Lack of adverse side effects of oral ferrous sulfate therapy in 1-year-old infants.

An evaluation was made of 278 healthy-appearing 1-year-old infants who were tested for iron deficiency to determine the relative frequency of adverse side effects attributable to oral iron treatment. After obtaining parental informed consent, laboratory tests of iron status were performed on venous blood and infants with hemoglobin level greater than 10.5 g/dL were randomly chosen to receive 1.2 mL of ferrous sulfate (FeSO4) drops (about 3 mg of iron per kilogram per day) or equal volume of placebo for 3 months. After 3 months of treatment, infants were to return to the clinic for repeat blood testing, compliance estimation, and evaluation for possible adverse side effects. There was no significant difference (P greater than .50) in the frequency of vomiting, diarrhea, or fussiness in iron-treated infants (6%) compared with placebo-treated infants (9%). Constipation was slightly more frequently reported (P = .03) in placebo-treated infants (9%) than in iron-treated infants (1%). Compliance with therapy was confirmed in 179 completely evaluated infants by the lack of remaining medication at 3 months, the higher incidence (P less than .0001) of dark stools reported among iron-treated infants, and the changes in laboratory tests of iron status. No parents reported dark stools as an adverse effect of therapy. It is concluded that once daily, moderate-dose FeSO4 therapy given to fasting 1-year-old infants results in no more gastrointestinal side effects than placebo therapy.