Warfarin-High INR

High international normalised ratio ( INR )- Consider aspects which may have caused INR to be out of range and level of INR

Any medication change ? antibiotic , amiodarone Missed dose or taken too much ? Any intercurrent illness ? gastroenteritisfever , onset of jaundice , weight loss , ? worsening renal function Excessive alcohol consumption ? herbal remedies OTC meds eg cranberry juice , miconazole gel Smoking cessation ( can ↑ the effect of warfarin )

Key drug interactions enhancing the effect of warfarin ( CKS )

alcohol-Advice to avoid binge drinking. Heavy drinkers who cannot abstain should not take warfarin. alcohol acts as both enzyme inhibitor and inducer

amiodarone -Amiodarone and warfarin potentiate the effect of warfarin and prolongs the INR -increased risk of bleeding . Interaction may persist for a month or more after stopping amiodarone

Antibiotics- check INR 4-7 days after any antibiotic use Co-trimoxazole consider if trimethoprim could be used or reduce the warfarin dose Metronidazole - reduce warfarin dose as necessary

antidepressants-avoid SSRI and SNRI if possible ( antiplatelet effect ) consider trazodone instead

Azoles- measure INR 4-7 days after using fluconazole , miconazole and voriconazole (adjust the dose based on INR )...