Zolpidem

Mechanism

Chemical and Commercial Profile

Common trade names: Stilnox, Dalparan, Zolpidem Normon.
Group: Fast-acting imidazopyridine hypnotic (Compound Z).

Mechanism of Action

Unlike classical benzodiazepines that bind diffusely to multiple subunits of the GABAergic receptor, zolpidem shows an extreme selective affinity for the GABA_A receptor containing the α₁ subunit (BZD1-type receptors), located predominantly in the cerebral cortex, the globus pallidus and the cerebellum.

This selectivity gives it powerful sedative and rapid sleep-inducing properties, with minimal muscle-relaxing, anxiolytic or systemic anticonvulsant effects in therapeutic doses.

Pharmacokinetics

Pharmacokinetics

• Absorption: Ultra-rapid after oral intake; 70% bioavailability. C_max in 30-90 minutes. Concomitant intake with fatty foods delays its absorption and reduces the effective plasma peak.
• Metabolism: Hepatic through oxidation by the isoenzymes CYP3A4 (60%), CYP2C9 and CYP1D2, generating three inactive metabolites.
• Excretion: Renal (60%) mainly in the form of inactive metabolites.
• Half-life (t_1/2): Short: 1.5 to 2.5 hours. It ensures its total plasma elimination before the usual 8 hours of sleep have elapsed, preventing the residual effect of a morning hangover.

Indicators and dose

Indications

• Short-term treatment of transient and chronic sleep insomnia in adults, when it seriously alters the quality of daily life.

Dosage and Settings

• Adults: 10 mg orally administered immediately before bedtime (ensure a period of at least 7-8 hours of uninterrupted sleep).
• Geriatric Population: 5 mg/maximum authorized dosage strictly to mitigate the risk of nocturnal mental confusion, falls, and bone fractures.
• Kidney Failure: Does not require special dose adjustments, but requires caution.
• Liver Failure: Compensated cirrhosis: Mandatory decrease the initial and maintenance dose to 5 mg/day.

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Contraindications

• Acute or chronic decompensated respiratory failure.
• Severe obstructive sleep apnea syndrome (OSAS) due to the risk of upper airway collapse during induced deep sleep.
• Severe decompensated liver failure (marked risk of encephalopathy).
• Personal history of complex sleep behaviors associated with hypnotics (pharmacological sleepwalking).

Adverse Effects (ADR)

Security alert · Parasomnias and Sleepwalking

Zolpidem can induce sleep parasomnias and complex unconscious motor behaviors, including violent sleepwalking, unconscious driving, compulsive eating, and nocturnal telephone calls from which the patient has absolute retrograde amnesia the next morning. The risk increases if high doses or concomitant intake of alcohol are associated.

• CNS: Transient anterograde amnesia if the patient does not lie down immediately after ingestion, postural dizziness, visual hypnagogic hallucinations of early onset, sudden rebound insomnia if the drug is discontinued without gradual reduction.
• Dependency: Although less than benzodiazepines, it is associated with a moderate risk of habituation and tolerance after treatments longer than 4 weeks.

Clinical Interactions

• CYP3A4 enzyme inhibitors: Ketoconazole or erythromycin double the half-life of zolpidem, prolonging its sedative effect the next morning.
• CNS depressants: Dangerous synergy with alcohol, opiates and benzodiazepines.

Pregnancy and Breastfeeding

FDA Category: C. Increased risk of preterm birth and low birth weight documented in retrospective cohort studies after exposure in late gestation. Breastfeeding: Compatible with caution. Its excretion in milk is minimal (Relative Infant Dose <1.5%); monitor drowsiness or mild hypotonia in the infant.