Different recombinant human erythropoietin products have been developed. Although they appear to have similar pharmacokinetics and function, these have not been directly compared. This randomized, double-blind, four-period crossover study compared the pharmacokinetics and pharmacodynamics of intravenous and subcutaneous epoetin alfa and epoetin beta in 18 normal male volunteers. As a control, three subjects received placebo treatment. After intravenous administration, the steady-state volume of distribution and beta-phase volume of distribution of epoetin beta were 7.7% and 16.9% larger than for epoetin alfa (p less than 0.05). The terminal elimination half-life after intravenous administration of epoetin beta was 20% longer than the terminal elimination half-life of epoetin alfa. After subcutaneous administration there was a delayed drug absorption with epoetin beta compared with epoetin alfa (p less than 0.05). There was a small but significantly greater absolute reticulocyte response after subcutaneous epoetin beta compared with subcutaneous epoetin alfa. The findings support differences in the pharmacokinetics and function of epoetin alfa and beta that are possibly caused by differences in their glycosylation.

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Aims Various mathematical models have been developed to estimate glomerular filtration rate (GFR) incorporating variables such as age, gender, height, weight, serum creatinine, and body surface area (BSA). Because adjustments in drug dosing are often based on estimated values of renal function, it is important to define which, if any, of the available models, is appropriate for a specific patient population. A study was undertaken to determine the bias and precision of four mathematical models to estimate GFR in renal allograft recipients. Methods A retrospective review of 142 stable renal allograft patients, using iohexol clearance as a determinant of GFR, was performed. Renal allograft recipients followed in an outpatient clinic setting underwent iohexol clearance studies as part of clinical monitoring in the post-transplant period. Measured GFR values were compared with four mathematical models used to estimate GFR: the CockcroftGault equation, the Jelliffe equation, the Walser equation, and the Mawer equation. Bias and precision were determined for each model as the mean squared error and the mean squared error, respectively. Results Patients had a mean age of 44±13 years, 92 were male, and 50 were female. The serum creatinine concentration was 176.8±88.4 mmol l −1 (mean±s.d.).The mean time post-transplant was 5.1±5.0 years and 38% of patients had insulinrequiring diabetes mellitus. The bias and precision results for the Jelliffe, Walser, Cockcroft-Gault, and Mawer models were: −3 and 414; −5 and 381; 16 and 688; and 23 and 1084, respectively. Conclusions The Jelliffe and Walser equations gave the least biased and most precise estimations of GFR when compared with iohexol-derived measures in patients with renal allografts.