Side Effects of Mirtazapine

Side Effects of Mirtazapine

Mirtazapine is an antidepressant medicine which is used to treat depression and sometimes Obsessive Compulsive Disorder and anxiety. It is used to improve a person’s mood and well-being. It works by restoring the balance of neurotransmitters in the brain. This is a prescription-only medication which can come in either tablet or liquid form.

Mirtazapine, like all drugs, comes with potential risks and side effects. Potential side effects of Mirtazapine include: drowsiness, Lightheadedness; weight gain; increased appetite; dry mouth; constipation and dizziness. These side effects should be considered before prescribing Mirtazapine to a patient, taking into account the patient’s mental and physical history, to decide whether the benefits would outweigh these potential side effects.

Potential medical conditions can increase the risk of side effects. For example, the risk of QT prolongation (a condition that affects heart rhythm) can be increased if you slow heartbeat, heart failure, a family history of certain heart problems such as sudden cardiac death. Low levels of potassium in the blood and the use of diuretics can also increase the risk of Mirtazapine. This reemphasises the importance of considering the history of the patient before prescribing Mirtazapine.

When prescribing Mirtazapine, a consultation should be held in order to discuss the potential side effects with the patient. If the patient has any follow up questions regarding the side effects of Mirtazapine, or the usage, then they can arrange a follow up appointment with the GP in question to discuss this in more detail, in order to ensure that the patient is comfortable with their prescription.


  • WebMD. (2005 - 2021). Mirtazapine Oral. Available: Last accessed 29th Jun 2021.
  • Co-written by The TMLEP Clinical Risk and Patient Safety Publishing Group and Ms Georgia Millington, TMLEP Analyst and Mr Matthew Govier, Prison Experienced Registered General Nurse.. (2021). Side Effects of Mirtazapine. TMLEP Clinical Risk Case Studies. 4 (5), 1.

Important Note

This article is intended to raise awareness to clinical risk issues in an effort to reduce incidence recurrence and improve patient safety. This is not intended to be relied upon as advice. Facts have been altered to ensure this case is non-identifiable, albeit clinical learning points remain applicable. To request an independent clinical review, please contact [email protected] or call +44 (0) 203 355 9796.