Prevalence of Polypharmacy, Polyherbacy, Nutritional Supplement Use and Potential Product Interactions among Older Adults Living on the United States-Mexico Border

The use of multiple medications, herbs or nutritional supplements can lead to adverse consequences, particularly in the elderly. A significant consequence resulting from polypharmacy, polyherbacy and nutritional supplement use is the potential for interactions to occur among the various products. The primary objective of this study was to estimate the prevalence of polypharmacy, polyherbacy, nutritional supplement use and potential product interactions among older adults living on the US-Mexico border.

This was a descriptive study that involved the administration of a bilingual (English/Spanish) questionnaire to a convenience sample of adults aged ≥60 years recruited from senior centres located within the most populated US-Mexico border region from June 2005 to March 2006. Participant demographics were collected in addition to information about current use of prescription medications, over-the-counter (OTC) medications, herbal products and nutritional supplements (i.e. nutraceuticals and vitamins or minerals). The outcomes measured were the number of prescription medications, OTC medications, herbal products, vitamins/minerals and nutraceuticals per participant. Furthermore, the number of potential interactions and major interactions between drugs, herbal products and nutritional supplements were identified for each participant. Additionally, product use patterns between men and women and among locations within the border region were compared.

One-hundred-and-thirty participants (mean age 71.4 years) were recruited to complete the questionnaire. The prevalence of polypharmacy among all participants was 72.3% (n = 94), with 38.5% (n = 50) taking five or more concomitant medications (major polypharmacy). Twenty-one participants (16.2%) in the study sample reported taking two or more herbal products (polyherbacy). Thirty-four participants (26.2%) reported taking two or more vitamin/mineral supplements and nine (6.9%) reported using two or more nutraceuticals. Participants living on the US side of the border had higher rates of major polypharmacy, polyherbacy and use of nutritional supplements than those living on the Mexican side of the border. Overall, there were no significant differences in medication, herbal product and nutritional supplement use patterns between men and women. Evaluation of potential interactions revealed that 46.2% (n = 60) of participants were at risk of having at least one potential drug-drug interaction. Regarding drug and herbal product-supplement interactions, 31.5% (n = 41) of participants were at risk of having at least one possible interaction.

The prevalence of polypharmacy among older adults living on the US side of the border was similar to national trends (estimates suggest that one-quarter to one-half of US adults aged ≥65 years take five or more medications). However, polypharmacy was less common in older adults living on the Mexican side of the border. Additionally, herb use was higher in older adults living on the US-Mexico border than has been reported in national surveys of US adults, which indicate that less than one-quarter of adults have used a herbal product within the previous 12 months. Furthermore, this study demonstrated that older adults living on the US side of the border consumed more herbs and nutritional supplements than their Mexican counterparts. In addition to describing product use patterns on the border, these findings suggest that almost half of the older adult participants were at risk for a potential drug-drug interaction, with approximately one-third having a potential interaction between their medications, herbs or nutritional supplements.