LAUSR

Abstract It has remained unclear what factors relate to primary nonadherence to antipsychotic treatment and whether specific agents and routes of administration differ in how patients adhere to them. We collected electronic prescriptions and their dispensings from the Finnish electronic prescription database for 29 956 patients with schizophrenia prescribed antipsychotics via electronic prescription during 2015–2016. We defined primary nonadherence as being prescribed an antipsychotic, which was not dispensed from the pharmacy within one year from prescription. Using logistic regression, we analyzed whether several sociodemographic and clinical factors related to nonadherence. We found that 31.7% (N = 9506) of the patients demonstrated primary nonadherence to any of their prescribed antipsychotics. We found that young age (OR = 1.77, 95%CI = 1.59–1.96), concomitant benzodiazepines (OR = 1.47, 95%CI = 1.40–1.55) and mood stabilizers (OR = 1.29, 95%CI = 1.21–1.36), substance abuse (OR = 1.26 95%CI = 1.19–1.35), previous suicide attempt (OR = 1.21, 95%CI = 1.11–1.31), diabetes (OR = 1.15, 95%CI = 1.06–1.25), asthma/COPD (OR = 1.14, 95%CI = 1.04–1.25), and cardiovascular disease (OR = 1.12, 95%CI = 1.05–1.19), were related to primary nonadherence to antipsychotic treatment. Patients using clozapine showed the lowest nonadherence (4.77%, 95%CI = 4.66–4.89), and patients using long-acting injectables were more adherent to treatment (7.27%, 95%CI = 6.85–7.71) when compared to respective oral agents (10.26%, 95%CI = 10.02–10.49). These results suggest that selection between different pharmacological agents and routes of administration while taking into account patients’ concomitant medications (benzodiazepines in particular) and comorbidities play a key role in primary nonadherence to antipsychotic treatment.