Dietary Supplements and Prescription Drugs: Concomitant Use Continues to Rise
September 1, 2014
ABSTRACT & COMMENTARY
Dietary Supplements and Prescription Drugs: Concomitant Use Continues to Rise
By Howell Sasser, PhD
Associate, Performance Measurement, American College of Physicians, Philadelphia, PA
Dr. Sasser reports no financial relationships relevant to this field of study.
- Two recent reports of population surveys show rates of dietary supplement use
between 50% and 70%.
- One report shows those who have clinically confirmed medical conditions are more than twice as likely as those without such conditions to report using both prescription medications and dietary supplements.
- Women and the elderly are also more likely to combine prescribed drugs and dietary supplements.
SYNOPSIS: Two recent studies have found that concomitant use of prescription medications and dietary supplements is common. Factors associated with concomitant use include female sex and older age. These findings reinforce the need for frequent communication between physicians and their patients about the full treatment "portfolio" to avoid undesirable interactions.
SOURCES: Farina EK, et al. Concomitant dietary supplement and prescription medication use is prevalent among U.S. adults with doctor-informed medical conditions. J Acad Nutr Diet 2014 Apr 4; pii: S2212-2672(14)00106-3. doi: 10.1016/j.jand.2014.01.016. [Epub ahead of print].
Kiefer DS, et al. The overlap of dietary supplement and pharmaceutical use in the MIDUS national study. Evid Based Complement Alt Med 2014;2014:823853. doi: 10.1155/2014/823853. Epub 2014 Apr 16.
The use of prescription medications (PM) is ubiquitous among Americans. A 2013 study found that 68% of those surveyed took at least one PM regularly and slightly more than half took two or more.1 Other studies have found that as many as 50% of Americans use one or more dietary supplements (DS) regularly.2 The potential for PM-DS interactions (as well as PM-PM and DS-DS effects) is a pressing medical concern and the subject of continuing population research. In the first half of 2014, two groups published findings on the frequency and characteristics of concomitant PM and DS use. This article summarizes both papers and considers the impact of their findings.
Farina and colleagues extracted PM and DS data from the 2005-2008 cycle of the National Health and Nutrition Examination Survey (NHANES). The NHANES subset used for study (n = 9950) was weighted to represent the U.S. population > 20 years of age. Aside from those with missing data, the only significant exclusion was pregnancy. Use of PM and DS (both in the past 30 days) was recorded through participant interviews with computer-based aids to guide accurate, standardized classification. Participants also reported on a number of "doctor-informed medical conditions" (DIMC) (i.e., "Has a doctor ever told you that you have"), grouped in broad categories such as cancer, heart/vascular, and respiratory.
Of the NHANES sample, 57.1% of respondents reported using at least one PM, 51.3% reported using at least one DS, and 34.3% reported using both. Those with any DIMC were more than twice as likely to report concomitant PM and DS use than those with none (odds ratio [OR], 2.62; 95% confidence interval [CI], 2.13-3.21). Others more likely to report concomitant use were women, those with more education (a gradient from less than high school to college graduate), and older people (60 years or older, as compared with those age 20-39 and age 40-59). Study respondents using more than one PM or DS were also significantly more likely to report use in both categories (OR, 1.41; 95% CI, 1.20-1.66; and OR, 1.57; 95% CI, 1.26-1.97, respectively).
Kiefer and colleagues analyzed data from Phase 2 of the Midlife in the United States (MIDUS 2) study. MIDUS was a national survey conducted using random-digit dialing and other techniques. Participants were residents of the continental United States between the ages of 25 and 74 years. Those completing a telephone survey and a self-report questionnaire (n = 3876) were included in the present analysis. The questionnaire included items in which respondents identified medical conditions for which they had taken PM, and identified DS they used, in both cases from choices on a list and in the past 30 days.
Of the MIDUS population, 67.6% reported using at least one PM, 69.7% reported using at least one DS, and 49.6% reported using both. Those reporting use of both PM and DS were more likely to be female, were older on average, less affluent (based on median income), and somewhat less well educated as compared with those reporting no use in either category. Those reporting PM and DS use were also more likely to be female and older, as compared with those reporting PM use only.
These reports are a striking indication of the extent to which a variety of substances have become a routine part of many Americans’ health care practices. It would appear that DS are part of both the preventive care routine and the response to disease, although it is not possible to tell from these data whether either kind of use originates in patient desires, practitioner recommendations, or a combination of both. Also striking are the indications that concomitant use cuts across some demographic categories. Although it is clear that PM+DS users are more likely to be female, the NHANES population showed greater use among those with more education, while the MIDUS population showed higher use among those with less education. Similarly, MIDUS concomitant users were more likely to be less affluent, while the NHANES study showed a more even distribution across levels of income. In this context, it is worth repeating that both studies included nationwide (in the case of MIDUS continental United States) samples. These results go beyond the usual hotbeds of complementary and alternative medicine use.
Even as use of DS appears to be spreading, it is important to be clear about what exactly counts as DS. The NHANES study used 18 categories that included, among other things, multivitamins, multiminerals, amino acids, botanicals, calcium, probiotics, and antacids in over-the-counter (OTC) formulations. It also was careful to note when PM were formulated to include ingredients that would otherwise be considered DS (for instance, a statin with niacin), and when substances could be either OTC or by prescription, depending on dose. The MIDUS study asked about vitamin, mineral, or herbal supplements. The breadth of what might count as DS use, and the possibility of "double-dipping" — the same agent being taken in OTC and prescription forms — complicates the clinician’s task in sorting out with the patient what he or she is taking and with what therapeutic goal.
And yet, the message clearly is that this kind of inventory is more and more urgent. Stories of elderly patients coming to doctors’ visits with shopping bags of prescription medications might pale in comparison with stories of such patients coming in with both their prescription medications and their supplements. The lists may be long, but the need is great. Several popular DS are known to have significant interactions with PM. St. John’s wort, ginseng, and gingko are among the DS best studied in this respect, but others likely have the potential to alter, up- or down-regulate the effects of various PM.3 This, of course, is in addition to the many known and suspected interactions among PM, and between PM and foods not generally thought of as DS (for instance, grapefruit and its effect on the cytochrome P450 drug metabolism pathway).4
With these considerations in mind, it is possible to make a few recommendations for clinicians who need to review the totality of PM and DS use with their patients:
1. Don’t wait to be asked. The data make clear that more people than not are using DS — defined broadly — at least some of the time. Asking a patient about his/her DS use opens the door to conversation and may ease any concerns patients may have about admitting to using "unofficial" remedies.
2. Be systematic. The Farina article includes an appendix listing the 18 categories of DS included in the NHANES survey. A paper or electronic version of such a list could be a good tool to use during a clinical interview.
3. Ask clarifying questions. If a patient says that s/he uses some substance, appropriate questions about dose, delivery form/format, frequency, and therapeutic purpose(s) should follow. Bear in mind that some DS have multiple uses (for example, antacids used for their labeled indication and/or as sources of calcium or other minerals). Note also that some supplements contain multiple agents.
4. Ask often. Patients’ DS portfolios can be expected to change and will need periodic updating. DS use is pragmatic and driven by many factors including cost, availability, assessment of effects, and even seasonal variation (for example, Vitamin D supplementation in northern latitudes in the winter months). Here again, asking about therapeutic goals may help to guide a discussion of various brands and formulations and reveal important details about patterns of DS use.
5. Be respectful. Patients can recognize when a clinician is skeptical or dismissive. This may inhibit current and future discussions. It is never wrong to point out potentially problematic side effects or interactions, but doing so in a way that shows respect for the patient’s autonomy and capacity to make informed choices increases the chance that such messages will be given due consideration.
- Zhong W, et al. Age and sex patterns of drug prescribing in a defined American population. Mayo Clinic Proc 2013;88:697-707.
- Gahche J, et al. Dietary supplement use among U.S. adults has increased since NHANES III (19881994). NCHS Data Brief No 61. Hyattsville, MD: National Center for Health Statistics; 2011.
- Gardiner P, et al. Herbal and dietary supplementdrug interactions in patients with chronic illnesses. Am Fam Physician 2008;77:73-78.
- Bailey DG, et al. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? CMAJ 2013;185:309-316.
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