Failure to fill electronically prescribed antidepressant medications: a retrospective study.

Objective: Nonadherence to antidepressants has been reported to range widely from 10% to 60%. Most adherence studies focus on persistence of use and do not include prescriptions that are not picked up by the patient. The objectives of this study were to determine the rate of unfilled antidepressant prescriptions as well as to identify factors associated with failure to fill these prescriptions.

Method: This retrospective study used administrative and pharmacy data from a mid-Atlantic managed care organization serving 3.3 million medical members and 1.2 million pharmacy members. Electronic prescriptions for citalopram, duloxetine, sertraline, and venlafaxine sent to pharmacies from July 1, 2007, to June 30, 2009, were matched to pharmacy claims to determine the rate of unfilled antidepressant prescriptions. Patients were ≥18 years of age and had continuous pharmacy coverage from July 1, 2006, to July 31, 2009. Logistic regression was used to assess whether clinical and demographic factors were associated with unfilled electronic prescriptions.

Results: There were 557 electronically prescribed antidepressants for 267 patients. The rate of unfilled electronic prescriptions was 13.1%, which affected 19.9% of patients. Electronic prescriptions for new users of the antidepressant were 5 times more likely to be unfilled (odds ratio [OR]=5.13; 95% CI, 2.66-9.91; P<.001) than those for previous users. Antidepressant prescriptions for patients aged 18-34 years were most likely to be unfilled (OR=3.72; 95% CI, 1.81-7.67; P<.001).

Conclusions: Nonadherence to antidepressants is a significant problem with one-fifth of patients never receiving their electronically prescribed antidepressant. Prescriptions for patients without a previous antidepressant claim and aged 18-34 years were least likely to be filled. Interventions targeting patients who fail to fill their antidepressant prescription are needed.