Decreased INR after acenocoumarol, ombitasvir/paritaprevir/ritonavir and dasabuvir co‐administration

Summary What is known and objective Limited data are available on co‐administration of acenocoumarol with direct‐acting antiviral agents for chronic hepatitis C virus infection. Case summary We report a case of a patient who required a significant increase in acenocoumarol weekly dose probably due to an interaction with ombitasvir/paritaprevir/ritonavir and/or dasabuvir. A causality assessment of the drug–drug interaction leading to a reduced INR was conducted according to the Naranjo algorithm. A score of 6 suggested that the adverse drug reaction was probable. What is new and conclusion Because of possible INR abnormalities during the concomitant use of acenocoumarol, ombitasvir/paritaprevir/ritonavir and dasabuvir, clinicians should closely monitor INR values.