What are the common side effects of mirtazapine (Remeron) Orally Disintegrating Tablets (ODT)?

Common Side Effects of Mirtazapine ODT

The most common side effects of mirtazapine orally disintegrating tablets are sleepiness (23%), dry mouth (25%), increased appetite (11%), and weight gain (10%), with sedation being the most frequently reported adverse effect. 1, 2

Most Frequent Side Effects

The side effect profile of mirtazapine ODT is identical to standard mirtazapine tablets, as the formulation does not alter the drug's pharmacology:

• Sedation/Somnolence occurs in approximately 23% of patients (versus 14% with placebo), making it the most common side effect 1
• Dry mouth affects approximately 25% of patients (versus 16% with placebo) 1
• Increased appetite occurs in about 11% of patients (versus 2% with placebo) 1
• Weight gain is reported in approximately 10% of patients (versus 1% with placebo) 1
• Dizziness is commonly reported alongside the above symptoms 2

Gastrointestinal Effects

• Constipation or diarrhea can occur, though mirtazapine essentially lacks the gastrointestinal symptoms typical of SSRIs 3
• Nausea may occur but is less common than with serotonergic antidepressants 3

Neuropsychiatric Effects

• Sleep disorders are reported, though the sedative effects often improve insomnia when the medication is taken at bedtime 3
• Anxiety can occur paradoxically in some patients 3
• Headache is a commonly reported side effect 3
• Fatigue beyond the expected sedation may occur 3

Important Clinical Considerations

Mirtazapine causes more sedation and weight gain than most other antidepressants, which distinguishes it from SSRIs and SNRIs 1. This side effect profile can be advantageous in specific clinical situations:

• The sedative effects are beneficial for patients with insomnia when dosed at bedtime 1
• Weight gain potential is therapeutic in patients with anorexia or unintended weight loss 1
• Mirtazapine has minimal cardiovascular and anticholinergic effects compared to tricyclic antidepressants 4
• It essentially lacks sexual dysfunction, a major advantage over SSRIs 4, 5

Dose-Related Patterns

• Sedation appears paradoxically less frequent at higher dosages (30-45 mg), as the antihistaminic effects that cause somnolence are more prominent at lower doses (15 mg) 5, 6
• Tolerance to sedation may develop over the first 1-2 weeks of treatment 5

Serious but Rare Side Effects

While not "common," clinicians must remain vigilant for:

• Agranulocytosis occurs in approximately 1 in 1,000 patients but is usually reversible when the medication is stopped 7
• Patients should be instructed to report fever, sore throat, flu-like symptoms, or infections immediately 2