Interaction between warfarin and molnupiravir in a patient with coronavirus disease 2019 infection

Area of Science:

• Pharmacology
• Infectious Diseases
• Internal Medicine

Background:

• Molnupiravir is an antiviral medication used for treating coronavirus disease 2019 (COVID-19).
• Warfarin is an oral anticoagulant requiring careful management due to potential drug interactions.
• Drug interactions with molnupiravir are not fully characterized, posing a risk in patients with comorbidities.

Observation:

• A case study documented a patient receiving both warfarin and molnupiravir for COVID-19 treatment.
• The patient experienced a significant increase in international normalized ratio (INR) to 3.80 after five days of molnupiravir therapy.
• This INR elevation occurred despite stable warfarin dosage and baseline INR prior to molnupiravir initiation.

Findings:

• The observed INR prolongation was attributed to a potential drug interaction between molnupiravir and warfarin.
• Other common factors influencing INR, including disease severity, cytokine storm, diet, liver function, and other medications, were ruled out.
• This suggests a direct interaction effect of molnupiravir on warfarin's anticoagulant activity.

Implications:

• Healthcare providers should exercise caution when prescribing molnupiravir to patients on warfarin therapy.
• Close monitoring of INR levels is crucial to detect and manage potential over-anticoagulation.
• Further research is warranted to elucidate the mechanism of this drug interaction and establish clinical guidelines.