Mirtazapine – Atypical antidepressant with sedating and appetite-stimulating effects.
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What is Mirtazapine?
Mirtazapine is a unique atypical antidepressant that’s particularly valuable for patients with depression accompanied by insomnia, poor appetite, or weight loss. Its distinctive side effect profile of sedation and appetite stimulation can be therapeutic benefits for the right patients.
Book an online consultation if you’re experiencing depression with sleep problems, poor appetite, or weight loss, or if other antidepressants haven’t been effective. Our GPs can assess whether Mirtazapine’s unique profile matches your specific symptoms and provide appropriate monitoring for side effects.
What is Mirtazapine used for?
- Major depressive disorder
- Depression with insomnia
- Depression with poor appetite/weight loss
- Anxiety disorders
- Post-traumatic stress disorder (PTSD)
- Chronic pain with depression
- Sleep disorders (off-label low-dose use)
How does Mirtazapine work?
An atypical antidepressant that blocks specific serotonin and noradrenaline receptors while enhancing their release, and also blocks histamine receptors, providing mood improvement with sedating and appetite-stimulating effects.
Dosage and Administration
Adults
Starting dose 15mg at bedtime, increased to 30-45mg daily as needed. Maximum 45mg daily.
Children
Not recommended for children and adolescents under 18 years.
Important Notes
- Take once daily at bedtime due to sedating effects.
- Can be taken with or without food.
- May take 2-4 weeks to see full antidepressant effects.
- Do not stop suddenly—gradual dose reduction required.
Side Effects
Common Side Effects
- Sedation and drowsiness
- Increased appetite and weight gain
- Dry mouth
- Constipation
- Dizziness
- Fatigue
- Vivid dreams or nightmares
Serious Side Effects
Seek immediate medical attention if you experience:
- Thoughts of self-harm or suicide (especially when starting)
- Blood disorders (agranulocytosis - very rare)
- Severe allergic reactions
- Serotonin syndrome (when combined with other antidepressants)
- Severe skin reactions
- Liver problems (rare)
Important Warnings
- May increase thoughts of self-harm, especially in young adults—close monitoring required.
- Causes significant weight gain in many patients—discuss with GP if concerning.
- Very sedating—take at bedtime and avoid driving next day until effects are known.
- Report any signs of infection (fever, sore throat) due to rare blood disorder risk.
- Tell your GP if you have liver disease, kidney problems, or heart disease.
Drug Interactions
Tell your GP if you're taking any of the following medications:
- MAOIs—dangerous interaction, must avoid completely.
- Other antidepressants—risk of serotonin syndrome.
- Warfarin—may increase bleeding risk.
- Alcohol—significantly increases sedation.
- Sedating medications—additive drowsiness effects.
- Tramadol—increased risk of serotonin syndrome.
Frequently Asked Questions
Why does Mirtazapine cause weight gain?
Mirtazapine blocks histamine receptors and affects appetite-regulating brain circuits, leading to increased appetite and food cravings, particularly for carbohydrates.
How is Mirtazapine different from SSRIs?
Unlike SSRIs, Mirtazapine enhances both serotonin and noradrenaline release through receptor blockade, and has pronounced sedating and appetite-stimulating effects.
Can Mirtazapine help with sleep problems?
Yes, the sedating effects often improve sleep within days of starting, even before the antidepressant effects begin. Some doctors prescribe low doses specifically for sleep.
Is the weight gain reversible?
Weight gain may continue throughout treatment, but typically levels off after several months. Weight usually returns to baseline gradually after stopping the medication.
Medically Reviewed by: Mohammed Hassan - Independent Prescriber
Last Updated: 2025-01-14