Can Fluconazole Cause Blood in Stool?
Fluconazole does not directly cause blood in the stool as a recognized adverse effect. The most common gastrointestinal side effects of fluconazole are nausea and vomiting, not gastrointestinal bleeding 1.
Known Gastrointestinal Side Effects of Fluconazole
The established adverse effects profile of fluconazole includes:
- Gastrointestinal symptoms are the most frequent adverse effects, primarily consisting of nausea and vomiting 1
- These gastrointestinal effects occur in a minority of patients and are generally mild and transient 2, 3
- Ketoconazole (another azole) causes gastrointestinal symptoms more frequently (10-40% of patients) compared to fluconazole 1
Other Documented Adverse Effects
Beyond gastrointestinal upset, fluconazole's recognized side effects include:
- Hepatotoxicity: Asymptomatic transaminase elevations occur in 1-13% of patients, with rare cases of hepatitis and fatal hepatitis reported 1
- Dermatologic reactions: Skin rash, pruritus, and rare cases of Stevens-Johnson syndrome 1
- Alopecia: Hair loss in scalp and pubic areas 1
- Hematologic abnormalities: Rare reports exist, though thrombocytopenia and leukopenia are more commonly associated with itraconazole 1
Clinical Interpretation
If a patient on fluconazole presents with blood in the stool, alternative explanations should be investigated:
- Drug interactions: Fluconazole inhibits CYP2C9 and can increase warfarin levels, potentially causing bleeding complications including gastrointestinal bleeding 4
- Underlying conditions: The fungal infection being treated or the patient's immunocompromised state may be contributing factors
- Concurrent medications: Other drugs that affect coagulation or cause gastrointestinal irritation should be reviewed
The presence of blood in stool warrants immediate evaluation for other causes, as this is not an established side effect of fluconazole monotherapy 1.