Za Pharmacy
Drugs, Supplies and Delivery
Amitriptyline
Amitriptyline is a tricyclic antidepressant (TCA) widely used for the treatment of depression, neuropathic pain, and migraine prophylaxis. Known for its potent effects on serotonin and norepinephrine reuptake, it is also associated with significant anticholinergic and sedative side effects. This article synthesizes information from the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of amitriptyline, including its mechanism, uses, dosing, side effects, precautions, drug interactions, and availability.
Amitriptyline inhibits the reuptake of serotonin (5-HT) and norepinephrine (NE) at presynaptic neurons, increasing their availability in the synaptic cleft. This enhances mood regulation and pain modulation. Additionally, it blocks:
- Histamine H1 Receptors: Causes sedation.
- Muscarinic Acetylcholine Receptors: Leads to anticholinergic effects (e.g., dry mouth, constipation).
- Alpha-1 Adrenergic Receptors: Contributes to orthostatic hypotension (Lippincott Textbook of Pharmacology).
- Major Depressive Disorder (MDD):
- Effective for severe depression, though less commonly used due to side effects (BNF).
- Neuropathic Pain:
- First-line treatment for diabetic neuropathy, postherpetic neuralgia, and fibromyalgia (Lange Basic & Clinical Pharmacology).
- Migraine Prophylaxis:
- Reduces the frequency and severity of migraines.
- Chronic Tension-Type Headache:
- Used off-label for prevention.
- Insomnia:
- Low doses are sometimes used for sleep disturbances (Lippincott).
- Adults:
- Depression: Start with 25–50 mg at bedtime, titrate to 75–150 mg/day in divided doses or as a single nighttime dose (BNF).
- Neuropathic Pain/Migraine: Start with 10–25 mg at bedtime, titrate to 50–150 mg/day (Lange Basic & Clinical Pharmacology).
- Elderly:
- Start with 10 mg at bedtime, titrate cautiously to avoid side effects (Lippincott).
Administration:
- Take at bedtime to minimize daytime sedation.
- Avoid abrupt discontinuation; taper gradually over weeks to prevent withdrawal symptoms (BNF).
- Common: Dry mouth, constipation, blurred vision, sedation, weight gain, and orthostatic hypotension (BNF).
- Serious:
- Cardiac Arrhythmias: Due to QT prolongation, especially in overdose.
- Seizures: Increased risk in predisposed individuals.
- Hyponatremia: Especially in elderly patients (Lippincott).
- Suicidal Ideation: Increased risk in adolescents and young adults (Lange Basic & Clinical Pharmacology).
- Contraindications:
- Recent myocardial infarction, arrhythmias, or severe liver disease.
- Concurrent use of MAO inhibitors (BNF).
- Monitoring:
- ECG in patients with cardiac risk factors.
- Serum sodium levels in elderly patients (Lippincott).
- Pregnancy/Lactation:
- Category C: Use only if benefits outweigh risks; potential neonatal withdrawal.
- Excreted in breast milk—consult a specialist (Lange Basic & Clinical Pharmacology).
- MAO Inhibitors: Risk of serotonin syndrome; allow a 14-day washout period (BNF).
- CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine): Increase amitriptyline levels; monitor for toxicity.
- Anticholinergic Drugs (e.g., antihistamines, antipsychotics): Enhanced anticholinergic effects.
- QT-Prolonging Drugs (e.g., amiodarone, antipsychotics): Increased risk of arrhythmias (Lippincott).
Amitriptyline is the generic name. Brand names include Elavil® and Lentizol®. Generic formulations are widely available as:
- Tablets: 10 mg, 25 mg, 50 mg.
- Oral Solution: 10 mg/5 mL (BNF).
