A number of drugs and foods can change the effect of warfarin.
Check for drug Interactions
Starting or stopping medication
When a patient changes their medication it is important to consider the effect it may have on their warfarin control.
If a patient starts new medication that can influence warfarin control you should check the INR 3 to 4 days after starting treatment.
It is also important to remember that warfarin control may alter when medication is stopped.