Primary Non-Adherence to Electronic Prescriptions in Lithuania, 2018–2024: Nationwide Prevalence, Factors, and Regional Variation

Background/Objectives: Primary non-adherence occurs when a prescribed medicine is never collected, preventing treatment from the beginning. Despite non-adherence being a widespread problem, most evidence comes from Western European and North American systems, and the Baltic region has rarely been assessed. Using Lithuania’s nationwide e-prescription system, we estimated primary non-adherence, identified associated factors, and characterised regional variation. Methods: We conducted a nationwide study of all outpatient electronic prescriptions issued in Lithuania, 2018–2024. We used open, anonymised quarterly prescribing and dispensing records from the national e-prescription subsystem and the national e-Health Services and Cooperation Infrastructure Information System (ESPBI IS). Prescribing and dispensing were deterministically linked. Prescriptions were classified as completed (dispensed quantity ≥ 90% of that prescribed), partially completed (dispensed quantity > 0% but <90%), or not completed (no quantity dispensed, defining primary non-adherence). Logistic regression estimated associations with patient, prescriber, prescription, and geographic characteristics; the results are reported as adjusted odds ratios (aOR) with 99% confidence intervals. Results: Of 108,204,007 prescriptions, 10.0% were never dispensed. Primary non-adherence was strongly associated with non-reimbursed status (aOR 3.47, 99% CI 3.46–3.48), younger age (18–44 years: 19.2% vs. ≥65 years: 7.0%), and short-term treatment (≤30 days: 14.1% vs. >90 days: 5.7%). Primary non-adherence rates were highest in cities (11.8%) and concentrated in the Vilnius metropolitan area (15.3%) and lowest in rural municipalities (5.5–6.0%). Conclusions: One in ten Lithuanian prescriptions is never dispensed. Non-adherence showed a marked, persistent geographic variance, with higher rates centred around Vilnius. Reimbursement status was the dominant correlate, pointing to cost as a key lever at the point of initiation.