The pharmacokinetics of oral ranitidine were studied in 9 patients (ages 9.
9 to 19.6 years) with cystic fibrosis (CF). patients were evaluated at stea
dy-state conditions, and the mean maximum serum concentration (C-max) was 8
45.7 +/- 448.2 ng/mL. To adjust for the variable drug dosing used among stu
dy patients both C-max and area under the concentration curve (AUC) were st
andardized to dose (C-maxST and AUC(ST), respectively) and were 217.9 +/- 8
7.9 ng/ml and 1038.0 +/- 242.2 ng/mL . h. The elimination half-life (t(1/2)
) was 2.7 +/- 1.4 hours, and the apparent steady-state volume of distributi
on (Vd(SS)) was 4.6 +/- 1.7 L/kg. The plasma clearance was 1.022 +/- 0.290
L/kg/h. The Vd(SS) in this study was greater than that previously reported
in children with peptic ulcer disease. Statistically significant relationsh
ips between pharmacokinetic parameters and measures of disease severity wer
e not observed in the study population. The pharmacokinetics of ranitidine
in children and adolescents with CF may differ from those in children and a
dolescents without CF. (C) 1999 the American College of Clinical Pharmacolo
gy.