AMITRIPTYLINE oral

Therapeutic action

• Tricyclic antidepressant

Indications

• Neuropathic pain
• Major depression (preferably use selective serotonin re-uptake inhibitors for this indication) 

Forms and strengths

• 25 mg tablet

Dosage

Neuropathic pain 

• Adult: 25 mg once daily at bedtime (Week 1); 50 mg once daily at bedtime (Week 2); 75 mg once daily at bedtime (as of Week 3) 

Major depression

• Adult: 25 mg once daily at bedtime. Depending on efficacy and tolerance, increase over 8 to 10 days, up to 75 mg once daily at bedtime.

Do not exceed 150 mg daily. Reduce the dose by half in older patients.

Duration

• Neuropathic pain: 3 to 6 months after pain relief is obtained. If pain reappears, recommence treatment.
• Major depression: at least 9 months. Discontinue treatment gradually (over 4 weeks). If signs of relapse or withdrawal occur, increase the dose then decrease it more gradually.

Contra-indications, adverse effects, precautions

• Do not administer to patients with recent myocardial infarction, arrhythmia, closed-angle glaucoma, prostate disorders.
• Administer with caution and carefully monitor use in older patients and in patients with epilepsy, chronic constipation, renal or hepatic impairment (reduce the dose by half), history of bipolar disorders and suicidal ideation.
• May cause:
  • drowsiness (caution when driving or operating machinery), orthostatic hypotension, sexual dysfunction;
  • anticholinergic effects: dry mouth, constipation, blurred vision, tachycardia, disorders of micturition. Treatment should be discontinued in the event of severe reactions (confusional state, urinary retention, cardiac rhythm disorders);
• Administer with caution and monitor combination with: CNS depressants (opioid analgesics, sedatives, H1 antihistamines, etc.), drugs known to have anticholinergic effects (atropine, chlorpromazine, promethazine, etc.), drugs which lower the seizure threshold (antipsychotics, mefloquine, etc.), serotonergic drugs (SSRI, tricyclic antidepressants, ondansetron, tramadol, etc.), anti-hypertensive drugs.
• Avoid alcohol during treatment (increased risk of adverse effects).
• Pregnancy: re-evaluate whether the treatment is still necessary; if it is continued, maintain amitriptyline at effective dose. Observe the neonate the first few days (risk of agitation, tremors, hypotonia, respiratory difficulties, sleeping disorders, etc.) if the mother was under treatment in the 3^rd trimester of pregnancy. If treatment for major depression starts during pregnancy, preferably use sertraline.
• Breast-feeding: monitor the child for excessive somnolence.

Remarks

• Sedative effect occurs following initial doses, analgesic effect is delayed for 7 to 10 days and the antidepressant effect is delayed for at least 4 weeks. This must be explained to the patient.
• For neuropathic pain, amitriptyline is often administered in combination with carbamazepine or gabapentin.

Storage