RANITIDINE PHARMACOKINETICS IN NEWBORN-INFANTS

Few data are available for ranitidine pharmacokinetics in the first fe w days of life. Twenty seven newborn infants were treated with intrave nous ranitidine because they were vomiting blood, although they had a negative Apt's test. Each infant provided two blood samples at randoml y selected times 30-360 minutes after a 2.4 mg/kg intravenous bolus of ranitidine. A single exponential equation for the concentration-time graph was fitted to the mean serum concentrations at,different times. From this model the following mean (SD) measurements were derived: eli mination half life, 207.1 (19.1) minutes; total volume of distribution , 1.52 (0.91) l/kg; and total plasma clearance, 5.02 (0.46) ml/kg/min. Assuming that these measurements do not change with different adminis tered doses, regimens can be derived to assist in planning ranitidine treatment in newborn infants.