The co-use of conventional drugs and herbs among patients in Norwegian general practice: a cross-sectional study

Djuv et al. BMC Complementary and Alternative Medicine 2013, 13:295 http://www.biomedcentral.com/1472-6882/13/295 RESEARCH ARTICLE Open Access The co-use of conventional drugs and herbs among patients in Norwegian general practice: a cross-sectional study Ane Djuv1,2*, Odd Georg Nilsen1,2 and Aslak Steinsbekk3 Abstract Background: Different patient groups are known to use herbal remedies and conventional drugs concomitantly (co-use). This poses a potential risk of herb-drug interaction through altering the drug’s pharmacokinetics or pharmacodynamics. Little is known about co-use among patients in general practice. The primary aim of this study was to compare patients in general practice that co-use herbal remedies and conventional drugs with those who do not. The secondary aim was to register the herb-drug combinations with potential clinical relevant interactions among the co-users. Method: A questionnaire based cross-sectional study conducted in the autumn 2011 in a general practice office with four general practitioners (GPs) and one intern in Western Norway. Adults >18 years who came for an office visit were invited. The questionnaire asked about demographics, herbal use, conventional drug use and communication about herbal use. Multivariable logistic regression was used to compare co-users to the other patients. Results: Of the 381 patients who completed the questionnaire, the prevalence of herbal use was 44%, with bilberry (41%), green tea (31%), garlic (27%), Aloe vera (26%) and echinacea (18%) as the most frequently used. Among those using conventional drugs regularly, 108 (45%) co-used herbs. Close to 40% of patients on anticoagulants co-used herbs, with garlic and bilberry as the most frequent herbs. Compared to all other patients, co-users had significantly (p < 0.05) increased odds to be female (adjOR 2.0), age above 70 years (adjOR 3.3), use herbs to treat an illness (adjOR 4.2), use two or more herbs (polyherbacy, adjOR 12.1) and having experienced adverse effects of herbal use (adjOR 37.5). Co-use was also associated with use of analgesics or dermatological drugs (adjOR 5.1 and 7.9 respectively). Three out of four patients did not discuss herbal use with any health care professional. Conclusion: A sizable proportion of the GP patients co-used herbs with conventional drugs, also combinations with reported interaction potential or additive effects like anticoagulants and garlic. The low disclosure of herbal use to their GP, polyherbacy and the risk of interactions in vulnerable groups like elderly and chronically ill patients, warrant increased awareness among GPs. Keywords: Herb-drug interaction, General practice, Safety, herbal use, Disclosure, Complementary therapy, Elderly, Polyherbacy, Polypharmacy * Correspondence: 1 Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway 2 St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway Full list of author information is available at the end of the article © 2013 Djuv et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Djuv et al. BMC Complementary and Alternative Medicine 2013, 13:295 http://www.biomedcentral.com/1472-6882/13/295 Page 2 of 11 Background In the last two decades there has been a considerable increase in the herbal remedy market [1,2]. Interactions between herbal remedies and drugs have been put on the agenda and received increased attention [3,4]. Both serious and less serious adverse interactions have been reported e.g. between the drug cyclosporine and St. Johns wort (Hypericum perforatum), and between drugs like warfarin or aspirin which are reported to interact with a range of herbs like garlic (Allium sativum), cranberry (Vaccinium oxycoccos), Ginkgo Biloba, ginger (Zingiber officinale) and grape fruit (Citrus paradisi) [5-9]. Co-use of herbs and drugs might alter the drug’s pharmacokinetics and/or pharmacodynamics, hence causing unexpected adverse effects of the drug [10-13]. Studies have reported extensive use (40-56%) of herbs in the general population [14-16]. The 2007 National Health Interview Survey, USA, reported that nearly 20% of the general population were using herbs [17]. The typical herb user was female, aged 30 to 69 years, with higher education or hospitalized in the last year [17]. Forty-one per cent of USA adults reported the use of herbal remedies to self-treat before seeking medical care from a physician [14]. Only 50% of herb users inform their physician about it [14]. In addition, the health care professionals rarely ask the patients about the use of herbs or other types of complementary and alternative medicine [18]. ”The doctor did not ask” is the common phrase explaining the lack of communication [19]. The general practitioners (GPs) also tend to underestimate the use [18]. It is therefore important to have knowledge about the characteristics of herb users in general and co-users in particular to make health professionals more aware. It is reported that up to 40% in various patient groups co-administrate herbal remedies and drugs [20-22]. One study found that 40% of pregnant women used herbal remedies and about 85% of these co-used conventional drugs [21]. The use of herbal remedies among adults with cancer is reported to be between 30-55% [15,23] and one study found that almost 40% co-use herbal remedies and chemotherapy [24]. Elderly patients have more poly-pharmacy problems and are more vulnerable to interactions because of altered pharmacokinetics and decreased health in general [25]. Considering that 13-47% of elderly patients report to consume herbs [26,27] and 31- 75% of these co-use herbs and prescribed conventional drugs [28,29], the risk of adverse interactions might be high. About 50% of the general population have one or more chronic conditions and as the elderly, they have a high care rate and polypharmacy (50%) [30]. They also tend to use more herbal remedies, which increase the possibility of herb-drug interactions [31]. Despite the large reported use of herbs and co-use of herbs and conventional drugs in the general population and in various patient groups, few studies have been performed among patients in primary care and general practice in particular. About 40% of the patients in primary care clinics in USA believed that taking prescription medications and herbal remedies together was more effective than taking either alone and nearly 50% of the herb users co-used drugs [32]. An Israeli study on co-use among patients in general practitioner’s offices, reported 36% of herbal use and approximately 30% were co-users [33]. GPs are the first medical contact within the health care system, (...truncated)