INTRODUCTION. Acute post-operative pain treatment continues to pose a primary therapeutic challenge for clinicians, particularly in opioid-tolerant patients. The purpose of this study was to examine whether patients with a high total daily intake of long-acting opioids received the recommended PRN opioid doses in the first 24 hours after surgery. METHODS. This was a retrospective cohort study using a comprehensive hospital database at the Aarhus University Hospital, Denmark. Patients who received both slow-release long-acting and PRN opioids within the first 24 hours after inpatient surgery were included. Patients were defined as having a high intake if they received slow-release opioids ≥ 60 mg morphine equivalents (MME). RESULTS. In total, 199 patients (14%) received a 24-hour dose of slow-release long-acting opioids ≥ 60 MME and 1,247 patients (86%) received < 60 MME. The median age was 64 years (interquartile range: 49-74 years); 54% were female. Patients in the ≥ 60 MME group were less likely to receive the recommended first PRN dose (at least 10% of total 24-hour dose) within the first 24 hours after surgery (79 patients; proportion = 0.40, 95% confidence interval (CI): 0.33-0.47 versus 129 patients; proportion = 0.10, 95% CI: 0.09-0.12, p < 0.001). CONCLUSIONS. Our results suggest that patients with a high intake of long-acting opioids may be more likely to receive PRN opioid doses that are not sufficiently adjusted to their total intake during the first 24 hours after inpatient surgery than patients with a lower intake of long-acting opiods.