Antidepressant nonadherence in routine clinical settings determined from discarded blood samples

Antidepressant nonadherence is common and represents a potentially modifiable risk factor for treatment nonresponse. We used a novel approach based on discarded blood samples from routine clinical blood draws to assess treatment nonadherence in a general clinical population.

Individuals diagnosed with or without major depressive disorder (using ICD-9) and prescribed sertraline, citalopram, bupropion, or venlafaxine in January 2014 were identified by querying the electronic health record of 2 academic medical centers. Discarded blood samples from routine blood draws for 109 individuals within 14-90 days of treatment initiation were anonymized and then assessed for detectable serum antidepressant levels.

Overall, 17% of samples lacked detectable levels of the index antidepressant. Individuals with public versus private insurance were more likely to have undetectable antidepressant levels (χ(2)1 = 5.07, P = .02) as were those receiving shorter-term (< 90 days) prescriptions (χ(2)1 = 4.03, P = .05).

In general, electronic prescribing data provided a reasonable proxy for actual antidepressant use. Additionally, up to 1 in 5 individuals prescribed an antidepressant may not be adherent, suggesting the need for further efforts to reduce treatment nonadherence.