Mirtazapine
Always check the BNF link here before prescribing.
Mirtazapine is an antidepressant commonly used in primary care and psychiatry. It is often preferred in elderly patients due to its sedative and appetite-stimulating effects.
โ๏ธ Mode of Action
- Classified as a NaSSA (Noradrenaline and Specific Serotonin Antidepressant).
- Blocks central ฮฑโ-adrenergic receptors โ enhances noradrenaline & serotonin release.
- Antagonises 5-HTโ and 5-HTโ receptors, while indirectly stimulating 5-HTโA (improves mood, reduces anxiety).
- Strong Hโ histamine receptor antagonist โ sedation & appetite stimulation.
๐ Indications
- Major depressive disorder (especially in elderly, underweight, or those with insomnia).
- Adjunct in anxiety disorders.
- Occasionally used off-label for insomnia, appetite stimulation in palliative care.
๐ Dose
- Start: 15 mg ON (bedtime due to sedation).
- Titrate: Increase to 30 mg/day over 2โ4 weeks; maximum 45 mg/day.
- โ ๏ธ Lower doses (15 mg) are more sedating than higher doses (30โ45 mg).
๐ Interactions
- โ ๏ธ Avoid with MAOIs (and for 2 weeks after MAOI use).
- ๐ Caution with sedatives (additive CNS depression).
- โ ๏ธ Avoid with artemether/lumefantrine and sibutramine.
- May interact with CYP3A4 inhibitors/inducers (check BNF).
โ Contraindications
- โ Concomitant or recent (within 14 days) MAOI therapy.
- โ Known hypersensitivity to mirtazapine or excipients.
โ ๏ธ Side Effects
- ๐ด Sedation (especially at low doses).
- ๐ฝ๏ธ Increased appetite & weight gain (can be useful in cachectic/elderly patients).
- ๐ Sexual dysfunction (less frequent than SSRIs).
- ๐คข GI upset (nausea, constipation).
- ๐ฉธ Agranulocytosis (rare) โ check FBC if fever, sore throat, or infection symptoms.
- โก Seizures, myoclonus (rare).
- Other: dizziness, dry mouth, abnormal dreams.
๐ References
