Mirtazapine Side Effects

Updated February 12, 2018

Mirtazapine is a medication prescribed to treat major depression. Sold in generic form and under the brand names Remeron, Zispin and Avanza, mirtazapine belongs to the class of drugs called tetracyclic antidepressants. Numerous side effects are possible.

Most Common Effect

In clinical studies with mirtazapine, the most common side effect was drowsiness, occurring in more than half the participants. The drug is usually taken at bedtime because of this side effect, but drowsiness is still a common reason people stop using mirtazapine.

Other Common Effects

Other common side effects in the mirtazapine clinical studies included dry mouth, increased appetite, weight gain, high cholesterol and triglyceride levels, constipation, dizziness and weakness.

Less Common Effects

Between 1 to 5 per cent of participants experienced abnormal dreams, abnormal thoughts, confusion, fever and chills, fluid retention, frequent urination, muscle pain or back pain, and shakiness or tremors.


As with all other antidepressant medications, the U.S. Food and Drug Administration requires a black box warning on mirtazapine labelling. The warning addresses increased risk of suicidal thoughts and behaviour in children and adolescents. Mirtazapine is not approved for treating anyone under age 18.

Drug Interactions

Mirtazapine can interact with many drugs. These include alcohol, anti-anxiety medications, antihistamines, high blood pressure medicine, monoamine oxidase inhibitors, narcotic medications, tranquillisers and other antidepressants.

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About the Author

Shelley Moore is a journalist and award-winning short-story writer. She specializes in writing about personal development, health, careers and personal finance. Moore has been published in "Family Circle" magazine and the "Milwaukee Sentinel" newspaper, along with numerous other national and regional magazines, daily and weekly newspapers and corporate publications. She has a Bachelor of Science in psychology.