Amitriptyline

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Definition

Amitriptyline is a medication used to treat various forms of depression, pain associated with the nerves (neuropathic pain), and to prevent migraine headaches. It is sold in the United States under the brand names Elavil and Endep.

Purpose

Amitriptyline helps relieve depression and pain. This medication, usually given at bedtime, also helps patients sleep better.

Description

This medication is one of several tricyclic antidepressants, so-called because of the three-ring chemical structure common to these drugs. Amitriptyline acts to block reabsorption of neurotransmitters (chemicals that transmit nerve messages in the brain ). Amitriptyline and the other tricyclic antidepressants are primarily used to treat mental depression but are increasingly being replaced by a newer and more effective group of antidepressant drugs called selective serotonin reuptake inhibitors (SSRIs). Amitriptyline is sometimes prescribed to help treat pain associated with cancer. In addition, it is sometimes prescribed for various types of chronic pain. Tablets are available in 10, 25, 50, 70, and 150 mg.

Recommended dosage

The usual adult dose for pain management ranges from 10 mg to 150 mg at bedtime. Patients are generally started on a low dose and the amount may be increased as needed. Side effects, such as a dry mouth and drowsiness, may make it difficult to increase the dose in older adults. Bedtime dosing helps the patient sleep. Doctors generally prescribe 75–150 mg for depression. It is given at bedtime or in divided doses during the day. It may take 30 days for the patient to feel less depressed. Pain relief is usually noticed sooner than the mood change. Teens and older adults usually receive a lower dose. If the nightly dose is missed, it should not be taken the next morning. Taking amitriptyline during waking hours could result in noticeable side effects. Patients should check with their doctor if the daily dose is missed. Those on more than one dose per day should take a missed dose as soon as it is remembered but should not take two doses at the same time. While amitriptyline is usually administered orally, injectable amitriptyline is available. It should not be used in this form long-term; patients should switch to tablets as soon as possible.

Precautions

Patients should not stop taking this medication suddenly. The dose should gradually be decreased, then discontinued. If the drug is stopped abruptly, the patient may experience headache, nausea, or discomfort throughout the body, and a worsening of original symptoms. The effects of the medication last for three to seven days after it has been stopped, and older patients usually are more prone to some side effects such as drowsiness, dizziness, mental confusion, blurry vision, dry mouth, difficulty urinating, and constipation. Taking a lower dose may help resolve these problems. Patients may need to stop this medication before surgery.

Amitriptyline should not be given to anyone with allergies to the drug or to patients recovering from a heart attack. Patients taking the monoamine oxidase inhibitors (MAOIs) Parnate ( tranylcypromine ) and Nardil ( phenelzine ) —different types of antidepressants—should not use amitriptyline in combination. It should be administered with caution to patients with glaucoma, seizures , urinary retention, overactive thyroid, poor liver or kidney function, alcoholism, asthma, digestive disorders, enlarged prostate, seizures, or heart disease. This medication should not be given to children under 12 years of age. Pregnant women should discuss the risks and benefits of this medication with their doctor as fetal deformities have been associated with taking this drug during pregnancy. Women should not breast feed while using amitriptyline.

Side effects

Common side effects include dry mouth, drowsiness, constipation, and dizziness or lightheadedness when standing. Patients can suck on ice cubes or sugarless hard candy to combat the dry mouth. Increased fiber in the diet and additional fluids may help relieve constipation. Dizziness is usually caused by a drop in blood pressure when suddenly changing position. Patients should slowly rise from a sitting or lying position if dizziness is noticed. Amitriptyline may increase the risk of falls in older adults. Patients should not drive or operate machinery or appliances while under the influence of this drug. Alcohol and other central nervous system depressants can increase drowsiness. Amitriptyline may also produce blurry vision, irregular or fast heartbeat, high or low blood pressure, palpitations, and an increase or decrease in a diabetic patient's blood sugar levels. Patients' skin may become more sensitive to the sun and thus direct sunlight should be avoided by wearing protective clothing and the application of sunscreen with a protective factor of 15 or higher.

Amitriptyline may increase appetite, cause weight gain, or produce an unpleasant taste in the mouth. It may also cause diarrhea, vomiting, or heartburn. Taking this medication with food may decrease digestive side effects. Other less likely side effects include muscle tremors, nervousness, impaired sexual function, sweating, rash, itching, hair loss, ringing in the ears, or changes in the makeup of the patient's blood. Patients with schizophrenia may develop an increase in psychiatric symptoms.

Interactions

Patients should always tell all doctors and dentists that they are taking this medication. It may decrease the effectiveness of some drugs used to treat high blood pressure and should not be taken with other antidepressants, epinephrine and other adrenaline-type drugs, or methylphenidate . Patients should not take over-thecounter medications without checking with their doctor. For instance, amitriptyline should not be taken with Tagamet (cimetidine) or Neosynephrine. Patients taking this drug should avoid the dietary supplements St. John's wort , belladonna, henbane, and scopolia. Black tea may decrease the absorption of this drug. Patients should ingest the drug and tea at least two hours apart.

See also Depression and depressive disorders

Resources

BOOKS

Consumer Reports Staff. Consumer Reports Complete Drug Reference. 2002 ed. Denver: Micromedex Thomson Healthcare, 2001.

Ellsworth, Allan J. and others. Mosby's Medical Drug Reference, 2001–2002. St. Louis: Mosby, 2001.

Hardman, Joel G. and Lee E. Limbird, eds. Goodman and Gilman's The Pharmacological Basis of Therapeutics. 10th ed. New York: McGraw-Hill, 2001.

Mosby's GenRx Staff. Mosby's GenRx. 9th ed. St. Louis: Mosby, 1999.

Venes, Donald and Clayton L. Thomas. Taber's Cyclopedic Medical Dictionary. 19th ed. Philadelphia: F. A. Davis, 2001.

Mark Mitchell, M.D.