Pharmacokinetics of ranitidine in preterm and term neonates with gastroesophageal reflux.

BACKGROUND: The aim of this study was to determine the effect of gestational age on pharmacokinetics of ranitidine in newborns with gastroesophageal reflux. METHODS: A prospective, descriptive and pharmacokinetic study was carried out in 30 pre-term and 20 full-term babies. 3 mg/kg of ranitidine was administered intravenously to all the babies and at 0.25, 0.5, 1, 2, 4, and 8 h following the administration, samples of blood were drawn to assess ranitidine levels using high performance liquid chromatographic technique. RESULTS: Pharmacokinetics of ranitidine had a bi-exponential behavior with a half-life elimination of (t1/2el) 2.79 h, area under curve (AUC) of 1688 ng/mL, volume of distribution (Vd) of 1.44 L/kg, and clearance (Cl) of 5.9 L/kg/h. The median plasmatic concentration in pre-terms was 1113 ng/mL and 280 ng/mL in full-terms. Vd, t1/2 and Cl presented high values in preterm although the correlation of Cl with glomerular filtration in term newborns was better. CONCLUSIONS: Plasma levels of ranitidine depend on the gestational age of the newborns. However, the possible relationship between after-birth age and pharmacokinetics of the neonates as their internal organs get matured without minding their gestational background.

Effect of severity disease on the pharmacokinetics of cefuroxime in children with multiple organ system failure.

The aim of the present study was to investigate if the severity of illness affected the pharmacokinetics of cefuroxime in 11 children diagnosed with multiple organ system failure. The patients were assigned to a severely ill group (group 1), a very severely ill group (group 2), or a control group (group 0). Blood samples were taken and cefuroxime concentrations were measured in plasma by HPLC after the first intravenous infusion of 100 mg of cefuroxime per kg of body weight. The pharmacokinetic profile of cefuroxime exhibited both one and two compartmental distribution. Statistically significant differences between the pharmacokinetic parameters of the severe (group 1) and the very severe patients (group 2) were found, and significant differences (p<0.05) in the pharmacokinetic parameters between groups 1 and 2 vs. the control group were observed for most of the parameters analyzed. However, there was no statistical difference in clearance between group 1 and the control group. The data indicate that the pharmacokinetic differences determined by severity of disease are useful for establishing an individualized regimen dosage in children with multiple organ system failure.