Which SSRIs Cause Constipation
Paroxetine is the SSRI most likely to cause constipation due to its anticholinergic activity, which distinguishes it from other SSRIs that typically do not cause this side effect. 1
Paroxetine's Unique Constipating Profile
- Paroxetine has weak affinity for muscarinic cholinergic receptors, unlike other SSRIs which have negligible anticholinergic effects 2
- This anticholinergic activity makes paroxetine more sedating and constipating compared to other SSRIs 1
- Constipation was among the most frequently reported adverse events with paroxetine in long-term use, though rates were not significantly different from comparator antidepressants 3
- In panic disorder trials, constipation occurred in patients receiving paroxetine 10-60 mg/day, though specific incidence rates were lower than other common side effects like nausea and headache 2
Other SSRIs and Constipation
- Most SSRIs (fluoxetine, citalopram, escitalopram, sertraline, fluvoxamine) do not typically cause constipation 4
- In a comprehensive meta-analysis of gastrointestinal side effects, escitalopram and sertraline were associated with all gastrointestinal side effects EXCEPT constipation and increased appetite 4
- SSRIs generally increase gastrointestinal motility through increased serotonin concentration at nerve endings, which would theoretically prevent rather than cause constipation 5
Clinical Context from IBS Guidelines
- The AGA guidelines note that TCAs cause constipation as an adverse effect due to their anticholinergic properties, but this is not mentioned as a concern with SSRIs 6
- When treating IBS-C patients, secondary amine TCAs are preferred over tertiary amine TCAs due to lower anticholinergic effects (and thus less constipation), but SSRIs are not recommended at all for IBS regardless of subtype 6
Critical Pitfall to Avoid
Do not assume all SSRIs cause constipation equally—this is a medication-specific effect primarily seen with paroxetine due to its unique pharmacologic profile among SSRIs 1. If constipation is a concern, consider alternative SSRIs like escitalopram, sertraline, or fluoxetine which lack anticholinergic activity 4.