Published: September 2012


Complementary Corner: Dangerous Liaisons

Prescriber Update 33(3): 28
September 2012

A fatal adverse reaction report involving warfarin and an unknown Chinese herbal remedy is a reminder of the importance in asking patients about the use of complementary and alternative medicines (CAMs).

The patient suffered a fall resulting in extensive bruising and was admitted to hospital two days later. On admission the patient's INR was raised (6.2); although the INR was corrected, the patient's condition deteriorated and they passed away. The patient's INR was reported to be well controlled on warfarin before beginning the herbal medicine.

The use of CAMs is extensive amongst the elderly, as high as 27.7% according to one US study1. Concomitant use of CAMs with conventional medicines, both prescription and non-prescription is also widespread in the elderly2.

Herbal products may interact with anticoagulants in a number of different ways3. For example, mistletoe may have coagulant activity, while products such as feverfew, garlic, ginger and ginkgo may have anticoagulant activity3. Meadowsweet, poplar and willow may contain salicylate components and St John's wort has been suggested to increase the metabolism and clearance of some anticoagulants1, 3.

Research has shown that over 40% of patients do not discuss the use of CAMs with their doctor4. This has also been seen in a New Zealand study, where 54% of patients had not discussed their CAM use with their oncologist5. Prescribers and pharmacists are in a key position to determine those patients who are taking both CAMs and conventional medicines concurrently. Healthcare professionals are reminded to ask patients about use of CAMs and to report any suspected adverse drug reactions to the Centre for Adverse Reactions Monitoring (CARM).

  1. Williamson E, Driver S, Baxter K. 2009. Stockley's Herbal Medicines Interactions. London: Pharmaceutical Press.
  2. Elmer GW, Lafferty WE, Tyree PT, et al. 2007. Potential interactions between complementary/alternative products and conventional medicines in a Medicare population. Annals of Pharmacotherapy 41: 1617-24.
  3. Barnes J, Anderson LA, Phillipson JD. 2007. Herbal Medicines. London: Pharmaceutical Press.
  4. Giveon SM, Liberman N, Klang S, et al. 2004. Are people who use "natural drugs" aware of their potentially harmful side effects and reporting to family physician? Patient Education and Counseling 53: 5-11.
  5. Chrystal K, Allan S, Forgeson G, et al. 2003. The use of complementary/alternative medicine by cancer patients in a New Zealand regional cancer treatment centre. New Zealand Medical Journal 116: U296.
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