Paritaprevir/ritonavir/ombitasvir+dasabuvir plus ribavirin therapy and inhibition of the anticoagulant effect of warfarin: a case report.
OBJECTIVE
Paritaprevir/ritonavir/ombitasvir+dasabuvir (PrOD) is a direct-acting antiviral (DAA) approved for the treatment of chronic hepatitis C virus. We report on a probable interaction between PrOD with ribavirin and warfarin.


METHODS
Two weeks after the start of PrOD with ribavirin, the patient's international normalized ratio (INR) became subtherapeutic. Eleven weeks into therapy and following a 125% total increase in the weekly warfarin dose, therapeutic INR was achieved. Thirteen days after DAA therapy was completed and discontinued, the patient's INR became critically supratherapeutic.


CONCLUSIONS
Patients on PrOD plus ribavirin with warfarin should have INR followed closely upon initiation and discontinuation of therapy due to a probable drug interaction.
PGY2 Pharmacy Resident, Ambulatory Care, VA Maine Healthcare System, Augusta, ME, USA.
G M
http://orcid.org/0000-0001-7749-0683
GM
Puglisi
Clinical Pharmacy Specialist, Pharmacy Service, VA Maine Healthcare System, Augusta, ME, USA.
S M
SM
Smith
Gastroenterology Section, Medical Service, VA Maine Healthcare System, Augusta, ME, USA.
R D
RD
Jankovich
Department of Pharmaceutical Sciences, St. John's University, Queens, NY, USA.
C R
CR
Ashby
Clinical Pharmacy Specialist, Pharmacy Service, VA North Texas Health Care System, Dallas, TX, USA.
T Z
TZ
Jodlowski
D015081:2-Naphthylamine; D000813:Anilides / Q000009:adverse effects* / Q000627:therapeutic use; D000925:Anticoagulants / Q000627:therapeutic use*; D000998:Antiviral Agents / Q000009:adverse effects / Q000627:therapeutic use; D002219:Carbamates / Q000009:adverse effects* / Q000627:therapeutic use; D003521:Cyclopropanes; D004347:Drug Interactions; D004359:Drug Therapy, Combination / Q000009:adverse effects; D019698:Hepatitis C, Chronic / Q000188:drug therapy; D006801:Humans; D047029:Lactams, Macrocyclic; D047028:Macrocyclic Compounds / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011392:Proline / Q000031:analogs & derivatives; D012254:Ribavirin / Q000627:therapeutic use*; D019438:Ritonavir / Q000009:adverse effects* / Q000627:therapeutic use; D013449:Sulfonamides / Q000009:adverse effects* / Q000627:therapeutic use; D014498:Uracil / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D014633:Valine; D014859:Warfarin / Q000627:therapeutic use*
D000813:Anilides; D000925:Anticoagulants; D000998:Antiviral Agents; D002219:Carbamates; D003521:Cyclopropanes; D047029:Lactams, Macrocyclic; D047028:Macrocyclic Compounds; D013449:Sulfonamides; C586094:ombitasvir; D012254:Ribavirin; D014498:Uracil; D014859:Warfarin; D011392:Proline; D015081:2-Naphthylamine; C588260:dasabuvir; D014633:Valine; D019438:Ritonavir; C585405:paritaprevir
anticoagulation; drug interaction; paritaprevir/ritonavir/ombitasvir+dasabuvir; ribavirin; vitamin K antagonist; warfarin