Adherence to study medication and visits: data from the BABY HUG trial

Abstract

Background: Subject retention and adherence are essential to maintain the power and validity of the Pediatric Hydroxyurea Phase III Clinical Trial (BABY HUG). We designed a study to assess adherence with study medication administration and study visits and to evaluate socioeconomic factors (SES) that may influence these measurements of adherence. These data are important for assessing impact of adherence on BABY HUG trial outcome and defining impact of SES on adherence.

Methods: Each subject's median study medication (MedAd) and mean visit adherence (VAd) were evaluated. We examined associations of adherence with SES of participating families.

Results: MedAd data were available on 153 of the 191 subjects who started randomized study medication. MedAd was 101.7% of volume prescribed, with 88.9% of subjects taking at least 80% of doses. VAd data were available on 185 of the 191 subjects who started randomized study medication. VAd was 97.3%, with 82.2% of subjects having no missed visits. During dose titration, subjects had on average 12.9% higher medication adherence than subjects who were on a stable dose and had less frequent study visits. MedAd and VAd were not significantly associated with SES.

Conclusion: Subjects in the BABY HUG trial have had excellent adherence. SES was not associated with adherence, suggesting that SES should not be used as a criterion for enrolment in clinical trials. Additional efforts are needed to maintain medication adherence, particularly when the interval between scheduled visits increases. (ClinicalTrials.gov number, NCT00006400).

Conflict of interest statement

DISCLOSURE STATEMENT

The authors have no relevant conflict of interest related to this manuscript.

(c) 2009 Wiley-Liss, Inc.

Figures

Figure 1. Flowchart of subjects included in the medication adherence and visit adherence analysis

The flowchart indicates which subjects were included in the MedAd and VAd analyses. Study status is indicated for subjects that were and were not included in each analysis. *Subjects were not included in MedAd analysis if they had <10 occasions when a bottle was dispensed at a visit, returned at the next scheduled visit (with a non-zero volume), and no medication stop order occurred between the visits. **Subjects were not included in VAd analysis if they had a genotype other than HbSS or when all study visits were at a non-stable dose.

Figure 2. Study medication adherence over the course of the BABY HUG trial

The boxplots indicate the distribution of MedAd (%) at 0.5, 1, 1.5, and 2 years after the initiation of study medication. The horizontal line indicates 100% MedAd.