METHEMOGLOBINEMIA INDUCED BY AN OVER-THE-COUNTER MEDICATION

OBJECTIVE: To report a case of methemoglobinemia induced by benzocaine and resorcinol (Vagisil) cream, an over-the-counter medication that w as used to treat diaper rash in a neonate. CASE REPORT: A 6-day-old, 3 350-g white boy was found to be cyanotic with blue mucous membranes on presentation. He had a diaper rash that was red and irritated, which his mother had treated with Vagisil cream. Methemoglobinemia secondary to absorption of benzocaine and resorcinol (1,3-benzenediol) from the Vagisil was diagnosed, with a methemoglobin level of 35% on admission (normal 0.4-1.5). Intravenous methylene blue 3 mg (1 mg/kg) was given ; the neonate's skin color returned to normal 45 minutes after the dos e. DISCUSSION: Methemoglobinemia is a condition in which hemoglobin is oxidized to the ferric form. Oxidized hemoglobin, methemoglobin, is i ncapable of reversibly binding oxygen at the physiologic partial oxyge n pressure. Main causes of methemoglobin formation are exposure to cer tain oxidizing agents and drugs, deficiency of one of the enzymes nece ssary for reduction of methemoglobin to hemoglobin, or the presence of an abnormal hemoglobin resistant to reduction. Clinical manifestation s of methemoglobinemia include diffuse slate-gray cyanosis with low ox ygen saturation in the absence of respiratory distress. A single intra venous dose of methylene blue 1-2 mg/kg is the treatment of choice. CO NCLUSIONS: Newborn infants are at increased risk for methemoglobinemia due to diminished enzyme systems required to reduce ferrihemoglobin t o ferrohemoglobin, as well as because fetal hemoglobin is more easily oxidized than is adult hemoglobin. It is important to recognize possib le drug reactions and educate parents on the potential risks of treatm ent with over-the-counter medications, especially in neonates.