The pharmacokinetic properties of fluconazole were studied in more than 100 pediatric patients, including 12 premature neonates. The volume of distribution and the rate of elimination differed significantly from the values reported for adults. The volume of distribution varied with age, being greatest during the neonatal period (1.18 to 2.25 l/kg) and decreasing by young adulthood to a value similar to that reported for adults (0.7 l/kg). With the exception of neonates, fluconazole clearance was generally more rapid in children than in adults, with a mean plasma elimination half-life of just over 20 h for all pediatric age groups. In neonates, fluconazole was eliminated slowly, with a mean elimination half-life of 88.6 h at birth, 67.5 h approximately one week later and 55.2 approximately two weeks after birth. Fluconazole appeared to be well absorbed from the gastrointestinal tract. These pharmacokinetic results, taken in conjunction with the corresponding data for adults, provide a sound basis for establishing appropriate fluconazole dosage recommendations for pediatric patients.

1 A combined pharmacokinetic and pharmacodynamic model has been used to analyze the relationship between electrocardiographic (ECG) and systolic time intervals (STI) and changes in plasma concentration of quinidine after oral and i.v. doses in ten normal subjects. 2 The major effects of quinidine were on cardiac repolarization. Contrary to previous descriptions, we found no important change in the U wave, but the T wave was split into two peaks. The amplitude of these two peaks (T and T') was reduced, and the QT' peak and QT intervals were prolonged. The QT peak interval and systolic intervals did not change appreciably. There were small increases in the PQ and QRS intervals. 3 The effect of quinidine on the QT interval could be explained by a linear pharmacodynamic model. The equilibration between plasma and effect site had a half‐time of 8 min. The slope of the pharmacodynamic model was 20.3 ms . mg 1(‐1) after i.v. dosing and 33.5 ms . mg 1(‐1) after oral dosing. 4 The difference in effect model slopes suggests pharmacologically active metabolites of quinidine are formed during absorption from the gut. 5 The total effect of a single oral dose of quinidine appears to be the same as the same dose given intravenously, even though only 70% of the oral dose reaches the systemic circulation as quinidine.

Eight healthy young and nine healthy elderly volunteers received 10 mg morphine sulphate as an intravenous infusion, an oral solution and a slow-release tablet (MST Continus, Napp Laboratories) on three separate occasions. Pharmacokinetic profiles of morphine base were measured over a 24-h period using 13 sampling times. The elderly group showed decreased morphine clearance with a trend to a smaller volume of distribution. They achieved higher maximum plasma concentrations (Cmax) after both oral formulations and had larger areas under the plasma concentration-time curves. The times to reach maximum concentrations were the same in both groups for all formulations.

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Parameters describing disposition and absolute oral bioavailability of quinidine were determined in ten normal male volunteers using a specific assay. Various models were compared for their ability to describe the experimental data. An intravenous quinidine gluconate and an oral quinidine sulfate solution were administered (3.74 mg/kg quinidine base). In three subjects the intravenous and oral studies were repeated. One-, two-, and three-compartment models with zero and first-order input were fitted to the plasma concentrations. The selection of the best model was made by the Akaike information criterion and by eye. After intravenous administration, plasma concentration-time curves could be adequately described by a two-compartment model. Mean disposition constants (+/- SD) were obtained from individualized fits (V1: 0.398 +/- 0.336 LITER/KG, Vdarea: 2.53 +/- 0.72 liter/kg, alpha: 0.316 +/- 0.294 min -1, beta: 0.00204 +/- 0.00262 min -1, k2: 0.0305 +/- 0.0101 min -1). A clearance of 4.9 +/- 1.5 ml/min/kg was observed. After oral administration, three-compartment models were needed to describe the observed data in some cases. Absorption was in most cases best described by a zero-order rather than by a first-order process. The time to peak concentration varied from 23 to 121 min, the lag time was always less than 3 min, and the mean elimination rate constant was 0.00171 min -1. The mean oral bioavailability of quinidine was 0.70 +/- 0.17.