Mirtazapine (Remeron): Uses, Dosage, Side Effects, and What to Expect

Mirtazapine (brand name: Remeron) is a noradrenergic and specific serotonergic antidepressant (nassa). Mirtazapine has a unique mechanism: it blocks alpha-2 adrenergic autoreceptors (increasing norepinephrine and serotonin release), 5-HT2A receptors (reducing anxiety and improving sleep), 5-HT2C receptors (increasing appetite), 5-HT3 receptors (reducing nausea), and histamine H1 receptors (causing sedation). At lower doses, H1 antagonism dominates (more sedation). At higher doses, noradrenergic activation partially counteracts sedation, which is why 15 mg is often more sedating than 30 mg — the 'paradoxical dose-response.'

• Major Depressive Disorder

Common off-label uses:

• Insomnia (very commonly prescribed at low doses for sleep)
• Appetite stimulation (cachexia, anorexia)
• Nausea and vomiting (5-HT3 blockade)
• PTSD nightmares
• Generalized Anxiety Disorder
• Social Anxiety Disorder
• Augmentation in treatment-resistant depression

Start 15 mg at bedtime. May increase to 30-45 mg. For depression, 30-45 mg is typically needed. For insomnia/appetite: 7.5-15 mg at bedtime. Available as regular tablets and orally disintegrating tablets (SolTab).

Sedative and appetite effects from the first dose. Antidepressant effects take 2-4 weeks.

• Sedation and somnolence (most common, strongest at low doses)
• Increased appetite and weight gain (significant — average 2-4 kg)
• Dry mouth
• Constipation
• Elevated cholesterol and triglycerides
• Dizziness

• Agranulocytosis (rare but potentially fatal — seek immediate care for fever/infection signs)
• Serotonin syndrome (when combined with other serotonergic drugs)
• Suicidal ideation in young adults (FDA black box warning)
• Significant metabolic effects with long-term use
• Hepatotoxicity (rare)

Contraindicated with MAOIs. Additive sedation with alcohol and other CNS depressants. Caution with other serotonergic drugs. CYP3A4 and CYP1A2 substrate — levels affected by strong inhibitors and inducers.

Category C. Limited data. Some studies suggest low teratogenic risk but insufficient to confirm safety.

Taper over 1-2 weeks. Discontinuation symptoms include insomnia, nausea, anxiety, and irritability — generally milder than SSRI/SNRI discontinuation.