Dosage frequency and drug-compliance behaviour — a comparative study on compliance with a medication to be taken twice or four times daily

Summary

The objective of the study was to investigate patient compliance with two different dosage regimens. Ethinyloestradiol 80 μg daily was prescribed to 35 female outpatients to be taken as 20 μg four times daily or 40 μg twice daily for 7 days. It was given to standardise cervical mucus before a sperm cervical mucus penetration-test (SCMPT) was performed. Sixty-five patients with primary infertility (mean age 29.9 y) completed the study. Compliance was assessed by microprocessor-based compliance monitoring. Besides compliance (percentage of prescribed doses taken), the adherence of the patients to the dosage schedule was evaluated — ‘regimen compliance’. The latter parameter of drug intake behaviour was calculated by the number of days in which 2 (BID) or 4 openings (QID) were recorded by the electronic monitor. As a third parameter, the deviation from the prescribed dosing intervals, i.e. 12 or 6 h, was also determined. Partial compliance was the predominant finding and only 9 patients (13.8%) were over-compliant. Mean compliance was 75.7% in all 65 patients as a group, range 7.1 to 143%. The mean compliance with the QID regimen was 67% compared to 85% with the BID regimen. ‘Regimen compliance’, the percentage of doses taken on schedule, was 36% and 63% for the QID and BID regimens, respectively. Drug-intake behaviour was more erratic with the QID than the BID regimen, as indicated by the 55% of opening intervals recorded which exceeded the range of 3–9 h (mean: 6 h), compared to only 19% exceeding 6–18 h intervals (mean: 12 h). The present study provides evidence that the prescribed dosage frequency has an impact on drug compliance by patients. From a practical point of view, it seems reasonable to use treatment regimens that are as simple as possible, provided that they are pharmacologically and clinically appropriate.