Atorvastatin and Frequent Stools
Atorvastatin does not commonly cause frequent stools, but mild gastrointestinal disturbances including diarrhea can occur in approximately 6.8% of patients taking the medication. 1, 2
Gastrointestinal Side Effects of Atorvastatin
The FDA-approved drug label for atorvastatin reports the following gastrointestinal side effects:
- Diarrhea: 6.8% of patients (compared to 6.3% with placebo)
- Dyspepsia: 4.7% of patients
- Nausea: 4.0% of patients
- Abdominal discomfort, eructation, and flatulence are also reported 1
The incidence of diarrhea appears to be dose-dependent, with higher rates observed at higher doses:
- 7.3% at 10 mg
- 6.4% at 20 mg
- 14.1% at 40 mg
- 5.2% at 80 mg 1
Mechanism of Action and GI Effects
Atorvastatin works by inhibiting HMG-CoA reductase, limiting cholesterol formation. Unlike bile acid sequestrants (such as colesevelam, cholestyramine, and colestipol) that are specifically known to cause constipation as a common side effect, atorvastatin does not directly target intestinal function or bile acid metabolism in a way that would predictably cause frequent stools 3.
Clinical Considerations
When evaluating a patient with frequent stools while on atorvastatin, consider:
Temporal relationship: Did the symptoms begin after starting atorvastatin or after a dose increase?
Rule out other causes:
- Concurrent medications
- Dietary changes
- Underlying gastrointestinal conditions
Management options if atorvastatin is suspected:
- Consider dose reduction if clinically appropriate
- Consider switching to another statin (pravastatin or fluvastatin) that may have different side effect profiles
- Monitor liver function tests as elevated liver enzymes can occur in 0.7% of patients on atorvastatin 1
Clinical Evidence on Safety
A prospective study of 3,227 patients taking atorvastatin 40 mg daily found that only 1.2% reported gastrointestinal disturbances, and only 1.6% of all patients discontinued therapy due to any adverse effects 4. This suggests that while GI side effects can occur, they are generally well-tolerated and rarely lead to discontinuation.
Important Caveats
Paradoxical effects: In some specific patient populations, such as those with ulcerative colitis, atorvastatin may potentially worsen symptoms, including diarrhea 5
Drug interactions: Atorvastatin interactions with other medications may indirectly affect GI function. For example, when combined with cyclosporine or other immunosuppressants, there may be altered drug metabolism that could affect GI symptoms 3
Individual variation: Response to statins varies significantly between individuals, and some patients may be more sensitive to GI effects than others
Conclusion
While atorvastatin can cause diarrhea in a small percentage of patients, it is not specifically known for causing frequent stools as a primary side effect. If a patient develops this symptom while on atorvastatin, clinical evaluation should determine if the medication is the cause or if other factors are contributing to the symptoms.