mirtazapine at a glance
Medicine class
Antidepressant; centrally acting presynaptic alpha-2 antagonist.
Licensed use
Episodes of major depression in adults.
Food
Can be taken with or without food.
Alertness
May cause sleepiness or impaired concentration; do not drive or use machinery if affected.
What is mirtazapine used for?
Mirtazapine is licensed for:
Treatment of episodes of major depression in adults.
How does mirtazapine work?
Mirtazapine blocks presynaptic alpha-2 receptors, increasing noradrenaline and serotonin transmission. It also blocks certain serotonin receptors and histamine H1 receptors; histamine blockade contributes to sleepiness.
mirtazapine preparations and strengths
Dispersible tablet
Route: Oral
Strengths: 15 mg, 30 mg, 45 mg
Oral solution
Route: Oral
Strengths: 15 mg/mL
How to take mirtazapine
Follow the dispensing label and product leaflet. Mirtazapine may be taken with or without food.
Swallow film-coated tablets whole with water.
Place an orodispersible tablet on the tongue and allow it to disintegrate; it can be swallowed without water.
Measure oral solution with the supplied oral syringe, not a kitchen teaspoon. It may be swallowed directly, placed on a spoon or mixed into a glass of water.
mirtazapine side effects
Common or expected effects
- Sleepiness or sedation
- Increased appetite and weight gain
- Dry mouth
- Headache
- Dizziness or tiredness
- Nausea, vomiting, diarrhoea or constipation
Get urgent medical advice
- New or worsening suicidal thoughts or behaviour
- Severe allergic reaction
- Blistering, peeling or widespread rash
- Fever, sore throat or mouth ulcers, which may indicate a blood-cell disorder
- Confusion, persistent headache, weakness or muscle cramps, which may indicate low blood sodium
- Serotonin syndrome, including agitation or confusion, fever, sweating, muscle rigidity or jerking and gastrointestinal symptoms
- Seizure, mania, jaundice, pancreatitis or a serious abnormal heart rhythm
mirtazapine in pregnancy
Mirtazapine can be used during pregnancy when recommended after an individual benefits-and-risks discussion. Current UK information does not show an increased risk of impaired development, miscarriage or stillbirth, but exposure near delivery may cause temporary newborn adaptation symptoms and, rarely, breathing problems. Discuss pregnancy planning or a positive pregnancy test with the prescriber rather than stopping suddenly.
mirtazapine while breastfeeding
Mirtazapine passes into breast milk in small amounts and may be used cautiously when the infant is full-term and healthy, although alternatives may be preferred when starting treatment. Monitor for unusual drowsiness or irritability, gastrointestinal symptoms, poor feeding, difficulty waking for feeds and appropriate weight gain. Seek specialist advice for a premature or unwell infant.
mirtazapine interactions
Check all prescribed, pharmacy and herbal medicines before combining them with mirtazapine.
Monoamine oxidase inhibitors (MAOIs)
The combination is contraindicated because a serious interaction may occur; specialist switching advice is required.
Other serotonergic medicines, including SSRIs, SNRIs, tramadol, triptans, linezolid, lithium and buprenorphine
May increase the risk of serotonin syndrome and requires clinical assessment and monitoring.
Common questions about mirtazapine
Answers are fully visible for fast scanning and source review.
How long does mirtazapine take to work?
Some changes may appear earlier, but full antidepressant benefit commonly takes several weeks. Contact the prescriber if symptoms worsen or there are thoughts of self-harm.
Is mirtazapine a sleeping tablet?
No. It is an antidepressant, although its antihistamine effect can cause sleepiness.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.