Information on Potential Vitamin K Interaction with Warfarin

Pfizer would like to inform healthcare professionals that the recent formulation change for Centrum Silver to include vitamin K may potentially decrease the anticoagulant effects of anticoagulant drugs such as warfarin, especially in elderly patients, therefore causing potential fluctuations in their International Normalised Ratio (INR) readings. This was evidenced by a locally reported case. Such an adverse event is noted to be rare. The daily dose of vitamin K at 25 mcg in Centrum Silver is lower than that found in common vegetables. Healthcare professionals are advised to remind elderly patients taking warfarin of the potential interaction of their medication with supplements containing vitamin K and to monitor the INR of patients taking warfarin closely if they are new or existing Centrum product users. Please refer to the Dear Healthcare Professional Letter for more details.