It has been suggested that alteration in the apparent oral bioavailability of propranolol taken with food may be due to a transient increase in QH. To investigate this hypothesis more closely, the time course of effect of a high-protein meal on QH was examined with the model compound ICG. Forty minutes postprandial, the mean increase in estimated QH was 69% above the control. QH was still elevated a mean of 36% at 100 min but by 280 min had decreased to a value that did not differ from control. Computer simulations were performed to predict the magnitude of change in the apparent oral bioavailability of propranolol that would be expected based on the observed QH changes. These simulations suggest that simple changes in QH alone cannot account for the increase in apparent oral bioavailability when propranolol is taken with food.
Dose proportionality of racemic bisoprolol and the stereoselectivity of its enantiomers were studied after single oral dosing of 5 to 40 mg of bisoprolol hemifumarate in eight healthy male volunteers in an open-label, randomized, four-way cross-over trial. There were dose-proportional increases in mean peak plasma concentration (Cmax) and area under the plasma concentration versus time curve (AUC) values for the racemate and the individual enantiomers. No statistically significant differences were detected between the mean half life (t 1/2), Cmax, and time to reach Cmax (tmax) of the R- and S-isomers at each of the four dose levels studied. These findings support dose proportionality and absence of stereoselective pharmacokinetics for bisoprolol in the dose range studied.
The pharmacokinetics of cefixime were compared in 12 young and 12 elderly subjects receiving 400 mg once-a-day for five days. Mean peak serum concentrations (Cmax) on days one and five in the elderly (4.90 and 5.68 mg/l) were comparable (P greater than 0.05) to those in the young subjects (3.88 and 4.74 mg/l). Serum area under the curve (AUC) values on days one and five in the elderly (41.0 and 49.5 mg.h/l) were higher (P less than 0.05) than those in young subjects (28.6 and 34.9 mg.h/l). In addition, the elimination half-life, mean residence time, average concentration, minimal concentration and renal clearance (Clr) values were significantly higher (P less than 0.05) in the elderly. A significant linear correlation (P less than 0.05) was found between the Clr of cefixime (total and unbound) and creatinine clearance. The urinary recovery (Ae0----24) and protein binding of cefixime on days one and five was similar in the elderly and young. Overall, there is no need for any dosage adjustment of the drug in the elderly.
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