The pharmacokinetics of etanercept in patients with end-stage renal disease on haemodialysis

Inflammation is strongly associated with malnutrition and cardiovascular risk in patients with chronic renal failure on haemodialysis (HD). The acute-phase inflammatory response, defined by the increased synthesis of positive acute-phase proteins, is stimulated by the production of such cytokines as interleukin 6 (IL-6), interleukin 1 (IL-1) and tumour necrosis factor-alpha TNF-alpha The availability of cytokine antagonists allows testing of the hypothesis that suppression of inflammation reverses the malnutrition-inflammation syndrome in HD patients. Etanercept is a soluble TNF-alpha receptor fusion protein used to suppress inflammation in rheumatoid and psoriatic arthritis. Its metabolism in HD patients is unknown. In a study designed to test the safety and pharmacokinetics of etanercept in HD patients, etanercept was administered to six HD patients with albumin levels above 4.2 g dL(-1) and C-reactive protein levels <5 mg L(-1) (five men, one woman, age range 34-59 years). Etanercept (25 mg) was administered subcutaneously twice weekly immediately after dialysis for 13-16 weeks. Etanercept concentrations were measured pre- and post-dialysis by ELISA. Concentrations were compared graphically to assess whether, firstly, dialysis affects etanercept apparent clearance and, secondly, etanercept kinetics were similar between HD patients and the more extensively studied psoriasis population with normal renal function (PS). The second stage examined model-based parameter predictions of the terminal elimination rate constant (k) for HD patients. Steady-state etanercept levels were comparable between HD and PS patients. Treatment with HD had no effect on etanercept levels. When etanercept was discontinued, the terminal rate constant for HD patients was not significantly different from that observed in PS patients. No adverse effects were noted during the 3-month treatment phase and subsequent 6-month follow-up. Albumin and C-reactive protein levels did not change in these non-inflamed patients during the study period. The pharmacokinetics of etanercept in patients with chronic renal failure on HD are similar to patients with normal renal function. It is, therefore, feasible to administer etanercept to HD patients without adjusting the dose.