Adherence pattern to study drugs in clinical trials by patients with cystic fibrosis

Background Clinical trials are all based on the assumption that patients are adherent to the study protocol. Many reports indicate that general adherence of patients with CF to their daily routine therapies is poor. However, no data exists on adherence to study drug regimens. Methods All clinical trials carried out at the Hadassah CF Center from 2008 to 2013 were reviewed. Actual adherence as determined by counted drugs was analyzed according to drug administration mode, study lengths and number of study visits. A subset of patients answered a two-part questionnaire covering study specific and general treatment specific issues. Results Eight studies including 118 patients, with patient numbers varying between 4 and 32 per trial were analyzed. For 7/8 studies mean adherence was between 78% to 100%. Comparison with administration mode showed that adherence decreased substantially if the drugs were not provided as "ready to be used" (63%). Study length influenced adherence, the longer the study the poorer the adherence (82% trial beginning, 44% post 36 months [two combined studies with identical drug]). A substantial decrease was noted over Holiday periods and during the summer vacation months. No correlation was found between number of study visits and adherence to study drug. Conclusion Adherence to study drug is generally higher than that for regular treatment. Study length, mode of administration, and timing according to Holidays and vacations adversely affect adherence.