Pharmacokinetic and pharmacodynamic considerations on the erythropoietin effect and adverse events of darbepoetin

Abstract

Introduction: In the TREAT and RED-HF trials, patients who received a high darbepoetin dose had an increased risk of adverse events. To find an explanation, the published literature was analyzed on the pharmacokinetics and pharmacodynamics of darbepoetin.

Areas covered: Based on the sigmoid E_max model, the concentration producing 50% of the maximum erythropoietin effect is reported as CE₅₀ = 0.41 ng/ml and the Hill coefficient as H = 3.0 for darbepoetin. Accordingly, a pharmacodynamics-based threshold concentration can be estimated with CE05 = 0.153 ng/ml producing 5% of E_max and a ceiling concentration with CE95 = 1.098 ng/ml producing 95% of E_max, respectively.

Expert opinion: Darbepoetin trough levels should not be less than the threshold concentration but peak levels above the ceiling concentration could be associated with an increased risk of adverse events. The time span associated with the concentration fluctuation between the ceiling and the threshold concentration is estimated with 236 h (= 2.84 times elimination half-life of 83 h) and shorter than the 336 h when dosing every other week. According to such time-dependent pharmacodynamics, a weekly dosing regimen might be more effective and associated with less adverse events than higher doses every other week in patients with suboptimal response to a normal darbepoetin dose.

Keywords:

• ceiling concentration
• darbepoetin
• Hill coefficient
• pharmacodynamics
• pharmacokinetics
• threshold concentration
• time-dependent action

Declaration of interest

F Keller received research funding from Amgen Co. within the TREAT trial and honoraria as well as meeting sponsoring from Roche Co. D Czock has received travel support, lecture honoraria and/or fees for review activities such as data monitoring boards from Sanofi-Aventis, Novartis and Bayer Vital GmbH, not related to the present study or to erythropoiesis stimulating drugs. The paper was presented as a poster at the ERA-EDTA meeting May 24 to 27 in Paris, 2012. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript other than those disclosed.