Impact of Dosage Frequency on Patient Compliance

  1. Carmen J Soe-Agnie, PHARMD
  1. Department of Pharmacoepidemiology and Pharmacotherapy, Universiteit Utrecht The Netherlands
  1. Address correspondence and reprint request to A.H.P Paes, Department of Pharmacoepidemiology and Pharmacotherapy, Universiteit Utrecht, PO. Box 80082, 3508 TB Utrecht, The Netherlands.


OBJECTIVE To evaluate the impact of dosage frequency on the compliance of patients who receive their medicines from community pharmacies.

RESEARCH DESIGN AND METHODS Each month, patients received a supply of their medication in a Medication Event Monitoring Systems container, which registered each opening of the package. At the end of the study, the patients received a short questionnaire. The subjects were 91 diabetic patients using oral antidiabetic agents. Patients taking insulin and those who were unable to collect their medicines from the pharmacy were excluded from the study. Compliance was defined as the percentage of doses taken during the observation period. Another parameter used was compliance with the prescribed regimen, defined as the percentage of days in which the number of tablets were taken as prescribed. As a last parameter, compliance with the prescribed dose intervals was used.

RESULTS Compliance is influenced by the frequency of doses. The compliance for this group of patients is 74.8%, with an average of 79% in the case of a dose once daily and 38% in the case of a dose three times daily. The predominant type of noncompliance in all groups was dose omissions. However, more than one-third of the patients used more doses than prescribed. Overconsumption is a frequently made mistake by patients on a one-dose daily schedule.

CONCLUSIONS The reduction of dose frequency may decrease total noncompliance, but at the same time, it increases the risk of overconsumption. Reducing the frequency does not automatically result in a better therapeutic schedule. The choice of once or twice daily should depend on the therapeutic range of the drug.

  • Received December 5, 1996.
  • Accepted April 30, 1997.
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