Pharmacokinetics of ranitidine in critically ill infants.

The pharmacokinetic parameters of ranitidine were studied following administration of a single intravenous dose in 9 critically ill infants. Ranitidine disposition was best described by a biphasic elimination curve. For 8 patients, the mean values for T1/2, apparent volume of distribution, and total body clearance were 2.09 h, 1.61 l/kg, and 13.93 ml/min/kg, respectively. Based on simulated steady-state concentration profiles, a dose of 0.7 mg/kg administered intravenously every 6 h should maintain serum levels above 40 ng/ml for 4.7 h of the dosing interval with a wide degree of variability.