Pharmacokinetic evaluation of cimetidine in newborn infants

The pharmacokinetics of cimetidine were studied in three newborn infants with reflux esophagitis or stress ulcer. One infant was given 5 mg/kg intravenously (IV), one was given 10 mg/kg IV, and one was given 10 mg orally. Serum concentrations 30 minutes after administration were 1.2 μg/ml, 5 μg/ml, and 4.2 μg/ml, respectively. Concentrations greater than 0.5 μg/ml were measured 1, 6, and 9 hours, respectively, after administration. The half-life of the drug ranged from 1.10 to 2.18 hours. These preliminary data suggest that a dose of 5 to 7 mg/kg would effectively suppress gastric acid secretion in neonates.