Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: mirtazapine

BRAND NAME: Remeron

DRUG CLASS AND MECHANISM: Mirtazapine is in a class of medications called tetracyclic antidepressants that includes maprotiline (Ludiomil). Although the precise mechanism of action of this class of antidepressants is not known, they increase the amount of norepinephrine and serotonin in the brain. Norepinephrine and serotonin are neurotransmitters, chemicals that nerves use to communicate with each other. Mirtazapine also acts as an antihistamine similar to diphenhydramine (Benadryl). Mirtazapine was approved by the FDA in 1996.

GENERIC AVAILABLE: Yes

PRESCRIPTION: Yes

PREPARATIONS: Tablets: 7.5, 15, 30, and 45 mg

STORAGE: Tablets should be stored at room temperature, 15-30°C (59-86°F).

PRESCRIBED FOR: Mirtazapine is used for the treatment of major depression.

DOSING: The usual starting dose for mirtazapine is 15 mg once daily, usually at bedtime. Doses may be increased every 1-2 weeks up to a maximum dose of 45 mg daily. It may be taken with or without food.

DRUG INTERACTIONS: Mirtazapine adds to the sedating effects of alcohol and other drugs that can cause sedation such as the benzodiazepine class of anti-anxiety drugs (e.g., Valium, Ativan, Klonopin, Xanax), the narcotic class of pain medications and its derivatives (e.g., Percocet, Vicodin, Dilaudid, Codeine, Darvon), the tricyclic class of antidepressants (e.g., Elavil, Tofranil, Norpramin), certain antihypertensive medications (e.g., Catapres, Inderal), and some antihistamines (e.g., Benadryl; Atarax; Vistaril).

Fluvoxamine (Luvox) may increase the levels of mirtazapine in the blood which may lead to increased side effects from mirtazapine.

Because of the possibility of developing an increased body temperature (hyperpyrexia), high blood pressure, or seizures, use of mirtazapine is not recommended together with monoamine oxidase inhibitors (MAO's), such as furazolidone (Furoxone), phenelzine (Nardil), procarbazine (Matulane), selegiline (Carbex), or tranylcypromine (Parnate). An interval of 14 days is recommended between stopping MAO inhibitor therapy and starting mirtazapine and vice versa.

PREGNANCY: There are no adequate studies of mirtazapine in pregnant women . Thus, physicians must balance potential benefits against potential risks when considering mirtazapine therapy in pregnant women.

NURSING MOTHERS: It is not known if mirtazapine is secreted in breast milk.

SIDE EFFECTS: Approximately half of the patients who take mirtazapine develop sleepiness. For this reason, it usually is taken at bedtime. In clinical trials, about 1 in 10 persons had to stop therapy because of this side effect. About 1 in 14 persons develop dizziness, and 1 in 6 develop an increase in appetite. Some persons experience weight gain, sometimes requiring discontinuation of treatment. Mirtazapine may increase blood levels of cholesterol and triglycerides. One in four persons develops a dry mouth.

If antidepressants are discontinued abruptly, withdrawal symptoms such as dizziness, headache, nausea, changes in mood may occur. Such symptoms may occur when even a few doses of antidepressant are missed. Therefore, it is recommended that the dose of antidepressant be reduced gradually when therapy is discontinued. Antidepressants may increase the risk of suicide in children and adolescents. There are concerns that antidepressants may also induce suicide in adults. Patients with major depression may experience worsening of depression or suicidal thoughts regardless of whether or not they are treated. Therefore, patients started on antidepressants should be closely observed for signs of worsening, suicidal thinking or change in behavior.

Reference: FDA Prescribing Information