COMPOSITION: Each tablet contains 10 mg (25 mg) of Amitriptyline HCl.
PHARMACOLOGICAL CLASSIFICATION: A 1.2 Psychoanaleptics.
PHARMACOLOGICAL ACTION: Amitriptyline inhibits the membrane pump mechanism responsible for re-uptake of noradrenaline into adrenergic neurons. Pharmacologically this action may potentiate or prolong sympathetic activity, since re-uptake of noradrenaline is important physiologically in terminating its transmitting actions. This interference with re-uptake of noradrenaline is believed by some to underline the antidepressant activity of amitriptyline. The precise mechanism of action in man has not yet been confirmed. It is not a monoamine oxidase inhibitor and it does not act primarily by stimulation of the central nervous system.
INDICATIONS: Amitriptyline is an tricyclic antidepressant used in the treatment of patients with endogenous depression. It also possesses mild tranquillising and sedative properties which is helpful in alleviating anxiety or agitation that often accompanies depression. It has been used with benefit in depression of long or short duration. All patients do not respond to the same degree. Some may respond in 4 to 10 days while others may require up to 30 days to obtain benefit. Lack of response may occur occasionally.
CONTRA-INDICATIONS: Amitriptyline is contra-indicated in patients who have shown prior hypersensitivity to it.
It should not be given concomitantly with a monoamine oxidase inhibiting compound. Hyperpyretic crises, severe convulsions and deaths have occurred in patients receiving tricyclic antidepressant and monoamine oxidase inhibiting drugs simultaneously. When it is desired to substitute amitriptyline for a monoamine oxidase inhibitor, a minimum of 14 days should be allowed to elapse after the latter is discontinued. Amitriptyline should then be initiated cautiously with gradual increases in doses until optimum response is achieved.
Amitriptyline is not recommended for use during the acute recovery phase following myocardial infarction because it has been reported to produce arrhythmias, sinus tachycardia and prolongation of the conduction time.
Amitriptyline should not be administered concurrently with antihypertensive medicine, particularly adrenergic blocking agents such as Guanethidine. Safe use of amitriptyline during pregnancy and lactation has not been established.
Amitriptyline should not be given to children under 12 years of age.
WARNING: This medicine should at all times be kept out of reach of children, as even small doses may be fatal to them.
Drowsiness is often experienced at the start of amitriptyline therapy and patients if affected should not drive or operate machinery.
DOSAGE AND DIRECTIONS FOR USE:
Initially 75 mg to 150 mg daily in divided doses.
Maintenance dose is 50 mg to 100 mg daily in divided doses.
SIDE-EFFECTS AND SPECIAL PRECAUTIONS: Many side-effects of amitriptyline are caused by its anticholinergic actions. These include dry mouth, sour or metallic taste, constipation which may lead to paralytic ileus, urinary retention, pupillary dilatation with blurred vision and disturbances in visual accommodation, palpitations, tachycardia and impotence.
Other adverse effects include drowsiness (but sometimes nervousness and insomnia may occur), headache, peripheral neuropathy, tremor, orthostatic hypotension, hypertension, dizziness, sweating, weakness and fatigue, ataxia, epileptiform seizures, extrapyramidal symptoms including speech difficulties, tinnitus, stomatitis and gastric irritation with nausea and vomiting. Confusion or delirium may occur, particularly in the elderly. Anorexia with mass loss, or mass gain may occur. Allergic skin reactions and photosensitisation have been reported and, less frequently, cholestatic jaundice and blood disorders, including eosinophilia, bone-marrow depression, thrombocytopenia, leucopenia and agranulocytosis.
Amitriptyline has an adverse effect on the myocardium and can cause conduction defects and cardiac arrhythmias; an increased risk of sudden death has been suspected in cardiac patients receiving tricyclic antidepressants. Thus amitriptyline should be used with caution in patients with cardiovascular disease and should be avoided in the immediate recovery phase after myocardial infarction and in patients with heart block.
Endocrine effects include changes in libido, interference with sexual function, gynaecomastia and breast enlargement, and galactorrhoea. Changes in blood sugar concentrations may also occur and, less frequently, inappropriate secretion of antidiuretic hormone.
Caution should be observed with patients suffering from a depressive phase of manic depressive psychosis, as occasionally mania can be precipitated in such patients. Withdraw the drug if the depression turns into a manic phase. Patients with suicidal tendencies should be carefully supervised during treatment.
The pressor effects of the direct-acting sympathomimetic agents, adrenaline and noradrenaline, are enhanced by amitriptyline, and local anaesthetics containing these vasoconstrictors should be avoided as hypertensive reactions may occur. When possible, treatment should be discontinued several days before elective surgery. The hypotensive effect of certain antihypertensive agents may be reduced.
The use of amitriptyline in patients suffering from acute forms of porphyria, especially variegate porphyria and to a lesser extent acute intermittent porphyria and hereditary coproporphyria, is contentious, and thus Trepiline should be used with caution in these patients.
Amitriptyline should also be used with caution in patients with hyperthyroidism or with impaired liver function, and in those with a history of epilepsy, untreated narrow-angle glaucoma, urinary retention, prostatic hypertrophy, or constipation.
Central nervous system depressants including alcohol and anticholinergic agents can have their effects increased by amitriptyline. NOTE:Elderly patients are more prone to all these effects, and therapy should be initiated at lower than standard doses in the elderly. KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT: Symptoms of overdosage are excitement and restlessness with marked anticholinergic effects, including dryness of the mouth, dilated pupils, tachycardia, urinary retention, and intestinal stasis. Severe symptoms include unconsciousness, convulsions and myoclonus, hyperreflexia, hypotension, and respiratory and cardiac depression, with life-threatening cardiac arrhythmias that may recur some days after apparent recovery.
Treatment is symptomatic and supportive.