Adherence to Pegylated Interferon/ribavirin Therapy for Hepatitis C and Early Treatment Response

It is well known that good adherence is an important contributor to successful treatment of many diseases.

In the case of chronic hepatitis C, suboptimal drug exposure due to physician-directed pegylated interferon and/or ribavirin dosage reductions -- typically done to manage side effects -- have been linked to decreased sustained virological response (SVR) rates, but there is less data about suboptimal drug exposure attributable to patients missing doses.

As described in the January 15, 2009 issue of Clinical Infectious Diseases, Vincent Lo Re and colleagues examined the relationship between adherence to interferon-based therapy and HCV suppression during the initial 12 weeks of treatment.

This cohort study included 188 chronic hepatitis C patients treated with pegylated interferon plus ribavirin. Adherence was calculated using pharmacy refill data. The primary outcome was decrease in HCV viral load at 12 weeks. Early virologic response (EVR) at week 12 was a secondary outcome. Subanalyses were performed among patients who received optimal weight-based dosages.

Results

The mean decrease in HCV RNA at 12 weeks was 0.66 log IU/mL greater for patients with 85% or better adherence than for those with less than 85% adherence (3.23 vs 2.57 log IU/mL; P = 0.04).

When patients who received a suboptimal ribavirin dosage were excluded, the decrease in viral load was 1 log IU/mL greater for patients with 85% or better adherence (3.32 vs 2.32 log IU/mL; P = 0.01).

Patients with 85% or better adherence were more likely to achieve early virological response than those with less than 85% adherence to pegylated interferon (73% vs 29%; P = 0.02) or ribavirin (73% vs 55%; P = 0.08).

"Adherence of > 85% to pegylated interferon and ribavirin treatment was associated with increased HCV suppression," the study authors concluded.

"Decreases in HCV load became greater when patients with > 85% adherence to their regimen continued to receive their recommended weight-based ribavirin dosage," they added.

Division of Infectious Diseases, Department of Medicine, Department of Biostatistics and Epidemiology and Center for Clinical Epidemiology and Biostatistics, and Center for Education and Research on Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA; Philadelphia Veterans Affairs Medical Center, Philadelphia, PA.

1/30/09

Reference
V Lo Re III, VK Amorosa, AR Localio, and others. Adherence to Hepatitis C Virus Therapy and Early Virologic Outcomes. Clinical Infectious Diseases 48(2): 186-193. January 15, 2009. (Abstract)..