Volume 195 - Issue 11
Complementary medicine use in cardiovascular disease: a clinician’s viewpoint
Authors: Hosen Kiat, Yu Sun Bin, Suzanne Grant and Dennis Hsu-Tung Chang
Med J Aust 2011; 195 (11): 654-656. || doi: 10.5694/mja10.10976
Published online: 12 December 2011
Published online: 12 December 2011
Patients with cardiovascular disease may be especially prone to the adverse effects of complementary medicines
Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in Australia.1 Given the chronic nature of CVD, medical management is the most common mode of care, and medications are prescribed to most patients with CVD.2 In general practice, treatment of CVD accounts for almost one in five encounters, with hypertension the most commonly treated risk factor, followed by lipid disorders.2
Although effective management of CVD depends on a range of factors, one that is often neglected is the use of complementary medicine (CM). While CM can potentially benefit patients with CVD, it can have an adverse impact on the effectiveness of conventional CVD therapies in two main ways: through drug interaction or through reduced adherence to conventional therapies.
In Australia, CM is defined as the use of medicines containing herbs, vitamins, minerals, nutritional supplements and homoeopathic medicines.3 The popularity of CM has increased in recent years,4 and in people with CVD, rates of use have been estimated at up to 42%, with up to 21% of these patients taking herbal supplements.5
The most common types of CM taken by people with CVD are multivitamins and minerals (34% of surveyed cardiac patients), calcium (22%), vitamin E (20%) and vitamin C (14%). The most common herbal agents used are mint or lemon balm (11%), nettle (8%), green tea (7%), echinacea (6%) and garlic (6%). The use of coenzyme Q10 (3%), fish oil or omega-3 fatty acids (2%) and hawthorn (1%) are surprisingly low.5
Although CM is often considered safe by patients, harmful effects associated with its use do exist. The use of CM alongside prescription medications has the potential of reducing the effectiveness or increasing the potency of therapy. These effects may be compounded in people with CVD for several reasons. First, CM users tend to consume more than one CM product concurrently over periods of months to years.5 Second, the likelihood of interference with prescribed therapy is increased since certain medications, such as digoxin and warfarin, have a narrow therapeutic window.
Patients with CVD also tend to be elderly, are likely to suffer from multiple comorbidities and therefore are likely to be using multiple long-term medications.5 Several studies in people with CVD indicate that not only do a significant proportion use CM concurrently with prescribed therapy, but about half do not inform treating doctors about their use.5
The relatively widespread use of CM in people with CVD means it is vital that doctors are aware of CM use. Some commonly observed interactions between CM and conventional CVD medications and possible mechanisms are summarised in the Box.
Apart from the possibility of drug interactions, the bioactive components of CM products can also directly cause adverse effects. Some examples of CM that are used in the treatment of CVD (and their adverse effects) include Aloe vera (diarrhoea and potassium depletion), fenugreek (diarrhoea and hypoglycaemia), garlic (inhibition of platelet function), ginseng (insomnia), ephedra (stroke and myocardial infarction), Ginkgo biloba (bleeding) and red yeast rice (myopathy and rhabdomyolysis).7
More generally, there are safety issues associated with the quality of CMs. These relate to the lack of standard dosing, which in part is due to variations in potency, depending on where plants are grown; the possibility of contamination by pesticides and heavy metals during cultivation; and the possibility of contamination by bacteria in the storage, transport or manufacturing processes.7
The second main mechanism in which CM use may impact on effective management of CVD is through reduced adherence to prescription medications. However, a limited number of studies investigating the impact of CM on cardiovascular medication adherence show inconsistent results. Some studies report a lower adherence to prescription medications among cardiovascular patients taking CM, while others found the opposite.5
Importantly, we found in our review that CM use was not disclosed by cardiac patients up to 65% of the time. The main reasons were fear of clinician disapproval and because clinicians had not asked about CM use.5,9 This strongly suggests that clinicians need to take a less judgemental and more proactive approach to encourage patient discussion of CM use, regardless of adherence to conventional treatment.
What, then, are the identifying characteristics of a CM user? In the general population, use of CM is associated with higher levels of education and income10 but poorer self-reported health status. Although few differences have been found between cardiac patients who are CM users compared with non-users,5 it appears that people with chronic disease are more likely to use CM, especially if they have multiple comorbidities.10
As well as being aware of the potential impact of CM on prescribed therapy, clinicians should also be aware of the reasons patients use CM. About half of CM users with CVD believe that CM is of greater benefit than conventional treatment, or perceive that the CM used has proven benefits for their condition.5 Many CM users also believe that there are fewer side effects associated with “natural” therapies.5 CM therefore meets a real or perceived need for health care, and serves an important psychological function in enabling patients to manage their own health.11
Given the increasing prevalence of both CM use and CVD, it is likely that clinicians will see more cases of patients who are using CM either specifically for their cardiovascular condition or towards improving general health. Regardless of personal viewpoint, CM is now an integral part of the therapeutic armamentarium used by the Australian population. Thus, there is a need to better inform doctors about CM use and the associated potential for adverse reactions and herb–drug interactions. There are significant gaps in clinician knowledge of the risks and benefits associated with CM use, and clinicians report feeling ill-equipped to respond to patient enquiries about CM.12
Medical schools overseas, such as those in Asia, France, Germany, Switzerland and some in the United States, have incorporated CM into their medical curricula. Awareness of CM needs to be integrated into routine medical practice, such as by asking patients about CM as part of a medication review. CM modules should be included in continuing professional education programs for general practitioners and specialists alike.
The key issues and complexities of CM that should be understood include the differing definitions of CM in different countries, such as the American and Australian classifications, and the processes underlying its regulation. In Australia, for example, the Therapeutic Goods Administration regulates CM products, and the difference between “listed” medicines (which are not evaluated for efficacy) versus “registered” medicines is important.3
There is growing research on the efficacy of select CMs for various conditions. Results from robust studies show that omega-3 fatty acids may assist in the treatment of hypertriglyceridaemia,13 reduce the incidence of thrombotic stroke14and coronary heart disease,15 and may prevent sudden cardiac death in patients with prior myocardial infarction.16 Coenzyme Q10 supplements appear to reduce the symptom of statin-induced myalgia17 and may have favourable effects in those with heart failure.18 Physical therapies such as qi gong also appear helpful for hypertension19 and are likely to be beneficial in some patient groups as alternatives to higher intensity physical activity.
Furthermore, considerable efforts are being made to investigate the efficacy of CM in CVD prevention and risk factor reduction. Research bodies such as the National Institutes of Health in the US and the National Institute of Complementary Medicine in Australia are supporting studies investigating the effects of hawthorn leaf in milder forms of heart failure, the use of disodium edetate (EDTA) chelation therapy to treat coronary artery disease, vitamin D3 for prevention of CVD and melatonin for lowering hypertension. Further research is required to strengthen the evidence base for these and other CM therapies; however, certain CMs may prove to be efficacious for people with CVD, and critical awareness of this work is necessary for effective clinical practice.
The use of CM is common among patients with cardiovascular conditions and a high proportion of patients using CM believe they have remedial benefits. Many CM users also believe that CM is as safe as or safer than their prescribed treatments, and are often unwilling to inform their doctors of their use of CM products. Commonly used CM products have the potential to interfere with the intended action of prescription medications although clinician knowledge of these interactions may be limited.
We have restricted our discussion to patients with CVD, although the importance of considering CM in medical management applies equally to other patient groups, especially those with chronic disease. We emphasise the need for education about CM, so clinicians become more aware of patients’ CM use, become more knowledgeable about CM, and more capable of advising their patients about this issue.
Potential interactions of commonly used CM with cardiovascular medications6-8
Competing interests
No relevant disclosures.
Acknowledgements
We thank Lisa Wallis for assistance in manuscript preparation.
References
- Australian Institute of Health and Welfare. Australia’s Health 2008. Canberra: AIHW, 2008. (AIHW Cat. No. AUS 99.) http://www.aihw.gov.au/publication-detail/?id=6442468102 (accessed Oct 2011).
- Australian Institute of Health and Welfare. General practice activity in Australia 2005–06. Canberra: AIHW, 2007. (AIHW Cat. No. GEP 19.) http://www.aihw.gov.au/publication-detail/?id=6442467936 (accessed Oct 2011).
- Therapeutic Drugs Administration. The regulation of complementary medicines in Australia — an overview. Canberra: TGA, 2007. http://www.tga. gov.au/industry/cm-basics-regulation-overview.htm (accessed Oct 2011).
- Ernst E. Prevalence of use of complementary/alternative medicine: a systematic review. Bull World Health Organ 2000; 78: 252-257. 0_i1115443
- Bin YS, Kiat H. Prevalence of dietary supplement use in patients with proven or suspected cardiovascular disease. Evid Based Complement Alternat Med 2011; article ID: 632829. doi: 10.1155/2011/632829. 0_i1115445
- Tachjian A, Maria V, Jahangir A. Use of herbal products and potential interactions in patients with cardiovascular diseases. J Am Coll Cardiol 2010; 55: 515-525. 0_i1115447
- Cohen PA, Ernst E. Safety of herbal supplements: a guide for cardiologists. Cardiovasc Ther 2010; 28: 246-253. 0_i1115449
- Izzo AA, Di Carlo G, Borrelli F, Ernst E. Cardiovascular pharmacotherapy and herbal medicines: the risk of drug interaction. Int J Cardiol 2005; 98: 1-14. 0_i1115451
- Robinson A, McGrail MR. Disclosure of CAM use to medical practitioners: a review of qualitative and quantitative studies. Complement Ther Med 2004; 12: 90-98. 0_i1115453
- Bishop FL, Lewith GT. Who uses CAM? A narrative review of demographic characteristics and health factors associated with CAM use. Evid Based Complement Alternat Med 2010; 7: 11-28. 0_i1115455
- Bishop FL, Yardley L, Lewith GT. A systematic review of beliefs involved in the use of complementary and alternative medicine. J Health Psychol 2007; 12: 851-867. 0_i1115457
- Pirotta M, Kotsirilos V, Brown J, et al. Complementary medicine in general practice — a national survey of GP attitudes and knowledge. Aust Fam Physician 2010; 39: 946-950. 0_i1115459
- Balk EM, Lichtenstein AH, Chung M, et al. Effects of omega-3 fatty acids on serum markers of cardiovascular disease risk: a systematic review. Atherosclerosis 2006; 189: 19-30. 0_i1115461
- Iso H, Rexrode KM, Stampfer MJ, et al. Intake of fish and omega-3 fatty acids and risk of stroke in women. JAMA 2001; 285: 304-312. 0_i1115463
- Hu FB, Bronner L, Willett WC, et al. Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA 2002; 287: 1815-1821. 0_i1115465
- Zhao YT, Chen Q, Sun YX, et al. Prevention of sudden cardiac death with omega-3 fatty acids in patients with coronary heart disease: a meta-analysis of randomized controlled trials. Ann Med 2009; 41: 301-310. 0_i1115467
- Marcoff L, Thompson PD. The role of coenzyme Q10 in statin-associated myopathy: a systematic review. J Am Coll Cardiol 2007; 49: 2231-2237. 0_i1115469
- Rosenfeldt F, Hilton D, Pepe S, Krum H. Systematic review of effect of coenzyme Q10 in physical exercise, hypertension and heart failure. Biofactors 2003; 18: 91-100. 0_i1115471
- Lee MS, Pittler MH, Guo R, Ernst E. Qigong for hypertension: a systematic review of randomized clinical trials. J Hypertens 2007; 25: 1525-1532. 0_i1115474
Provenance: Not commissioned; externally peer reviewed.