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Adherence Update

Physician adherence to guidelines
Money talks
Adverse events talk too

Concordance, compliance, adherence, or persistence (readers can choose whichever most soothes their prejudices) is so important that Bandolier keeps a weather eye open for anything of interest or importance. The default condition is to find nothing either interesting or important, but just recently a few have swum into our ken that are interesting, and may be important. A quick canter through them, then.

Physician adherence to guidelines

Improving treatment for hypertension is a good thing. In Canada a hypertension education programme began in 1999, with annual updates for evidence-based hypertension management recommendations, with an extensive implementation programme to enhance guideline uptake. A new report [1] examined two databases in Ontario to see what changes the programme had made.

The first database was for all treated hypertensives in a register of cardiovascular drug dispensing between 1998 and 2003. The second was for all treated elderly hypertensives without diabetes between 1994 and 2002. Results, in terms of annualised percentage change in prescribing of all antihypertensive drugs, are shown in Figure 1. In both databases, modest changes in prescribing before the introduction of the guideline and education programme were replaced by large increases in prescribing of antihypertensive drugs. Prescribing changes by class were consistent with programme guidance.

Figure 1: Annualised percentage changes in total hypertensive medicine prescribing in two databases before and after the introduction of the Canadian guideline and education programme in 1999

A second study [2] described a randomised study of 36 physicians and nurse practitioners, where an individualised intervention with advice concerning the individual patient, together with general guidance was compared with general guidance alone. The study covered about 4,500 patients, with an average age of 65 years.

In the study there was a greater increase in the proportion of patients whose prescribing was guideline concordant with individualised advice (11%) than with general guidance alone (4%). The proportion of patients with adequate blood pressure control increased from 39% to 47% with individualised guidance, and from 43% to 45% with general guidance alone. Overall, though, blood pressure changes (a 2 to 3 mmHg fall for systolic and diastolic) were the same for each group.

Money talks

We know that patient adherence to therapy is low, and the oft-quoted figure is that half of prescribed medicines are not taken. It is not always clear the extent to which any co-payments make a difference, but a new US study [3] suggests that co-payment can be an important factor.

The study was conducted in prescription management databases in Colorado and Nevada, with about 270,000 members, for six classes of drugs (calcium channel blockers, statins, oral contraceptives, inhaled corticosteroids, angiotensin receptor blockers and ACE inhibitors). The number of prescribed days covered was calculated for each class, and switching of drugs analysed, depending on whether the drug was generic (co-payment $5-$20), preferred brand name ($15-$40), or non-preferred brand name ($30-$60). The study followed 7,500 new prescriptions over one year (90% in middle or high income homes).

Over the year in these drug classes, the proportion of days covered was 56%. Results for individual classes are in Figure 2. The proportion of days covered was greatest for generics (59%) than preferred (57%) or non-preferred (52%). There were also fewer switches for generics (14%) than for preferred (20%) and non-preferred drugs (28%).

Figure 2: Average number of days covered by prescriptions in six drug classes

Adverse events talk too

Interviewing patients who are non-adherent demonstrates that adverse events are a major concern to patients. A Dutch study [4] examined 232 chronic prescriptions for long-term medicines. Almost half (46%) were not refilled over three months, and about a quarter of these patients did not refill their prescriptions because of adverse events.

Talking to patients about adverse events can help [5], but it may well depend on how the adverse event rates are described. A randomised trial in 120 subjects given information about medicine adverse events found they were more likely to be compliant, and had less fear (Figure 3), when presented with information about adverse events in percentage terms than in words (some people may experience....). Given information in words, the overestimation of risk to themselves was almost 10-fold.

Figure 3: Influence of presentation of adverse event description on compliance intention and fear of adverse events


This is a hugely important, though complicated, area. Many different aspects combine to influence professional and patient behaviour. While there is considerable evidence about the scale of the problem, there is considerably less about how to change things for the better. Bandolier will keep looking.


  1. NR Campbell et al. The impact of the Canadian Hypertension Education Program on antihypertension prescribing trends. Hypertension 2006 47: 22-28.
  2. MK Goldstein et al. Improving adherence to guidelines for hypertension drug prescribing: cluster randomised controlled trial of general versus patient-specific recommendations. American Journal of Managed Care 2005 11: 677-685.
  3. WH Shrank et al. The implications of choice. Prescribed generic or preferred pharmaceuticals improves medication adherence for chronic conditions. Archives of Internal Medicine 2006 166: 332-337.
  4. JC Hugtenburg et al. Initial phase of chronic medication use; patients' reasons for discontinuation. British Journal of Clinical Pharmacology 2005 61: 352-354.
  5. SD Young, DM Oppenheimer. Different methods of presenting risk information and their influence on medication compliance intentions: results of three studies. Clinical Therapeutics 2006 28: 129-139.

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