Background Pharmacological thromboprophylaxis is necessary among many hospitalised patients to prevent venous thromboembolism (VTE). However, a significant number of clinician-ordered doses are not administered with many doses refused by patients. We aimed to assess the impact and sustainability of a multifaceted intervention to improve medication adherence to pharmacological thromboprophylaxis. The intervention included a standardised nursing response to patient refusal, daily assessment of VTE prophylaxis usage and regular feedback on refusal rates.

Methods We conducted a quasi-experimental study of patients admitted between January 2010 and November 2012 to one of six hospital intervention units (three medical and three oncology units) or five control units. The primary outcome was the proportion of VTE prophylaxis doses missed for any reason.

Results A total of 20 208 admissions occurred at the six hospital units during the study period. In the pre-post analysis, the rate of missed and refused doses decreased significantly after the intervention (24.7% to 14.7% and 18.3% to 9.4%, respectively; p value <0.01 for both comparisons). In multiple regression models with interrupted time series analysis, the intervention was associated with an immediate and sustained decrease in missed (adjusted OR 0.64; 95% CI 0.55 to 0.74 and 0.98; 95%CI 0.97 to 0.99) and refused doses (adjusted OR per month 0.58; 95% CI 0.48 to 0.71 and 0.97; 95%CI 0.96 to 0.98). No immediate or sustained reduction in missed or refused doses was observed in the control units.

Conclusions Implementation of a multifaceted intervention resulted in an immediate and sustained decrease in the proportion of missed and refused doses of pharmacological thromboprophylaxis. Efforts aimed at increasing patient adherence are a promising approach to improve rates of VTE thromboprophylaxis administration.