Sedatives and Hypnotics - Definition, Classification & Examples

Sedatives and hypnotics are central nervous system (CNS) depressants that reduce anxiety (anxiolytic effect), induce sedation (calming effect), or promote sleep (hypnotic effect).
The same compound may act as a sedative or hypnotic depending on the dose and pharmacokinetics.

Mechanism (brief)
- Enhance the effect of GABA (gamma-aminobutyric acid) at the GABA-A receptor, increasing the frequency of chloride channel opening, leading to CNS depression.
Examples of Benzodiazepines:
- Chlordiazepoxide
- Diazepam
- Oxazepam
- Chlorazepate
- Lorazepam
- Alprazolam
- Zolpidem (Note: Chemically distinct but acts at benzodiazepine binding site – often grouped with BZDs for pharmacology)

Mechanism (brief)
- Act on GABA-A receptors to prolong the duration of chloride channel opening.
- At higher doses, they can mimic GABA, leading to more profound CNS depression.
Examples of Barbiturates:
- Barbital
- Phenobarbital
- Mephobarbital
- Amobarbital
- Butabarbital
- Pentobarbital
- Secobarbital

Amides & Imides
- Structural similarity to barbiturates.
- Act as CNS depressants.
- Example:
  - Glutethimide
Alcohols & Carbamate Derivatives
- Possess sedative-hypnotic
- Carbamate derivatives act as CNS depressants similar to older sedatives.
- Examples:
  - Meprobamate
  - Ethchlorvynol
Aldehydes & Their Derivatives
- Used for short-term sedation.
- Work by depressing CNS activity, though mechanisms can vary.
- Examples:
  - Triclofos sodium
  - Paraldehyde

Class	Mechanism of Action	Examples	Key Notes / Uses
Benzodiazepines	Enhance GABA-A receptor activity → increase frequency of Cl⁻ channel opening → CNS depression	Chlordiazepoxide, Diazepam, Oxazepam, Chlorazepate, Lorazepam, Alprazolam, Zolpidem*	Anxiolytics, hypnotics, anticonvulsants, muscle relaxants. Zolpidem is non-BZD but binds same site.
Barbiturates	Enhance GABA-A activity → prolong Cl⁻ channel opening; at high doses, mimic GABA → profound CNS depression	Barbital, Phenobarbital, Mephobarbital, Amobarbital, Butabarbital, Pentobarbital, Secobarbital	Less safe than BZDs; used in epilepsy and anesthesia. Risk of dependence, overdose.
Amides & Imides	Structurally similar to barbiturates; act as CNS depressants	Glutethimide	Formerly used as sedative; replaced due to abuse potential and safer alternatives.
Alcohols & Carbamate Derivatives	Depress CNS via uncertain mechanisms; carbamates similar to older sedatives	Meprobamate, Ethchlorvynol	Meprobamate has anxiolytic properties; now rarely used due to safety concerns.
Aldehydes & Derivatives	Depress CNS activity; exact mechanism varies	Triclofos sodium, Paraldehyde	Used for short-term sedation; paraldehyde historically used in seizures and delirium.