Can Metoprolol Cause Diarrhea?
Yes, metoprolol can cause diarrhea, occurring in approximately 5% of patients (about 5 of 100 patients) according to FDA labeling data. 1
Evidence from FDA Drug Labeling
The FDA-approved prescribing information for metoprolol explicitly lists diarrhea as a documented adverse reaction:
- Diarrhea occurs in about 5 of 100 patients treated with oral metoprolol for hypertension and angina 1
- This makes diarrhea one of the more common gastrointestinal side effects, alongside nausea, dry mouth, gastric pain, constipation, flatulence, and heartburn (each occurring in about 1 of 100 patients) 1
- Vomiting was noted as a "common occurrence" in clinical trials 1
Supporting Evidence from Clinical Trials
Large-scale cardiovascular outcomes trials confirm gastrointestinal effects of beta-blockers:
- In the COPERNICUS trial comparing carvedilol to placebo, diarrhea occurred in 24 patients (6%) on beta-blocker therapy with an adjusted odds ratio of 2.11 (95% CI 1.32-3.39, p=0.0019), representing a statistically significant increase 2
- Nausea showed an adjusted odds ratio of 1.99 (95% CI 1.16-3.42, p<0.05) in beta-blocker trials 2
Mechanism and Clinical Context
While the exact mechanism is not fully elucidated, beta-blockers can disrupt gastrointestinal motility and mucosal function:
- Drug-induced diarrhea can result from multiple mechanisms including altered transit time, secretory changes, and disrupted gut metabolism 3, 4
- Beta-blockers as a class have been implicated in causing diarrhea, with over 700 drugs total known to cause this adverse effect 3
- A case report documented severe diarrhea with propranolol (another beta-blocker) that resolved upon discontinuation and recurred with rechallenge 5
Clinical Management Considerations
If diarrhea develops on metoprolol:
- Consider whether the symptom is tolerable and self-limiting, as many gastrointestinal side effects improve with continued use 4
- Rule out other causes including concurrent medications (particularly ACE inhibitors, which can cause bowel angioedema with diarrhea), infections, and dietary factors 6
- If severe or persistent, consider dose reduction or switching to an alternative antihypertensive or anti-anginal agent 1
- Symptomatic treatment with loperamide or diphenoxylate-atropine may be appropriate for mild cases 4
- Monitor for dehydration and electrolyte abnormalities, particularly hypokalemia, if diarrhea is moderate to severe 7
Important Caveats
- The 5% incidence represents a relatively common adverse effect that should be discussed with patients when initiating therapy 1
- Diarrhea is generally mild and transient in most cases 8
- This side effect should not automatically preclude metoprolol use, as the cardiovascular benefits often outweigh this manageable adverse effect 8
- Document the temporal relationship between metoprolol initiation/dose escalation and diarrhea onset to establish causality 3