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BMJ. 2007 November 17; 335(7628): 1002–1003.
Published online 2007 November 8. doi:  10.1136/bmj.39371.489398.80
PMCID: PMC2078650

Improving adherence to drugs for hypertension

Knut Schroeder, general practitioner1 and Tom Fahey, professor and head of department2

General practitioners who provide effective explanations of treatment achieve better results

Effective drug treatments are available for many chronic conditions. But management of chronic diseases can be successful only if health professionals prescribe appropriately and if drugs are taken appropriately to maximise their pharmacological effects. A systematic review of interventions to improve adherence stated that, “ways to help people follow medical treatments could have far larger effects on health than any treatment itself.”1 Interventions to improve adherence in people with hypertension have targeted patients and health professionals, but studies in the past have often lacked methodological rigour.

Adherence to long term treatment for chronic illnesses in developed countries is about 50%, and rates are probably even lower in developing countries.2 In this week's BMJ, Qureshi and colleagues report the results of a cluster randomised controlled trial of a simple educational package delivered to 78 general practitioners in Karachi, Pakistan.3 The intervention consisted of a one day “intensive training session” that covered knowledge and skills needed for the management of hypertension and included “explanations of therapy and use of appropriate communication strategies.” The trial included 200 people aged 40 or over with high blood pressure who were taking antihypertensive drugs. Adherence, defined as “correct dosing” (the proportion of doses taken), was measured using electronic drug monitors, and 178 of the participants completed the six week follow-up. The study took place six months after the general practitioners' training session. Adherence was significantly higher in the intervention group. Subgroup analysis of people with good versus poor adherence showed a clinically important decline in systolic (8.3 mm Hg; P=0.04) and diastolic blood pressure (3.8 mm Hg; P=0.1). In a country with relatively low levels of blood pressure control and a high prevalence of hypertension, the results of this study are encouraging.4

The study is important because it is a randomised controlled trial that uses a pragmatic intervention. Electronic drug monitoring, one of the more reliable methods of measuring adherence, was used to measure outcomes. The study has limitations—although the intervention seemed to be effective, it tells us little about which parts of the intervention helped increase adherence. We also do not know whether the effect is likely to be sustained because the follow-up period of six weeks is short, especially as treatment for this condition is usually life long.

Randomised controlled trials of interventions to improve adherence have found that no simple interventions and only a few complex ones (interventions built up from several components, which may act independently and interdependently)5 are effective. In general, they have led to small improvements in adherence.1 6 7 In hypertension specifically, reducing the number of doses and simplifying drug regimens as well as some complex interventions seem to be effective.8 Educational interventions aimed at health professionals and patients are unlikely to result in clinically important reductions in blood pressure. An organised system of regular follow-up is probably the best way to achieve adequate blood pressure control.9

The association between adherence and control of blood pressure is far from clear. Adherence to drugs that lower blood pressure seems to be higher in randomised trials than in observational studies, perhaps because of a selection bias towards more motivated participants.10 In addition, adherence to treatment may vary between people with newly diagnosed hypertension and those with established disease.

Suboptimal adherence to prescribed drugs is a global health problem, and international and national initiatives have looked at ways to improve adherence, particularly in chronic conditions.2 11 Many studies in the past were of poor methodological quality. Any interventions that aim to increase drug adherence in primary care will probably be complex and will need to be developed rigorously.5 Funding bodies should take the need for development of interventions seriously and provide resources for conducting pilot work.

When dealing with a patient with hypertension who has not reached his or her target blood pressure, adherence to drugs is just one of several areas of management that need to be considered, including errors of measurement, white coat syndrome, antagonising drugs, and secondary hypertension.12 In this context, Qureshi and colleagues show that providing explanations and communicating with patients can enhance adherence and may also improve blood pressure control.

In addition to primary preventive measures, people with high blood pressure in both developed and developing countries need access to effective antihypertensive drugs. Particularly in settings where drug adherence is low, people will be more likely to take their drugs if health professionals have knowledge and skills in improving adherence. As Qureshi and colleagues' study shows, education of health professionals can achieve this goal.3

Notes

Competing interests: None declared.

Provenance and peer review: Commissioned; not externally peer reviewed.

References

1. Haynes RB, Yao X, Degani A, Kripalani S, Garg A, McDonald HP. Interventions for enhancing medication adherence. Cochrane Database Syst Rev 2005;(4):CD000011.
2. World Health Organization. Adherence to long term therapy: evidence for action. 2003. www.emro.who.int/ncd/Publications/adherence_report.pdf
3. Qureshi NN, Hatcher J, Chaturvedi N, Jafar TH; for the Hypertension Research Group. Effect of general practitioner education on adherence to antihypertensive drug: cluster randomised controlled trial. BMJ 2007;335:1030-3. doi: 10.1136/bmj.39360.617986.AE
4. Jafar TH, Levey AS, Jafary FH, White F, Gul A, Rahbar MH, et al. Ethnic subgroup differences in hypertension in Pakistan. J Hypertens 2003;21:905-12. [PubMed]
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8. Schroeder K, Fahey T, Ebrahim S. Interventions for improving adherence to treatment in patients with high blood pressure in ambulatory settings. Cochrane Database Syst Rev 2004;(3):CD004804.
9. Fahey T, Schroeder K, Ebrahim S. Interventions used to improve control of blood pressure in patients with hypertension. Cochrane Database Syst Rev 2006;(4):CD005182.
10. Wetzels G, Nelemans P, Shouten JS, Prins MH. Facts and fiction of poor compliance as a cause of inadequate blood pressure control: a systematic review. J Hypertens 2004;22:1849-55. [PubMed]
11. Horne R. Concordance, compliance and adherence in medicine taking—a scoping exercise. SDO/76/2004. www.sdo.lshtm.ac.uk/sdo762004.html
12. Mulrow CD, ed. Evidence-based hypertension. London: BMJ Publishing Group, 2001

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