1. ¹Instituto de Biomedicina de Sevilla, Servicio de Enfermedades Infecciosas, Hospitales Universitarios Virgen del Rocío, Seville, Spain
2. ²Servicio de Bioquímica Clínica, Hospitales Universitarios Virgen del Rocío, Seville, Spain
3. ³Servicio de Medicina Interna, Hospital Universitario Puerta del Mar, Cádiz, Spain
4. ⁴Servicio de Medicina Interna, Hospital de Jerez, Cádiz, Spain
5. for Grupo Andaluz para el Estudio de las Enfermedades Infecciosas.

Correspondence: L.F. Lopez-Cortes, (lflopez@telefonica.net)

Received 12 January 2008; Accepted 24 April 2008; Published online 2 July 2008.

Abstract

The effect of simultaneous plasma concentrations of pegylated interferon--2a (pegIFN--2a) and ribavirin (Rbv) on viral response has not been addressed to date. Hepatitis C virus (HCV)/human immunodeficiency virus (HIV)–coinfected patients received pegIFN--2a and Rbv under routine clinical care conditions. Plasma concentrations of the two drugs were measured using enzyme-linked immunosorbent assay and high-performance liquid chromatography after 2, 4, 8, and 12 weeks and at the end of the treatment period (24–48 weeks, according to HCV genotype and treatment duration). Large interindividual variability was observed in the plasma levels of both drugs. After multivariate analysis, only HCV genotype 3, low HCV-RNA levels, and pegIFN--2a exposure remained as independent factors associated with sustained viral response (SVR). The probability of attaining an SVR in HCV genotypes 1 and 4 was more than three to four times higher in patients with pegIFN--2a levels above the selected cutoff point. Early therapeutic drug monitoring of pegIFN--2a levels could be beneficial in improving current treatment outcomes.