The plasma disposition of the enantiomers of ibuprofen has been investigated following the oral administration of the racemic drug (400 mg) to 24 healthy male volunteers. The plasma elimination of (R)-ibuprofen was found to be more rapid than that of the S-enantiomer [plasma half-life: (R) 2.03 h; (S) 3.05 h; 2P less than 0.001], resulting in a progressive enrichment in the plasma content of this isomer, some 64% of the total area under the plasma concentration time curves (AUC) being due to the pharmacologically active enantiomer. The influence of dose on the pharmacokinetic characteristics of the enantiomers of ibuprofen, over the range 200-800 mg, was investigated in three subjects. Examination of dose-normalized AUC values and oral clearance indicate the dose dependence of (R)-ibuprofen disposition.
A simple and rapid (extractionless) high-performance liquid chromatographic method with UV detection at 230 nm was developed for the determination of lansoprazole in biological fluids and pharmaceutical dosage. Niflumic acid was added as internal standard. The separation was performed at ambient temperature on a C18 Spherisorb column with acetonitrile + 0.1 M sodium acetate (40:60, v/v, pH 7) as mobile phase. The retention time was 5.2 min for niflumic acid and 6.7 min for lansoprazole. The detection limit was 20 ng/ml using a 100 microl loop. The method was successfully applied to a pharmacokinetic study of lansoprazole in humans.
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