Mirtazapine

Definition

Mirtazapine is most commonly used to treat depression. Mirtazapine is available in the United States under the trade names of Remeron and Remeron SolTab.

Mirtazapine, sold under the trade name Remeron, is taken by mouth and swallowed whole. Remeron SolTabs should be allowed to dissolve in the mouth. No water is needed when taking the SolTabs, since these tablets disintegrate in saliva and are not swallowed whole.

Purpose

Mirtazapine is best known for treating depression. However, it may also be used for treating anxiety or to make people drowsy just before surgery.

Description

Mirtazapine is usually thought of as an antidepressant, or a drug that alleviates symptoms of depression. Approved by the Federal Drug Administration (FDA) in 1996, it is believed to alter the activities of some chemicals in the brain and, in this way, reduce chemical imbalances responsible for causing depression and anxiety. As with all antidepressants, it may take several weeks of treatment before full beneficial effects are seen. Mirtazapine is broken down by the liver and eliminated from the body mostly by the kidneys. It is supplied in 15-, 30-, and 45-mg tablets.

Recommended dosage

The recommended initial dose of mirtazapine in 15 mg taken at bedtime. The dose may be increased in 15-mg increments every one or two weeks as needed until symptoms of depression or anxiety resolve. Typical doses range between 15 and 45 mg. Dosages above 45 mg per day are not recommended. Elderly people or those with liver or kidney disease should use mirtazapine carefully, since they may be more sensitive to some of the drug's side effects.

Precautions

Mirtazapine may cause weight gain and may increase cholesterol levels and should be used carefully in overweight individuals and those with high cholesterol levels. If symptoms of fever, sore throat, or irritation in the mouth occur, a health care provider should be notified. Rarely, mirtazapine may lower blood counts, causing people to be at an increased risk of serious complications, including infections. Mirtazapine may increase the tendency for seizures. As a result, it should be used carefully in people with epilepsy or other seizure disorders. Mirtazapine may alter moods or cause mania. It should be used carefully in people with a history of mania. Mirtazapine may alter liver function and should be used cautiously by those with a history of liver disease. If abdominal pain, yellowing of the skin or eyes, darkening of urine, or itching occurs, a health care provider should be notified immediately.

More than 50% of individuals using mirtazapine report feeling sleepier than normal and 7% feel dizzy. As a result, people taking mirtazapine should not participate in activities that require mental alertness—like driving— until they know how the drug will affect them. Because there is an increased likelihood of suicide in depressed individuals, close supervision of those at high risk for suicide attempts using this drug is recommended. Mirtazapine is not recommended in pregnant or breast-feeding women.

Side effects

The most common side effects that cause people to stop taking mirtazapine are sleepiness and nausea. Other common side effects are dizziness, increased appetite and weight gain. Less common adverse effects include weakness and muscle aches, flu-like symptoms, low blood-cell counts, high cholesterol, back pain, chest pain, rapid heartbeats, dry mouth, constipation, water retention, difficulty sleeping, nightmares, abnormal thoughts, vision disturbances, ringing in the ears, abnormal taste in the mouth, tremor, confusion, upset stomach, and increased urination.

Interactions

Use of mirtazapine with antidepressants referred to as monoamine oxidase inhibitors (MAOIs) such as Parnate (tranylcypromine) and Nardil (phenelzine), is strongly prohibited due to the potential for high fever, muscle stiffness, sudden muscle spasms, rapid changes in heart rate and blood pressure, and the possibility of death. In fact, there should be a lapse of at least 14 days between taking an MAOI and mirtazapine.

Because mirtazapine may cause drowsiness, it should be used carefully with other medications that also make people prone to sleepiness, such as antidepressants, antipsychotics, antihistamines, anti-anxiety agents, and alcohol. Increased sleepiness has been reported when mirtazapine was used with both alcohol and the anti-anxiety drug diazepam.

See also Depression and depressive disorders

BOOKS

Ellsworth, Allan J., and others. Mosby's Medical Drug Reference. St. Louis, MO: Mosby, Inc, 1999.

Facts and Comparisons Staff. Drug Facts and Comparisons. 6th Edition. St. Louis, MO: Facts and Comparisons; Philadelphia: Lippincott Williams and Wilkins, 2002.

Organon Staff. Remeron Package Insert. West Orange, NJ: Organon Inc, 2001.

Kelly Karpa, RPh, Ph.D.