From the Guidelines
Yes, mirtazapine (Remeron) can cause constipation as a side effect, as it is one of the most commonly reported adverse events associated with this medication, according to studies such as 1 and 1. Constipation occurs in patients taking this antidepressant medication due to its antihistamine and anticholinergic properties, which can slow down gut motility. To manage constipation while taking mirtazapine, patients can try:
- Increasing fluid intake to at least 6-8 glasses of water daily
- Adding more fiber to their diet (aiming for 25-30 grams per day)
- Engaging in regular physical activity
- Maintaining a consistent bathroom routine If dietary changes are insufficient, over-the-counter stool softeners or mild laxatives may help. However, if constipation becomes severe or persistent despite these measures, it is essential to consult a healthcare provider, as they may adjust the dosage, recommend specific treatments for constipation, or consider alternative medications, as noted in studies like 1 and 1. Never discontinue mirtazapine suddenly without medical supervision, as this can cause withdrawal symptoms. It is crucial to weigh the benefits of mirtazapine against its potential side effects, including constipation, and to closely monitor patients for any adverse events, as emphasized in the studies 1.
From the FDA Drug Label
Table 4: Adverse Reactions (≥1% and greater than placebo) in 6-Week U. S Clinical Studies of Mirtazapine Tablets in Patients with MDD Mirtazapine Tablets (n=453) Placebo (n=361) ... Digestive System ... Constipation 13% 7%
Constipation is a reported adverse reaction associated with the use of mirtazapine. According to the data, 13% of patients who received mirtazapine experienced constipation, compared to 7% of patients who received placebo 2.
From the Research
Mirtazapine and Constipation
- Mirtazapine is known for its unique mechanism of action as a noradrenergic and specific serotonergic antidepressant (NaSSA) 3, 4, 5.
- The studies suggest that mirtazapine has minimal anticholinergic effects 3, 4, 6, which are often associated with constipation.
- Common adverse effects of mirtazapine include somnolence, increased appetite, weight gain, and dizziness 7, 5, but constipation is not explicitly mentioned as a common side effect.
- In contrast to selective serotonin reuptake inhibitors (SSRIs), mirtazapine has no significant serotonergic effects such as gastrointestinal symptoms 3, 6, which implies a lower likelihood of causing constipation.
Comparison with Other Antidepressants
- Mirtazapine's side effect profile is different from tricyclic antidepressants and SSRIs, with less alpha 1 adrenergic and muscarinic blockade, and less nausea and sexual dysfunction 4, 6.
- The lack of significant anticholinergic and serotonergic effects suggests that mirtazapine may have a lower risk of causing constipation compared to other antidepressants 3, 4, 6.