Complementary and Alternative Medicines (Part 1)

By: Alere Staff
Publication Date: Tue, 11/01/2011

A study published in Pharmacotherapy, Sept. 2007 evaluated 171 adults and their increased risk of elevated INRs and bleeding risk. Alternative medicines have become one of the fastest growing challenges facing anticoagulation clinics. Patients remain rather freewheeling with their choices of alternative medicines and communication about their use is often lacking. Alternative medicines are also referred to as: holistic and natural medicines, dietary and herbal supplements. The prospective, longitudinal study relied on patients (on warfarin for at least 4 months) filling out weekly studies over the 16 week evaluation period.1 The survey consisted of questions on warfarin use, side effects and use of complementary and alternative medicines (CAM). 93% of the patients completed at least 15 weeks of the 16 week program.1

Forty-six percent of study patients reported using one or more alternative medicine during the study. Forty-four percent of patients reported using a prescription drug that was association with an increase in INR test result(s). Over-the-counter (OTC) medication use topped the list of alternative medicines resulting in increased INR test results with 67% of study patients taking one or more OTC products. Bleeding was associated with concomitant medication use including traditional OTC medications and newer alternative medicines. "Eighty-seven (51%) of the 171 patients reported a bleeding event in 386 (15%) of the 2,660 survey weeks."1 Patients reported the following bleeding categories and frequencies:

  Bleeding Events Observed1

% Experienced

  Excessive bruising*




  Blood in stool


  Excessive bleeding from cut


  Excessive bleeding from tooth extraction


*beyond typical warfarin bruising

Risks of bleeding were highlighted by acetaminophen use (142 events) and elevated INR test results (130 events) in study patients. Interestingly, there seemed to be a seasonal variation of bleeding risk without explanation.

Only one patient enrolled in the study experienced a severe (major) bleeding event requiring hospitalization. The patient reported using several alternative medicines, some known to increase INR test results in patients taking warfarin (coenzyme Q10 and vitamin E 800 IU/day.

In Part 2, we highlight the specific alternative medicine's involved in elevated INRs and documented bleeding events.

  1. Shalansky S, Lynd L, Richardson K, Ingaszewski A, Kerr C. Risk of warfarin-related bleeding events and supratherapeutic international normalized ratios associated with complementary and alternative medicine: a longitudinal analysis. Pharmacotherapy. 2007 Sep;27(9):1237-47.