Population pharmacokinetics of ibuprofen enantiomers in very premature neonates.

The objective of the present study was to evaluate the pharmacokinetic parameters for both S- and R-ibuprofen enantiomers in very premature neonates (gestational age strictly inferior to 28 weeks) and possible relationships between the pharmacokinetic parameters and various covariates. Newborns were randomized to receive ibuprofen or placebo for the prophylactic treatment of patent ductus arteriosus (PDA) at an initial dose of 10 mg/kg ibuprofen within 6 hours after birth, followed by two 5-mg/kg doses at 24-hour intervals (n = 52). If a PDA was still present afterwards, a curative course of ibuprofen using the same dosage regimen was administered (n = 10). A sparse sampling strategy was used because only 2 samples were collected after the third prophylactic injection and 1 after the third curative injection. A model including the chiral transformation of R- to S-ibuprofen was fitted to the concentration-time data using a population approach (NONMEM). R- and S-ibuprofen t(1/2) were about 10 hours and 25.5 hours, respectively. After prophylactic treatment, the mean clearance of R-ibuprofen (CLR = 12.7 mL/h) was about 2.5-fold higher than for S-ibuprofen (CLS = 5.0 mL/h). In addition, clearance of R- and S-ibuprofen increased significantly with gestational age. The mean estimation of R-ibuprofen clearance was found to be higher than for S-ibuprofen, and the clearance of both enantiomers increased with gestational age. This should be considered to assess pharmacokinetic-pharmacodynamic relationships of ibuprofen in premature neonates and subsequently to understand and refine the use of ibuprofen in managing PDA either as a prophylactic or curative treatment.

Oral bioavailability of gatifloxacin in healthy volunteers under fasting and fed conditions.

The effect of food on the pharmacokinetics of gatifloxacin given as a single oral dose of 400 mg under fasting and fed conditions was determined in 18 healthy male volunteers in an open, two-way, randomised cross-over study. Concomitant food intake did not significantly alter the peak plasma concentrations (C(max)) or the area under the plasma concentration-time curve (AUC) of gatifloxacin. The mean C(max) levels under fasting and fed conditions were 3.5 and 3.2 mg/l, respectively, after the 400-mg single dose of gatifloxacin. The corresponding mean AUC data were 32.8 mg x h/l (fasted) and 30.5 mg x h/l (fed). Moreover, the rate of absorption was not affected by food intake. The median T(max) value was 2 h in both treatment periods. No clinically relevant adverse effects or changes in clinical laboratory test results, ECGs or physical examinations were observed. The results of this study indicate that gatifloxacin given as a single 400-mg oral dose was well tolerated in the presence or absence of food. Concomitant administration of a continental breakfast with a caloric content of 1,050 kcal had no effect on the bioavailability of gatifloxacin. It is suggested that gatifloxacin can be given without regard to meals.

Multiple-dose pharmacokinetics and excretion balance of gatifloxacin, a new fluoroquinolone antibiotic, following oral administration to healthy Caucasian volunteers.

The multiple-dose pharmacokinetics and excretion balance of gatifloxacin were evaluated in 42 healthy Caucasian volunteers. Following multiple oral doses of 400 and 600 mg, the pharmacokinetics of gatifloxacin were similar on days 1 and 15, suggesting no therapeutically relevant time-dependent changes in the pharmacokinetics of gatifloxacin at the doses and duration of dosing studied. Gatifloxacin was rapidly absorbed and a favourable elimination half-life of 7-8 h was evaluated. Saliva concentrations were similar to plasma concentrations. The main route of excretion is the urine. After a single dose of 400 mg of gatifloxacin, the recovery in urine was 83% and 5.2% in faeces. Following multiple doses of 400 or 600 mg, the renal excretion was 80 and 77%, respectively. The drug was well tolerated.