The MHRA advice, published in its latest Drug Safety Update, follows a Europe-wide review of the use of concomitant vitamin K antagonists (eg, warfarin) and direct-acting antivirals for hepatitis C, which reported that changes in liver function secondary to treatment with hepatitis C antivirals may affect the efficacy of vitamin K antagonists resulting in fluctutations in INR values.
The MHRA states that the benefits of treatment with direct-acting antivirals for chronic hepatitis C continue to outweigh the risks of an interaction with vitamin K antagonists. However, INR should be monitored closely in patients co-prescribed these medicines and anticoagulant therapy adjusted if necessary.
Patients should be advised to inform their doctor or pharmacist if they are taking warfarin or other similar medicines and are prescribed direct-acting antivirals. Those who are taking a vitamin K antagonist should be informed that they may need more regular blood tests during treatment for hepatitis C.
Direct-acting antivirals for the treatment of chronic hepatitis C include: daclatasvir (Daklinza), dasabuvir (Exviera), ombitasvir/paritaprevir/ritonavir (Viekirax), sofosbuvir (Sovaldi), sofosbuvir/ledipasvir (Harvoni), sofosbuvir/velpatasvir (Epclusa) and simeprevir (Olysio).