Drug Class Description

Generic Name

Drug Description

Presentation

Indications

Adult Dosage

For oral administration only

Therapy should be started with a low dosage and increased gradually, according to the clinical response and any evidence of intolerance.

Adults - initial dosage: Usually 75mg a day in divided doses (or a single dose at night). If necessary, this may be increased to a total of 150mg a day, the additional doses being given in the late afternoon and/or at bedtime. The sedative effect is usually rapidly apparent. The antidepressant activity may be seen within three or four days or may take up to 30 days to develop adequately.

Adults - maintenance dosage: Usually 50 - 100mg a day. For maintenance therapy, the total dosage may be given in a single dose preferably in the evening or at bedtime. When satisfactory improvement has been reached, dosage should be reduced to the lowest amount that will maintain relief of symptoms. Maintenance therapy should be continued for three months or longer to lessen the chances of relapse.

Child Dosage

Children: Due to lack of clinical experience amitriptyline is not recommended for the treatment of depression in children under 16 years of age.

Enuresis: Children aged 6 - 10 years may receive 10 - 20mg a day, while those aged 11 - 16 may need 25 - 50mg a day. Treatment should not exceed three months.

Elderly Dosage

Contra Indications

Amitriptyline should be used with caution in patients with a history of epilepsy, in patients with impaired liver function and, because of its atropine-like action, in patients with a history of urinary retention, prostatic hypertrophy, narrow-angle glaucoma or increased intra-ocular pressure. In patients with narrow-angle glaucoma, even average doses may precipitate an attack of glaucoma.

Patients with cardiovascular disorders, hyperthyroid patients and those receiving thyroid medication or anticholinergic agents should be closely supervised and the dosage of all medications carefully adjusted.

Elderly patients are particularly liable to experience adverse reactions especially agitation, confusion and postural hypotension.

When amitriptyline is used for the depressive component of schizophrenia, psychotic symptoms may be aggravated. In manic depressives, a shift towards the manic phase may occur; paranoid delusions, with or without associated hostility, may be aggravated. In such cases, a major tranquilliser should be given concurrently or the dosage of amitriptyline reduced.

The risk of suicide remains during treatment of depressed patients and until significant remission occurs such patients require careful supervision.

Concurrent administration with ECT may increase the hazards of treatment and should be limited to patients for whom it is deemed essential.

If possible, discontinue amitriptyline several days before surgery. But if emergency surgery is unavoidable, the anaesthetist should be informed that the patient is being treated with amitriptyline because anaesthesia may increase the risk of hypotension and arrhythmias. Behavioural changes have been observed in children receiving tricyclics for the treatment of enuresis.

Hyponatraemia (usually in the elderly and possibly due to inappropriate secretion of antidiuretic hormone) has been associated with all types of antidepressants and should be considered in all patients who develop drowsiness, confusion or convulsions while taking an antidepressant.

Suicide/suicidal thoughts or clinical worsening

Depression is associated with an increased risk of suicidal thoughts, self harm and suicide (suiciderelated events). This risk persists until significant remission occurs. As improvement may not occur during the first few weeks or more of treatment, patients should be closely monitored until such improvement occurs. It is general clinical experience that the risk of suicide may increase in the early stages of recovery.

Other psychiatric conditions for which amitriptyline is prescribed can also be associated with an increased risk of suiciderelated events. In addition, these conditions may be comorbid with major depressive disorder. The same precautions observed when treating patients with major depressive disorder should therefore be observed when treating patients with other psychiatric disorders.

Patients with a history of suiciderelated events, or those exhibiting a significant degree of suicidal ideation prior to commencement of treatment are known to be at greater risk of suicidal thoughts or suicide attempts, and should receive careful monitoring during treatment. A metaanalysis of placebocontrolled clinical trials of antidepressant drugs in adult patients with psychiatric disorders showed an increased risk of suicidal behaviour with antidepressants compared to placebo in patients less than 25 years old.

Close supervision of patients and in particular those at high risk should accompany drug therapy especially in early treatment and following dose changes. Patients (and caregivers of patients) should be alerted about the need to monitor for any clinical worsening, suicidal behaviour or thoughts and unusual changes in behaviour and to seek medical advice immediately if these symptoms present.

Excipient Warnings

This product contains liquid maltitol. Patients with rare hereditary problems of fructose should not take this medicine.

Methyl and propyl hydroxybenzoates are contained in this product which may cause allergic reactions (possibly delayed).

Special Precautions

Interactions

The concurrent use of antidepressants having varying modes of action should be made only with due recognition of their possible potentiation and with a thorough knowledge of their respective pharmacologies. Monoamine oxidase inhibitors can potentiate the effects of tricyclic antidepressants such as amitriptyline and hyperpyretic crises, severe convulsions and fatalities have occurred. A minimum of 14 days should elapse between discontinuing a MAOI and starting amitriptyline which should be introduced cautiously and dosage increased gradually. Amitriptyline may block the antihypertensive action of guanethidine, debrisoquine, betanidine and possibly clonidine. It would be advisable to review all antihypertensive therapy during treatment with tricyclic antidepressants.

Amitriptyline should not be given with sympathomimetic agents such as adrenaline, ephedrine, isoprenaline, noradrenaline, phenylephrine and phenylpropanolamine.

Amitriptyline may enhance the response to alcohol, barbiturates and other CNS depressants. In turn, barbiturates may decrease and methylphenidate may increase, the antidepressant action of amitriptyline. Delirium has been reported in patients taking amitriptyline with disulfiram.

Paralytic ileus may occur in patients taking tricyclic antidepressants in combination with drugs having an anticholinergic action.

Based on the known metabolism of amitriptyline, the protease inhibitor, ritonavir, may increase the serum levels of amitriptyline. Therefore, careful monitoring of therapeutic and adverse effects is recommended when these drugs are administered concommitantly.

Cimetidine is reported to reduce hepatic metabolism of certain tricyclic antidepressants. Caution is advised if patients receive large doses of ethchlorvynol concurrently. Transient delirium has been reported in patients treated with 1g ethchlorvynol and 75mg to 150mg amitriptyline.

St John's Wort may decrease plasma levels of amitriptyline.

Amitriptyline may increase levels of thioridazine leading to cardiac side effects.

Adverse Reactions

In general, amitriptyline is well tolerated. The side effects given below are essentially a combined list of all those of the tricyclic group of antidepressants. Some of them have not been reported with amitriptyline, but are included because of the similar pharmacologies of the group members. As the antidepressant effects of amitriptyline may not become apparent for the first 2-4 weeks of therapy, patients should be closely monitored during this period.

Hypotension, syncope, postural hypotension, hypertension, tachycardia, palpitations, myocardial infarction, arrhythmias, heart block, stroke, non-specific ECG changes and changes in AV-conduction. Arrhythmias and severe hypotension are likely to occur with high dosage or overdose.

CNS and neuromuscular: confusional states, disturbed concentration, disorientation, delusions, hallucinations, hypomania, excitement, anxiety, restlessness, insomnia, nightmares, numbness, tingling and paraesthesiae of the extremities, peripheral neuropathy, inco-ordination, ataxia, tremors, coma, convulsions, alteration of the EEG, extrapyramidal symptoms including abnormal involuntary movements and tardive dyskinesia, dysarthria, tinnitus.

Anticholinergic: dry mouth, blurred vision, disturbance of accommodation, increased intra-ocular pressure, constipation, paralytic ileus, hyperpyrexia, urinary retention, urinary tract dilatation.

Allergic: skin rash, urticaria, photosensitisation, oedema of face and tongue.

Haematological: bone marrow depression including agranulocytosis, leucopenia, eosinophilia, purpura, thrombocytopenia.

Gastro-intestinal: nausea, epigastric distress, vomiting, anorexia, stomatitis, unpleasant taste, diarrhoea, parotid swelling, black tongue, rarely hepatitis (including altered liver function and jaundice).

Endocrine: testicular swelling, gynaecomastia, breast enlargement, galactorrhoea, increased or decreased libido, impotence, interference with sexual function, elevation or lowering of blood sugar levels, syndrome of inappropriate ADH (antidiuretic hormone) secretion.

Other reactions: dizziness, weakness, fatigue, headache, weight loss, increased perspiration, urinary frequency, mydriasis, alopecia, drowsiness, increased appetite and weight gain (may be a drug reaction or due to relief of the depression). Abrupt withdrawal after prolonged administration has caused nausea, headache and malaise. Reports have associated gradual withdrawal with transient symptoms including irritability, restlessness, as well as dream and sleep disturbances during the first two weeks or dosage reduction. These symptoms are not indicative of addictions. Adverse reactions such as withdrawal symptoms, respiratory depression and agitation have been reported in neonates whose mothers had taken tricyclic antidepressants in the last trimester of pregnancy.

Mania or hypomania has been reported rarely within 2-7 days of stopping chronic therapy with tricyclic antidepressants.

Side effects in enuresis: Dosages used in enuresis are low compared with those used in depression and side effects are therefore less frequent. The most common are drowsiness and anticholinergic effects. The only other side effects, reported infrequently at these dosages, have been mild sweating and itching. The recommended dosage must not be exceeded.

Cases of suicidal ideation and suicidal behaviours have been reported during amitriptyline therapy or early after treatment discontinuation.

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