Amitriptyline

# Amitriptyline ## Overview - **Classification**: Tricyclic Antidepressant (TCA). - **Mechanism**: Blocks reuptake of norepinephrine and serotonin. Also has anticholinergic, antihistaminic, and alpha-adrenergic blocking properties. ## Primary Indications 1. **Major Depressive Disorder (MDD)** - Treatment of depressive symptoms. 2. **Neuropathic Pain** - Chronic pain conditions (e.g., diabetic neuropathy, post-herpetic neuralgia). 3. **Migraine Prophylaxis** - Prevention of migraine headaches. 4. **Insomnia** - Off-label for sleep due to sedative effects. ## Adult Dosing ### Standard Dosing **Major Depressive Disorder** - **Dose**: Initial **25-75 mg/day** (outpatient); **100-150 mg/day** (hospitalized). - **Frequency**: Once daily at bedtime or in divided doses. - **Route**: Oral. - **Maximum**: Outpatient **150 mg/day**; Hospitalized **300 mg/day**. - **Considerations**: Start low and titrate slowly every 3-7 days. **Neuropathic Pain / Migraine Prophylaxis / Insomnia** - **Dose**: Initial **10-25 mg**. - **Frequency**: Once daily at bedtime. - **Route**: Oral. - **Maximum**: **100-150 mg/day** (for pain/migraine). - **Considerations**: Lower doses often effective, titrate based on response. ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment generally needed. Use with caution in severe impairment. - **Hepatic Impairment**: Reduce dose significantly (e.g., **50%** of usual starting dose). Monitor closely. - **Elderly Patients**: Start at **10 mg** at bedtime. Titrate slowly. Increased risk of anticholinergic and cardiovascular effects. Max **50 mg/day** often sufficient. ## Pediatric Dosing **Note**: Amitriptyline is generally not first-line for depression in pediatrics due to suicidality risk. Use for pain/migraine is off-label. ### Neonates (0-28 days) - **Not recommended**. ### Infants (1-12 months) - **Not recommended**. ### Children (1-12 years) **Neuropathic Pain / Migraine Prophylaxis** - **Dose**: Start **0.1-0.2 mg/kg**. - **Frequency**: Once daily at bedtime. - **Maximum**: **1 mg/kg/day** or **50 mg/day**, whichever is less. - **Special Notes**: ECG recommended before and during therapy. Monitor for suicidality. ### Adolescents (13-18 years) **Neuropathic Pain / Migraine Prophylaxis** - **Dose**: Start **10 mg**. - **Frequency**: Once daily at bedtime. - **Maximum**: **75 mg/day**. - **Special Notes**: Depression use discouraged due to suicidality risk. ECG recommended. Monitor for suicidality. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to amitriptyline or other TCAs. - **Absolute**: Concomitant use with MAOIs (within **14 days** of MAOI discontinuation). - **Absolute**: Acute recovery phase after myocardial infarction. - **Absolute**: Untreated narrow-angle glaucoma. - **Absolute**: Severe heart block or arrhythmias. ### Common Adverse Effects - **Very Common (>10%)**: Dry mouth, blurred vision, constipation, urinary retention, sedation/drowsiness, weight gain. - **Common (1-10%)**: Orthostatic hypotension, tachycardia, dizziness, tremor, headache, nausea, confusion (esp. elderly). - **Serious but Rare**: Arrhythmias (QT prolongation, Torsades de Pointes), seizures, suicidal ideation, bone marrow suppression, hepatic dysfunction, serotonin syndrome. ### Key Drug Interactions - **MAOIs**: Risk of hyperpyretic crisis, convulsions, death (serotonin syndrome). **Contraindicated**. - **CNS Depressants (alcohol, opioids, benzodiazepines)**: Potentiated sedation. Avoid concomitant use. - **Anticholinergics (antihistamines, antipsychotics)**: Increased anticholinergic effects (e.g., severe constipation, urinary retention). - **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine)**: Can significantly increase amitriptyline levels. Reduce amitriptyline dose. - **Sympathomimetics (e.g., epinephrine, norepinephrine)**: Enhanced cardiovascular effects. ## Monitoring & Follow-up - **Before Treatment**: Baseline ECG (especially if cardiac risk factors), BP, HR. Assess suicidal ideation. - **During Treatment**: Monitor BP (orthostatic), HR, mental status, suicidal ideation (especially at initiation/dose changes). ECG monitoring if high doses or cardiac risk. - **Clinical Signs**: Watch for worsening depression/suicidality, new or worsening cardiac symptoms, severe anticholinergic effects, confusion. ## Clinical Pearls - 💡 **Tip 1**: Administer at **bedtime** due to significant sedative and anticholinergic effects. - 💡 **Tip 2**: For neuropathic pain and migraine, much **lower doses** are typically effective compared to depression. - 💡 **Tip 3**: **Titrate dose slowly** to minimize side effects, especially in elderly or sensitive patients. - 💡 **Tip 4**: Antidepressant effects may take **2-4 weeks** to manifest, but sedative effects are immediate. - 💡 **Tip 5**: Avoid **abrupt discontinuation** after prolonged use to prevent withdrawal symptoms (e.g., flu-like, sleep disturbances). Taper gradually. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.