Full-Dose Distribution and Age-Dose Concordance of Suvorexant: A Retrospective Drug Utilization Study at a Japanese University Hospital.

The Japanese label specifies suvorexant 20 mg once nightly for adults and 15 mg once nightly for older adults, but dose selection has not been characterized across all doses. We conducted a single-center retrospective drug-utilization study of outpatient prescriptions and inpatient medication orders at a Japanese university hospital during 2023-2025. Dose and prescription-date age were reconstructed, and patient-cluster bootstrap confidence intervals addressed repeated prescriptions. Among 3755 records, 15 mg accounted for 68.4%, 20 mg for 29.9%, and 10 mg and other calculable doses each for 0.9%. Of 3685 age-classifiable 15/20 mg records, 2529 were concordant with the operational age-based framework (68.6%; 95% CI 62.5-74.2). Non-concordance predominantly comprised 15 mg in patients younger than 65 years (841/1646; 51.1%); 20 mg in patients aged 65 years or older occurred in 315/2039 records (15.4%). Concordance was 65.0% in outpatient and 73.8% in inpatient records. Full-dose retention revealed uncommon 7.5- and 30-mg selections that a binary analysis would omit. Together, these findings provide a descriptive, single-center, full-dose, age- and setting-stratified basis for medication-use evaluation and targeted contextual review.