Amitriptyline
Mechanism :
Amitriptyline is an antidepressant with sedative effects. Amitriptyline inhibits the membrane pump mechanism responsible for uptake of norepinephrine and serotonin in adrenergic and serotonergic neurons.
Indication :
- Depression
- Nocturnal enuresis
- Idiopathic musculoskeletal pain syndrome
- Analgesia for chronic pain
- Migraine prophylaxis
Contraindications :
Amitriptyline is contraindicated in patients who have shown prior hypersensitivity to it and in acute porphyria, hepatic impairment and cardiovascular disease.
Dosing :
Depressive disorders:
Adolescent: 25-50 mg/day orally in divided doses initially. Then gradually increase to 100 mg/day in divided doses.
Children (off-label): 1 mg/kg/day in divided doses every 8 hourly for first 3 days, followed by 1.5 mg/kg/day oral in divided doses every 8 hours.
Analgesia for chronic pain (off-label):
0.5-2 mg/kg every day at bedtime. Start with 0.1 mg/kg every day at bedtime, titrate slowly over 2-3 weeks.
Idiopathic musculoskeletal pain syndromes:
10-50 mg at bedtime, start at lower dose.
Migraine prophylaxis (off-label):
0.25 mg/kg/day at bedtime; may increase dose by 0.25 mg/kg/day; not to exceed 1 mg/kg/day.
Nocturnal enuresis: Try for 3 months.
For 6-12 years: 10-25 mg PO.
For 12-18 years: 25-50 mg at bedtime PO.
Adverse Effect :
Mainly anticholinergic effects: sedation, postural hypotension, tremor, sweating, arrhythmia, increased appetite and weight gain. Lowered seizure threshold, agranulocytosis, thrombocytopenia, elevated LFTs.
Interaction :
MAOIs: Hyper pyretic crises, severe convulsions, and deaths have occurred in patients receiving tricyclic antidepressant and monoamine oxidase inhibiting drugs simultaneously.
OCPs, Calcium Channel Blockers, Cimetidine, Phenothiazines, SSRIs: Plasma concentration of amitriptyline increased.
Rifampicin, Anti-Coagulants: Decreased plasma concentration of amitriptyline.
Sedatives, Hypotensive, Drugs that prolong QT interval: Increased effects of these drugs.
Hepatic Dose :
Use with caution and preferably reduce the dose. Adjust the dose as per serum concentrations of amitriptyline.