Abstract
BackgroundMany consumers use natural health products (NHPs) concurrently with prescription medications. As NHP-related harms are under-reported through passive surveillance, the safety of concurrent NHP-drug use remains unknown. To conduct active surveillance in participating community pharmacies to identify adverse events related to concurrent NHP-prescription drug use.Methodology/Principal FindingsParticipating pharmacists asked individuals collecting prescription medications about (i) concurrent NHP/drug use in the previous three months and (ii) experiences of adverse events. If an adverse event was identified and if the patient provided written consent, a research pharmacist conducted a guided telephone interview to gather additional information after obtaining additional verbal consent and documenting so within the interview form. Over a total of 112 pharmacy weeks, 2615 patients were screened, of which 1037 (39.7%; 95% CI: 37.8% to 41.5%) reported concurrent NHP and prescription medication use. A total of 77 patients reported a possible AE (2.94%; 95% CI: 2.4% to 3.7%), which represents 7.4% of those using NHPs and prescription medications concurrently (95%CI: 6.0% to 9.2%). Of 15 patients available for an interview, 4 (26.7%: 95% CI: 4.3% to 49.0%) reported an AE that was determined to be “probably” due to NHP use.Conclusions/SignificanceActive surveillance markedly improves identification and reporting of adverse events associated with concurrent NHP-drug use. Although not without challenges, active surveillance is feasible and can generate adverse event data of sufficient quality to allow for meaningful adjudication to assess potential harms.
Highlights
[1] Of note, natural health products (NHPs) are frequently used by patients with chronic or recurrent conditions; these patients are the most likely to be prescribed conventional medications. [12,13,14] Since the likelihood of an adverse event (AE), including drug interactions, increases with the number of medicinal products used, it is hypothesized that patients who concurrently use prescription medications and NHPs are at greater risk for an AE than if they were using either product alone and represent a population of particular interest with respect to exploring the safety of NHPs. [10]
Among those using NHPs and prescription medicines concurrently, 77 patients reported experiencing AEs. (Tables 3 and 4) Approximately one-third (36%; n = 27) of patients who reported an AE originally agreed to be contacted for the follow-up telephone interview
Not without its challenges, active surveillance in pharmacies is feasible, and markedly increases both the number and quality of AE reports in comparison to passive surveillance. [53,54,55,56] When comparing our results to data derived from passive surveillance, we found that the Health Canada AE database (Canada Vigilance) has a total of 1544 AE reports associated with NHP use over a five year period from passive surveillance of over 30 million Canadians, which results in a median incidence rate of approximately 0.0008%
Summary
Recent national surveys in North America, Australia and Europe suggest that more than half of the population uses dietary supplements, known as natural health products (NHPs) or complementary medicines, including herbs, vitamins, minerals and other supplements. [1,2,3,4,5,6] In developing countries, use is even higher; in Africa for example, 80% of the population uses African Traditional Medicine, 90% of which is plant-based. [5].NHPs are generally considered to be safe by the public, despite the growing evidence that this is not always the case. [1,7,8,9,10,11]Particular caution is warranted when NHPs are used in combination with prescription medications due to the potential for interactions. [1] Of note, NHPs are frequently used by patients with chronic or recurrent conditions; these patients are the most likely to be prescribed conventional medications. [12,13,14] Since the likelihood of an adverse event (AE), including drug interactions, increases with the number of medicinal products used, it is hypothesized that patients who concurrently use prescription medications and NHPs are at greater risk for an AE than if they were using either product alone and represent a population of particular interest with respect to exploring the safety of NHPs. [10].In most countries, the primary system of identifying postmarketing AE related to therapeutic products is passive surveillance (i.e., voluntary spontaneous reporting). [15] Increasingly, these passive surveillance systems are used for collecting information about NHP-related AEs, as is the case in the United States, Canada, the United Kingdom, Australia, and Germany. [15,16,17,18] A strength of passive surveillance is its potential to identify AEs from large populations that are using products under real world circumstances, which should theoretically allow for the identification of new and/or rare adverse events. [16,17].Passive surveillance depends on voluntary reporting of adverse events by health care practitioners (and, in some cases, patients) and is known to be limited by substantial under-reporting with estimates suggesting that perhaps less than 1% of AEs are ever reported. [16,17,18,19,20] Patients may be even less likely to report AEs associated with NHPs as compared to those associated with conventional over-the-counter medications (OTC); some may not associate NHPs with causing harms or may not consider NHPassociated AEs important enough to report. [21,22] Among health care providers, pharmacists have higher reporting rates, but like other health professionals, they too under-report suspected NHP AEs in comparison to those for conventional pharmaceuticals. [19,23] This may be due to lack of awareness of their patients NHP use: studies in the UK and Australia have found that a majority of pharmacists does not ask customers about NHP use, including when receiving reports of suspected AEs associated with prescription medicines. [24,25] physicians are poor at reporting drug-related harms, and they do not routinely inquire about their patients’ NHP use. [19,23,26] Combined, these patient and health care provider factors suggest that passive surveillance has important limitations with respect to identifying NHP-related harms.Another approach to investigating drug safety is active surveillance which ‘‘seeks to ascertain completely the number of adverse events via a continuous pre-organized process’’. [27] Active surveillance methods are well-established for the collection of adverse event data following prescription medicine use, [28,29] but its application to pharmacovigilance of NHPs is limited to date. [12,13,14] Since the likelihood of an adverse event (AE), including drug interactions, increases with the number of medicinal products used, it is hypothesized that patients who concurrently use prescription medications and NHPs are at greater risk for an AE than if they were using either product alone and represent a population of particular interest with respect to exploring the safety of NHPs. [19,23,26] Combined, these patient and health care provider factors suggest that passive surveillance has important limitations with respect to identifying NHP-related harms. Another approach to investigating drug safety is active surveillance which ‘‘seeks to ascertain completely the number of adverse events via a continuous pre-organized process’’. To conduct active surveillance in participating community pharmacies to identify adverse events related to concurrent NHPprescription drug use
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
