Does Mirtazapine Cause Thirst?
Dry mouth, not thirst per se, is a common side effect of mirtazapine, occurring in approximately 25% of patients (versus 16% with placebo), which may secondarily lead to increased fluid intake. 1
Primary Side Effect: Dry Mouth (Xerostomia)
The most relevant side effect related to your question is dry mouth (xerostomia), which is well-documented in the literature:
- Dry mouth occurs in approximately 25% of mirtazapine-treated patients compared to 16% with placebo, making it one of the more common adverse effects 1
- This anticholinergic-type effect can create a sensation that may prompt increased water consumption, though mirtazapine actually has very weak muscarinic anticholinergic properties compared to tricyclic antidepressants 2
Most Common Side Effects (For Context)
The predominant side effects of mirtazapine are actually different from dry mouth:
- Sedation/somnolence is the most frequently reported side effect at approximately 23% (versus 14% placebo) 1
- Increased appetite occurs in about 11% (versus 2% placebo) 1
- Weight gain affects approximately 10% (versus 1% placebo) 1
- Constipation is another frequently reported gastrointestinal effect 1
Clinical Implications
Mirtazapine's side effect profile is generally favorable compared to other antidepressants, with minimal cardiovascular effects and essentially lacking the gastrointestinal symptoms, insomnia, and sexual dysfunction common with SSRIs 1. The dry mouth effect, while present, is typically transient and manageable 2, 3.
Important Caveat
If you experience what feels like excessive thirst (polydipsia) rather than just dry mouth, this would be atypical for mirtazapine and should prompt evaluation for other causes, as this is not a characteristic side effect documented in the clinical literature 2, 4, 5.