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Keywords:

  • adherence;
  • therapeutic intensity;
  • multiple medication

ABSTRACT

Purpose

To estimate non-adherence in relation to the therapeutic intensity (TI) and the number of dispensed drugs per individual and study whether the TI can be used as an estimator of non-adherence with an increasing number of drugs.

Methods

The study comprised an individual-based register of all dispensed outpatient prescriptions in Sweden in 2006, including 6.2 million individuals. The applied definition of drug was the chemical entity or substance comprising the fifth level in the World Health Organisation's Anatomic, Therapeutic, Chemical classification. The defined daily dosage per individual during 12 months was applied as an indicator of the TI.

Results

We found a positive linear relation between the TI and the increasing number of dispensed drugs per individual, both for men and women. We found a slightly diminishing TI with an increasing number of drugs only for the age groups above 70 years, at a level above 13 drugs per individual.

Conclusions

The linear relationship between the TI and the increasing number of dispensed drugs per individual provides poor support for using decreasing TI as an estimator of non-adherence. The low rate of cost-related non-adherence in Sweden might contribute to explaining the linear relationship. Copyright © 2011 John Wiley & Sons, Ltd.