Amitriptyline Hydrochloride

Trade Names:
Amitriptyline
- Tablets 10 mg
- Tablets 25 mg
- Tablets 50 mg
- Tablets 75 mg
- Tablets 100 mg
- Tablets 150 mg

Mechanism of Action

Pharmacology

Inhibits presynaptic reuptake of norepinephrine and serotonin in CNS.

Pharmacokinetics

Absorption

Rapidly absorbed.

Metabolism

Metabolized in the liver by N-demethylation and bridge hydroxylation. Nortriptyline is an intermediate active metabolite.

Elimination

50% to 66% excreted in the urine within 24 h. Excreted as glucuronide or sulfate conjugate of metabolites. A small amount of unchanged drug excreted in the urine. T _½ is 31 to 46 h.

Special Populations

May have increased plasma levels. Dosage adjustment may be necessary.

Indications and Usage

Relief of depression. Endogenous depression is more likely to be alleviated than are other depressive states.

Unlabeled Uses

Management of chronic pain associated with migraine, tension headache, phantom limb pain, tic douloureux, diabetic neuropathy, peripheral neuropathy, cancer or arthritis; treatment of panic and eating disorders.

Contraindications

Hypersensitivity to any tricyclic antidepressant; use during acute recovery phase of MI; concomitant use with MAOIs, except under close medical supervision; may block the antihypertensive action of guanethidine or similarly active compounds.

Dosage and Administration

Titrate dosage over 2 wk to 1 mo. Give maintenance dose 6 mo to 1 yr. Do not interrupt therapy abruptly; reduce over 2 wk period.

PO 75 to 150 mg/day in divided doses; give in evening or at bedtime because of sedative effects.

PO 100 to 300 mg/day.

PO 10 mg 3 times daily and 20 mg at bedtime.

PO 40 to 100 mg/day.

General Advice

Give drug with or immediately after food or fluid and in late afternoon or at bedtime because of sedative effect. Tablets may be crushed.

Storage/Stability

Store at room temperature and protect from light.

Drug Interactions

May cause decreased blood levels of amitriptyline.

May cause increased blood levels of amitriptyline.

Use with product may result in hypertensive crisis.

Depressant effects may be additive.

May cause hyperpyretic crises, severe convulsions, and death when given with amitriptyline.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Orthostatic hypotension; hypertension; tachycardia; palpitations; arrhythmias; ECG changes.

CNS

Confusion; hallucinations; disturbed concentration; decreased memory; delusions; nervousness; restlessness; agitation; panic; insomnia; nightmares; mania; exacerbation of psychosis; drowsiness; dizziness; weakness; emotional lability; numbness; tremors; extrapyramidal symptoms (eg, pseudoparkinsonism, movement disorders, akathisia); seizures.

Dermatologic

Rash; pruritus; photosensitivity reaction; dry skin; acne; itching.

EENT

Conjunctivitis; blurred vision; increased IOP; mydriasis; tinnitus; nasal congestion; peculiar taste in mouth.

GI

Nausea; vomiting; anorexia; GI distress; diarrhea; flatulence; dry mouth; constipation.

Genitourinary

Impotence; sexual dysfunction; menstrual irregularities; dysmenorrhea; nocturia; urinary frequency; UTI; vaginitis; cystitis; urinary retention and hesitancy.

Hematologic

Bone marrow depression, including agranulocytosis; eosinophilia; purpura; thrombocytopenia; leukopenia.

Hepatic

Jaundice.

Metabolic

Elevation or depression of blood sugar levels.

Respiratory

Pharyngitis; rhinitis; sinusitis; cough.

Miscellaneous

Breast enlargement.

Precautions

Pregnancy

Category D .

Lactation

Excreted in breast milk.

Children

Not recommended for children younger than 12 yr of age.

Special Risk Patients

Caution is needed with history of seizures; urinary retention; urethral or ureteral spasm; angle-closure glaucoma or increased IOP; cardiovascular disorders; hyperthyroidism and patients receiving thyroid medication; hepatic or renal function impairment; schizophrenia; paranoia.

Changing from MAOI to amitriptyline

Waiting period of 7 to 10 days is necessary to prevent hypertensive crisis.

Serotonin syndrome

Some TCAs inhibit neuronal reuptake of serotonin and can increase synaptic serotonin levels.

Overdosage

Symptoms

Confusion, agitation, hallucinations, seizures, status epilepticus, clonus, choreoathetosis, hyperactive reflexes, positive Babinski's sign, coma, cardiac arrhythmias, renal failure, flushing, dry mouth, dilated pupils, hyperpyrexia.

Patient Information

• Caution patient not to stop taking medication abruptly without consulting health care provider.
• Warn patient of the risk of seizure.
• Reinforce importance of follow-up visits to health care provider for monitoring drug's effectiveness and side effects.
• Explain that drug effects may not be evident for 4 to 6 wk but that side effects are usually noted early.
• Patient should complete the full course of therapy.
• Tell patient that side effects are reduced if drug is taken at bedtime.
• Advise patient that weight gain often results from increased appetite caused by drug.
• Inform patient that urine may turn blue-green.
• Emphasize the need for regular dental care because oral dryness can increase risk for dental caries.
• Instruct patient to report the following symptoms to health care provider: blurred vision, sore throat, fever, increased heart rate, impaired coordination, difficult urination, excessive sedation, or seizures.
• Instruct patient to take sips of water frequently, suck on ice chips or sugarless hard candy, or chew sugarless gum if dry mouth occurs.
• Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
• Instruct patient to avoid intake of alcohol beverages or other CNS depressants.
• Advise patient that drug may cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness.
• Caution patient to avoid exposure to sunlight, and to use sunscreen or wear protective clothing to avoid photosensitivity reaction.

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