Cefdinir is an extended-spectrum,
third-generation cephalosporin that may be used for treatment of acute
otitis media in patients allergic to
penicillin. When administered with
iron-containing products, including infant formulas,
cefdinir or one of its metabolites may bind to ferric
ions, forming a nonabsorbable complex that imparts a reddish color to the stool. We describe a 9-month-old infant with
failure to thrive and acute
otitis media who developed an erythematous maculopapular
rash during treatment with
amoxicillin-
clavulanate. His
antibiotic therapy was changed to
cefdinir. Five days into a 10-day course of
therapy, the infant's mother brought him to the pediatric clinic and reported the appearance of red stools. He had no associated gastrointestinal symptoms (
vomiting,
abdominal pain, or
diarrhea). His hematocrit and
hemoglobin level were normal, and Clostridium difficile
antigen studies and tests for species of Shigella, Salmonella, and Camphylobacter as well as ova and parasites were all negative.
Cefdinir was discontinued, and his stools returned to normal within 48 hours. Three weeks later, he again received
cefdinir for recurrent
otitis media. Red stools reappeared 48 hours later, were determined to be
guaiac negative, and resolved within hours of
drug discontinuation. During both occurrences of red stools, the infant had been breastfed and was receiving supplemental feedings with an
iron-containing infant formula. In the product labeling of
cefdinir, this adverse event is described as a consequence of the
drug-drug interaction; however, it is not listed in the
adverse drug reaction section of the labeling. As such, one may miss the association between
cefdinir and reddish stools when investigating this event as a potential adverse reaction to
cefdinir. When using the Naranjo
adverse drug reaction probability scale to assess causality in our patient's case, this
adverse drug reaction was determined as highly probable. As this infant had been breastfed, the use of a supplemental
iron-containing infant formula was not identified as a potential contributing factor until the second occurrence of red stools. Health care professionals should review the entire product labeling, including the
drug-drug interaction section, when investigating a potential
adverse drug reaction. With the recent approval of generic formulations of
cefdinir, clinicians should be aware of this
drug-drug interaction with
iron-containing products to prevent unnecessary alarm by parents and caregivers, as well as costly medical evaluations for gastrointestinal
bleeding.