Home Drug Guide Doxepin Hydrochloride

Drug Guide

Generic Name

Doxepin Hydrochloride

Brand Names Sinequan, Zonalon, Silenor

Classification

Therapeutic: Antidepressant, Tricyclic

Pharmacological: Tricyclic antidepressant (TCA)

FDA Approved Indications

Major depressive disorder
Anxiety disorders
Insomnia (Silenor)
Pruritus (Zonalon)

Mechanism of Action

Doxepin inhibits the reuptake of norepinephrine and serotonin, increasing their levels in the brain. It also has antihistamine properties contributing to sedative effects.

Dosage and Administration

Adult: Various doses depending on indication, e.g., for depression typically 75-300 mg/day in divided doses or at bedtime.

Pediatric: Not generally recommended for pediatric depression. Use with caution if prescribed for other indications.

Geriatric: Start at lower doses due to increased sensitivity and risk of side effects.

Renal Impairment: Adjust dose cautiously; consider renal function.

Hepatic Impairment: Use with caution; dose adjustment may be necessary.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Widely distributed, crosses the blood-brain barrier.

Metabolism: Primarily hepatic via CYP450 enzymes.

Excretion: Via urine as metabolites and unchanged drug.

Half Life: Approx. 8-24 hours, variable.

Contraindications

Recent myocardial infarction
Use with monoamine oxidase inhibitors (MAOIs)

Precautions

History of urinary retention, angle-closure glaucoma, seizure disorders, bipolar disorder, suicidality, and hepatic impairment.

Adverse Reactions - Common

Drowsiness (Common)
Dizziness (Common)
Dry mouth (Common)
Constipation (Common)

Adverse Reactions - Serious

Suicidal thoughts (Less common but serious)
Serotonin syndrome (Rare)
Cardiac arrhythmias (Rare)
Hepatotoxicity (Rare)

Drug-Drug Interactions

Monoamine oxidase inhibitors (MAOIs)
Other CNS depressants
QT prolonging agents

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for depression severity, suicidal ideation, cardiac status, hydration status.

Diagnoses:

Risk for injury related to sedation or orthostatic hypotension.
Risk for cardiac arrhythmias.

Implementation: Administer at bedtime for sedative effects. Monitor cardiac function if necessary.

Evaluation: Assess for therapeutic response and adverse effects.

Patient/Family Teaching

Do not discontinue abruptly to avoid withdrawal symptoms.
Warn about drowsiness and advise against operating heavy machinery.
Avoid alcohol and CNS depressants.
Report worsening depression or suicidality.

Special Considerations

Black Box Warnings:

Increased risk of suicidal thinking and behavior in children, adolescents, and young adults.

Genetic Factors: Consider CYP2D6 metabolism status for dose considerations.

Lab Test Interference: N/A

Overdose Management

Signs/Symptoms: Seizures, hallucinations, severe hypotension, coma.

Treatment: Supportive care, activated charcoal if ingestion recent, sodium bicarbonate for cardiotoxicity, and intensive medical monitoring.

Storage and Handling

Storage: Store at room temperature, protected from light and moisture.

Stability: Stable under recommended conditions.