Mirtazapine (Remeron, Zispin, Remergil, etc.)

Mirtazapine has been produced by Organon Biosciences International since 1966. It has a unique chemical structure and unique properties. It is a tetracyclic antidepressant and it increases serotonin and norepinephrine in the synaptic cleft through a different mechanism than other antidepressants.

The Bottom Line: What You Really Need to Know


Mirtazapine is approved for the treatment of mild to severe depression. It is also used to treat Panic Disorder, anxiety, OCD, PTSD and hives. Mirtazapine is not usually used as a first line antidepressant; rather, it is often added to duloxetine or venlefaxine to treat severe or resistant depression.

Dosage and instructions

The usual starting dose for mirtazapine is 15 mg/day at bedtime. The dose can be slowly increased to a maximum of 45 mg/day. Mirtazapine is available as a dissolving tablet and can be taken without food or water.

How mirtazapine works

Depression is thought to be caused by an inadequate amount of certain neurotransmitters in the gap between nerve cells (the synaptic cleft or gap). Antidepressants work in different ways to increase the levels of some of the neurotransmitters.

Mirtazapine increases the level of norepinephrine by blocking receptors that keep it from being released. It increases serotonin levels the same way, plus it may improve transmission between nerve cells by enhancing serotonin uptake in the post-synaptic cell.

Mirtazapine doesn't have much of an effect on other neurotransmitters except for histamine. It blocks histamine much the same as Benedryl does.

Side effects

The most common effects that people experience while taking mirtazapine are increased appetite, weight gain, drowsiness, nausea and headache. Other side effects that have been reported include:


Although mirtazapine does not interact with medications to the degree that other antidepressants do, there are some potential drug interactions you should be aware of.

MAOI antidepressants: Mirtazapine should not be taken within two weeks of taking a MAOI antidepressant. A serious reaction that includes high fever, high blood pressure and seizures could result.

Sedating medications: Mirtazapine has a sedating effect, and if you take other sedating medications with it, the effects will be enhanced. Narcotics, barbiturates, sleeping pills, antianxiety pills and antihistamines can all cause oversedation when taken with mirtazapine.

Other medications that interact with mirtazapine include tricyclic antidepressants, some blood pressure medications and fluvoxamine.

Warnings, precautions and contraindications

Suicide risk: There appears to be an increased risk for suicide with all antidepressants, especially when you first start taking them. Anyone who starts taking a new antidepressant should be monitored for several weeks for potential suicidal thoughts. You should see your physician or therapist weekly and have someone check on you every day to see how you are doing. If they notice or you experience any of the following, it should be reported to the doctor immediately:

Bipolar disorder: Mirtazapine should not be used in treating bipolar disorder unless mood stabilizers are also being used. It can precipitate manic episodes that may be mild or severe, and can lead to delusions, psychosis and rapid cycling.

Agranulocytosis: A few people have developed agranulocytosis while taking mirtazapine. This is a condition in which there are very few disease-fighting cells in your bloodstream, which makes you susceptible to infections. Notify your doctor if you experience mouth sores, sores that won't heal or become easily infected, fever, sore throat or any other unusual symptoms.

Mirtazapine should be used with caution in people who have any of the following conditions:

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