From the FDA Drug Label
There have been reports of reddish stools in patients receiving cefdinir. In many cases, patients were also receiving iron-containing products The reddish color is due to the formation of a nonabsorbable complex between cefdinir or its breakdown products and iron in the gastrointestinal tract.
Cefdinir (Omnicef) may cause rust-colored stools, due to the formation of a complex between the drug or its breakdown products and iron in the gastrointestinal tract, especially in patients also receiving iron-containing products 1.
From the Research
Yes, cefdinir can cause rust-colored stools, as evidenced by the most recent study in 2023 2, which highlights this interaction as a benign but underreported adverse drug reaction. This effect is typically not a cause for concern and occurs because cefdinir can interact with iron in the diet or iron supplements, forming a non-absorbable complex that appears as a rust-colored pigment in the stool. The discoloration is more common in children but can occur in patients of any age, and it is temporary, resolving once the medication is completed. It's crucial to distinguish this harmless discoloration from blood in the stool, which would be a more serious concern. Key points to consider include:
- The interaction between cefdinir and iron-containing products can lead to red stools, as noted in several studies 3, 4, 5, 6.
- The effect is reversible upon discontinuation of cefdinir, as observed in case reports 2, 5.
- Awareness of this side effect can prevent unnecessary anxiety, medical evaluations, and economic burden, as emphasized in recent literature 2. If you're taking cefdinir (typically dosed at 300 mg twice daily for adults or 14 mg/kg/day divided twice daily for children, for 5-10 days depending on the infection) and notice rust-colored stools, you can continue the medication as prescribed unless instructed otherwise by your healthcare provider. However, if you experience other concerning symptoms like severe abdominal pain, persistent diarrhea, or what appears to be actual blood in the stool, you should contact your healthcare provider promptly.