with anxiolytic effects and muscle relaxation.
• GABAB receptors are located both pre- and post-synaptically, influencing neuronal activity in two ways:
• Presynaptic GABAB receptors reduce the release of excitatory neurotransmitters like glutamate by decreasing calcium influx, leading to neuronal inhibition.
• Postsynaptic GABAB receptors promote neuronal inhibition by increasing potassium outflow, which hyperpolarizes the neuron, making it less likely to fire action potentials.

Non-GABA Mechanism of Action

• Other medications with anxiolytic and sedative hypnotic effects work through different mechanisms:
• Buspirone functions as a partial agonist of the 5HT1A receptor, resulting in anxiolytic action.
• Melatonin acts as an agonist for MT1 and MT2 receptors, influencing sleep patterns.
• Antidepressants can have anxiolytic effects, although their primary function is to treat depressive disorders.
• Antihistamines often possess sedative properties and are typically available over the counter (OTC).
• Beta blockers can reduce anxiety by decreasing the physical symptoms of anxiety, such as heart rate and blood pressure.
• Clonidine, an α2 agonist, has both anxiolytic and sedative effects by reducing sympathetic nervous system activity.

Selectivity of Anxiolytic and Sedative Hypnotic Effects

• Non-selective drugs possess both anxiolytic and sedative hypnotic effects and are classified as BZDs and barbiturates.
• Selective drugs are targeted toward specific effects:
• Selective hypnotics include zolpidem and ramelteon, aiming to improve sleep quality.
• Selective anxiolytics include buspirone, focusing on reducing anxiety symptoms.

This quiz explores the classification and mechanisms of anxiolytic and sedative hypnotic drugs, focusing on GABA-facilitating medications like benzodiazepines and barbiturates. It examines the various BZD receptor subtypes and their functional effects on sedation and anxiety relief.