A new study in The Annals of Pharmacotherapy sought to determine the prevalence of complementary and alternative medicine (CAM) product use concurrent with conventional medications, prescription and nonprescription in a Medicare population and assess the risk for adverse interactions. Despite the high prevalence of CAM product use among the elderly, little is known about the extent of concurrent CAM-conventional medicine use and the potential for adverse reactions.

Researchers performed retrospective analysis on Cardiovascular Health Study interview data from 1994, 1995, 1997 and 1999. The prevalence of concurrent combinations of CAM products and conventional drugs was tabulated. The adverse interaction risks were categorized as unknown, theoretical and significant. The data consisted of 5,052 participants with a median age of 75.

According to the study, the percent of participants using CAM products during the 4 time periods was 6.3%, 6.7%, 12.8% and 15.1%. The percent using both CAM products and conventional drugs was 6.0%, 6.2%, 11.7% and 14.4%. Of these, 294 (5.8%) individuals took combinations considered to have a significant risk for an adverse interaction. Combinations with risk were observed on 393 separate interviews. Most (379) involved a risk of bleeding due to use of ginkgo, garlic, or ginseng together with aspirin, warfarin, ticlopidine or pentoxifylline. An additional 786 observations of combinations were considered to have some, albeit theoretical or uncertain, risk for an adverse interaction.

Researchers concluded that concurrent use of CAM products and conventional medicines in a Medicare population was common. It was also strongly suggested that further research is needed to define the risks of combining ginkgo and garlic supplements with aspirin.