Pharmacokinetics of alphaIFN-2b in chronic hepatitis C virus patients undergoing chronic hemodialysis or with normal renal function: clinical implications.

Abstract

In this prospective controlled study, the pharmacokinetic profiles of alpha-interferon 2b (alphaIFN-2b) were determined by the enzyme-linked immunosorbent assay method in hepatitis C virus-positive (HCV+) dialysis and nonuremic patients, after a single subcutaneous injection of 3 million units. Ten HCV+/RNA+ patients (group A) with a normal renal function (mean serum creatinine: 1.03 +/- 0.26 [SD] mg/dl) and 10 HCV+/RNA+ patients undergoing chronic hemodialysis (group B) were included. The pharmacokinetic profiles of alphaIFN were determined after the very first subcutaneous injection of the drug. Plasma alphaIFN concentrations were determined before the injection and then 1, 2, 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, and 36 h after the injection. They were assessed by means of an enzyme-linked immunosorbent assay test. Patients from both groups had a similar body surface area. It was found that in group B: (1) the mean maximum (SD) serum alphaIFN concentration (Cmax) was significantly higher (52 +/- 12 pg/ml) than in group A (39 +/- 12 pg/ml; P = 0.03); (2) the time at which Cmax occurred (Tmax) was significantly higher (10 +/- 3 h) than in group A (7.5 +/- 2 h; P = 0.05); (3) the observed area under the plasma alphaIFN concentration-time curve was about twice as much, i.e., 936 +/- 212 pg x h/ml, as that for group A (485 +/- 184 pg x h/ml; P < 0.0001); and (4) the alphaIFN half-life was significantly longer (9.6 +/- 2.9 h) than in group A (5.3 +/- 1.3 h). As early as 24 h after the alphaIFN injection was given, the drug was no longer detectable in nonuremic patients' sera, whereas it could be detected up to the next injection in all of the dialysis patients' sera. When trough levels of alphaIFN were measured just before the 10th injection, they were always below the threshold level in the 10 patients from group A, i.e., 4.1 pg/ml, whereas in group B they were measurable for four of nine patients (P = 0.05) and ranged between 5.8 and 36.1 pg/ml. Severe neurologic side effects were observed only in group B, i.e., in three patients. Hemoglobin levels did significantly decrease but only in group B patients, and this was significantly correlated with the Cmax (r = 0.67; P = 0.03). This is the first controlled study to demonstrate that the clearance of alphaIFN is about twice as low in dialysis patients as in nonuremic patients. These results might be of relevance when deciding the optimal alphaIFN therapy scheme for HCV+ patients, either with normal renal function or undergoing chronic hemodialysis.