What is mirtazapine, and how does it work (mechanism of action)?

Mirtazapine is a tetracyclic antidepressant similar to maprotiline (Ludiomil) and tricyclic antidepressants, for example, desipramine (Norpramin). Depression is an all-pervasive sense of sadness and gloom. It is believed that in some patients with depression, abnormal levels of neurotransmitters (chemicals that nerves use to communicate with each other) may be the cause of their depression. Mirtazapine elevates mood by raising the level of neurotransmitters (norepinephrine and serotonin) in nerves of the brain. Mirtazapine also blocks the effect of histamine. Mirtazapine was approved by the FDA in 1996.

What brand names are available for mirtazapine?

Remeron, Remeron SolTab

Is mirtazapine available as a generic drug?

GENERIC AVAILABLE: Yes

Do I need a prescription for mirtazapine?

Yes

What are the side effects of mirtazapine?

The most common side effects of mirtazapine include drowsiness,

• dry mouth,
• weight gain,
• increased appetite, increased
• cholesterol and
• triglycerides,
• dizziness,
• constipation,
• confusion, and
• abnormal dreams.

Other important side effects that could potentially be serious include

• seizures,
• abnormal heart beats,
• low blood pressure upon standing
• (orthostatic hypotension),
• manic episodes, and
• decreased blood cells.

What is the dosage for mirtazapine?

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.

Which drugs or supplements interact with mirtazapine?

Mirtazapine adds to the sedating effects of alcohol and other drugs that can cause sedation such as:

• the benzodiazepine class of anti-anxiety drugs (for example, diazepam [Valium], lorazepam [Ativan], clonazepam [Klonopin], alprazolam [Xanax, Xanax XR, Niravam]),
• the narcotic class of pain medications and its derivatives (for example, oxycodone and acetaminophen [Percocet, Roxicet, Tylox, Endocet], hydrocodone/acetaminophen [Vicodin, Vicodin ES, Anexsia, Lorcet, Lorcet Plus, Norco], hydromorphone [Dilaudid], codeine, propoxyphene [Darvon]),
• the tricyclic class of antidepressants (for example, amitriptyline [Elavil, Endep], imipramine [Tofranil], desipramine [Norpramin]),
• certain antihypertensive medications (for example, clonidine [Catapres], propranolol [Inderal, Inderal LA, Innopran XL), and
• some antihistamines (for example, diphenhydramine [Benadryl], hydroxyzine [Atarax, Vistaril]).

Fluvoxamine (Luvox), ketoconazole (Nizoral) and cimetidine (Tagamet) may increase the levels of mirtazapine in the blood which may lead to increased side effects from mirtazapine. Carbamazepine (Tegretol) and phenytoin (Dilantin) decrease the blood concentration of mirtazapine by increasing the breakdown of mirtazapine in the liver, possibly reducing the effect of mirtazapine.

Mirtazapine should not be used with monoamine oxidase (MAO) inhibiting drugs such as phenelzine (Nardil), procarbazine (Matulane), selegiline (Eldepryl), or tranylcypromine (Parnate). High fever, convulsions, and even death can occur from such combinations. Therefore, an interval of 14 days is recommended between stopping MAO inhibitor therapy and starting mirtazapine, and vice versa. Similar reactions may occur if mirtazapine is combined with other drugs that increase serotonin activity in the brain. Such drugs to avoid include tryptophan, sumatriptan (Imitrex), linezolid (Zyvox), fluoxetine (Prozac), venlafaxine (Effexor), lithium (Eskalith, Lithobid), tramadol (Ultram), and St. John's wort.

Is mirtazapine safe to take if I'm pregnant or breastfeeding?

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.

It is not known if mirtazapine is secreted in breast milk.

What else should I know about mirtazapine?

What preparations of mirtazapine are available?

Tablet (Orally disintergrating): 15, 30, and 45 mg

How should I keep mirtazapine stored?

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