Co-morbid diseases often present in a substantial proportion of patients with chronic hepatitis C (CHC) and require drugs to treat and control. Grazoprevir/elbavir is metabolized by cytochrome P-450 enzyme of liver. Drug-drug interactions (DDIs) are important issue before commencing direct acting antiviral agents (DAA) treatment for CHC patients. Few studies from Western countries reported that the percentages of DDIs of grazoprevir/elbasvir are limited.In Asia, real-world analysis of DDIs of grazoprevir/elbasvir is lacking and needs to be clarified.

This is a multi-center, retrospective study. Five hospitals in Taiwan and 400 patients Patients treated with grazoprevir/elbasvir during August 2017 to July 2018 are candidates of study subjects. All the required study information will be recorded with detailed chart review.

DDI will be evaluated by HEP Drug Interactions (www.hep-druginteractions.org) assessment of comidications: Category 0: Classification not possible due to lack of information; Category 1: No clinical interaction possible; Category 2: May require dose adjustment/closer monitoring; Category 3: Coadministration not recommended or contraindicated.

The assessment of DDI will be evaluated and recorded according to the suggested categories, the number of patients at risk for a clinically relevant DDI, and the ratio of patients with at least one predicted DDI between medication of grazoprevir/elbasvir will be calculated.

Inclusion Criteria:

• Patients treated with grazoprevir/elbasvir are candidates of study subjects.

Exclusion Criteria:

• none

Patients infected with genotype 1 or 4 hepatitis C virus and treated with elbasvir/grazoprevir during August 2017 to July 2018 in Taiwan.