Background

Patients' non-adherence to prescribed medicines continues to be a significant issue¹. This is particularly important for coronary heart disease (CHD) because the disease is highly prevalent and treatments are clearly beneficial. The aim of this study was to test the efficacy of implementation intentions² to promote adherence to medicines prescribed for CHD. Implementation intentions specify exactly when and where a behaviour will be performed (e.g. I will take my tablet before I brush my teeth, in the bathroom, before bed). The results of this pilot study are explored in the context of methodological problems associated with research in the area of adherence with medicines in CHD.

Method

Patients attending a secondary prevention CHD clinic in three Leeds practices were recruited to this randomised control trial. In the pilot study 41 patients were recruited and telephoned at 7, 28 and 90 days post-recruitment. Theory of Planned Behaviour (TPB)³ variables were measured at recruitment and at 90 days follow-up. Self-reported adherence with medicines was measured at recruitment and at each of the follow-up time points. At first, we used the MARS-5 tool to measure adherence⁴. As consistently high adherence was reported, the measure was replaced with open-ended questions (e.g. How many times have you taken this medication at a different time in the last month? What was the reason for this?).

Results

Mean scores at recruitment on the TPB variables indicated that participants had high intentions to adhere to the medicines (Mean = 6.89, SD = 0.39; maximum possible score = 7). Self-reported adherence at recruitment was close to 100% with all participants indicating 'rarely' or 'never' on four of the five MARS-5 items. The open-ended approach to exploring adherence prompted 75% of participants to admit to sometimes missing a dose or taking medicines at a different time. However, further probing revealed the frequency of this non-adherence to be low. This pattern of results was consistent across the three follow-up time points.

Discussion

Contrary to previous research⁵, adherence to medicines was reported as high in this sample. This was consistent across both measures used. It was not possible to test the proposed intervention. These unexpected findings may be due to social desirability factors. However, it seems more likely that the recruited CHD clinic patients were generally 'compliant' and take the life-threatening nature of CHD more seriously than non-attenders. The high prevalence of once-a-day dosing in treatments for secondary prevention of CHD may also be a factor in these high adherence rates.

References

1 RPSGB (1997). From compliance to concordance. Achieving shared goals in medicine taking. London: Royal Pharmaceutical Society and Merck Sharpe and Dohme.

2 Gollwitzer PM (1993). The role of intentions. In European Review of Social Psychology. (Edited by W. Stroebe, and M. Hewstone), pp.141-185. Chichester, U.K: U.K.

3 Ajzen I (1985). From intentions to actions: A Theory of Planned Behavior. In Action Control: From Cognitions to Behaviour (Edited by J. Kuhl and J. Beckmann), pp. 11-39. Germany: Springer-Verlag.

4 Horne, R. & Hankins, M. (in preparation). The medication adherence report scale (MARS).

5 Haynes RB, McKibbon KA, Kanani R (1996). Systematic review of randomized trials of interventions to assist patients to follow prescriptions for medications. Lancet, 383-386.