Amitriptyline Hydrochloride
Indications
Amitriptyline Hydrochloride is indicated in-
- Depressive Illness: particularly where sedation is required.
- Nocturnal Enuresis in children.
- Prophylaxis of Migraine.
- Tension Headache.
- Chronic Pain.
Description
Amitriptyline is a tricyclic
antidepressant. It has marked anticholinergic and sedative properties.
It prevents the reuptake of noradrenaline and serotonin at the nerve
ending. Amitriptyline hydrochloride is rapidly absorbed from the Gl
tract. Peak plasma concentrations occur within 2-12 hours. Amitriptyline
is excreted in the urine, mainly in the form of its metabolites.
Pharmacology
The mechanism of action of this drug is not
fully elucidated. It is suggested that amitriptyline inhibits the
membrane pump mechanism responsible for the re-uptake of transmitter
amines, such as norepinephrine and serotonin, thereby increasing their
concentration at the synaptic clefts of the brain. These amines are
important in regulating mood. The monoamine hypothesis in depression,
one of the oldest hypotheses, postulates that deficiencies of serotonin
(5-HT) and/or norepinephrine (NE) neurotransmission in the brain lead to
depressive effects. This drug counteracts these mechanisms, and this
may be the mechanism of amitriptyline in improving depressive symptoms.
Whether its analgesic effects are related to its mood-altering
activities or attributable to a different, less obvious pharmacological
action (or a combination of both) is unknown.
Dosage & Administration
Depression: Initially 75
mg (Elderly and Adolescents 30-75 mg) daily in divided doses or as a
single dose at bedtime increased gradually as necessary to 150-200 mg;
Child under 16 years not recommended for depression.
Nocturnal Enuresis: Child 7-10 years: 10-20 mg, 11-16 years: 25-50 mg at night; max. period of treatment (including gradual withdrawal) 3 months-full physical examination before the further course.
Prophylaxis of Migraine: 100 mg daily.
Tension Headache: 10-25 mg three times daily.
Nocturnal Enuresis: Child 7-10 years: 10-20 mg, 11-16 years: 25-50 mg at night; max. period of treatment (including gradual withdrawal) 3 months-full physical examination before the further course.
Prophylaxis of Migraine: 100 mg daily.
Tension Headache: 10-25 mg three times daily.
Interaction
TCA enhances the sedative effect of alcohol
and opioid analgesics. When TCA is used with Moxifloxacin or
Terfenadine, it increases the risk of ventricular arrhythmias.
Disulfirum and Cimetidine inhibit the metabolism of Amitriptyline. When
TCA is used with diuretics, it enhances the risk of postural
hypotension.
Contraindications
Amitriptyline is contraindicated in
myocardial infarction, arrythmias, particularly heart block of any
degree, mania and severe liver disease. Initially, sedation may affect
the ability to drive or operate machinery.
Side Effects
- Anticholinergic: Excessive perspiration, dry mouth, blurred vision, hyperpyrexia, urinary retention and urinary tract dilatation.
- Cardiovascular reactions: Hypotension, syncope, postural hypotension, hypertension, tachycardia, palpitations, myocardial infarction, etc.
- CNS and Neuromuscular: Confusional states, disturbed concentration, disorientation, delusions, etc.
- Allergic: Skin rash, urticaria, photosensitization, etc.
- Haematological: Bone-marrow depression.
- Gastrointestinal: Nausea, epigastric distress, vomiting, anorexia, stomatitis, unpleasant taste, weight loss, diarrhoea, constipation, etc.
- Endocrine: Testicular swelling, gynaecomastia, breast enlargement, galactorrhoea, etc.
Pregnancy & Lactation
Pregnancy Category C. Amitriptyline has
been shown to cross the placenta. Amitriptyline should be used during
pregnancy only if the potential benefit to the mother justifies the
potential risk to the fetus. Amitriptyline is excreted into breast milk.
Because of the potential for serious adverse reactions in nursing
infants from Amitriptyline, a decision should be made whether to
discontinue nursing or to discontinue the drug, taking into account the
importance of the drug to the mother.
Precautions & Warnings
It should be used with caution in patients
with a history of epilepsy, glaucoma, urinary retention, cardiac
disease, diabetes, pregnancy, hepatic impairment, thyroid disease,
increased intra-ocular pressure and psychoses (may aggravate mania).
Therapeutic Class
Tricyclic Anti-depressant
Storage Conditions
Store in a cool and dry place, below 30°C. Protect from light and moisture.
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