Background: Analgesic treatment, including with opioids, can safely be given to patients who are suspected of having appendicitis. The study examined factors which may influence the treatment of pain in appendicitis in the adult emergency department (ED). A secondary objective was to determine if analgesia affected clinical outcomes.Methods: This single-center retrospective study examined medical records of all adult patients with a discharge diagnosis of appendicitis. Patients were categorized based on the type of analgesia received in the ED. Variables included the day of week and staffing shift of presentation, gender, age, and triage pain scale, as well as time to ED discharge, imaging, operation, and hospital discharge. Univariable and multivariable logistic regression models were performed to determine which factors influenced treatment and affected outcomes.Results: Records of 1839 patients were categorized into three groups - 883 (48%) did not receive analgesia, 571 (31%) received only non-opioid medications, and 385 (21%) received at least one opioid. Patients with a higher triage pain level were significantly more likely to receive analgesia (4-6: OR = 1.85; 95% CI = 1.2-2.84, 7-9: OR = 3.36; 95% CI = 2.18-5.17, 10: OR =10.78; 95% CI = 6.38-18.23) and at least one opioid (4-6: OR = 2.88; 95% CI = 1.13-7.34, 7-9: OR = 4.36; 95% CI = 1.73-11.01, 10: OR = 6.23; 95% CI = 2.42-16.09). Male gender was associated with a significantly lower likelihood of receiving analgesia (OR = 0.74; 95% CI = 0.61-0.9), but a significantly greater likelihood of receiving at least one opioid given that they re-ceived any pain medication (OR = 1.87; 95% CI = 1.41-2.48). Patients aged 25-64 years old were significantly more likely to receive at least one opioid if they received any pain medication (25-44: OR = 1.47; 95% CI = 1.08-2.02, 45-64: OR = 1.78; 95% CI = 1.15-2.76). Presentation to the ED on Sundays was associated with lower rates of opioid treatment (OR = 0.63; 95% CI = 0.42-0.94). Regarding clinical outcomes, patients who received analgesia waited longer for imaging (+0.58 h; 95% CI = 0.31-0.85), stayed longer in the ED (+2.2 h; 95% CI = 1.60-2.79), and had a slightly longer hospitalization (+0.62d; 95% CI = 0.34-0.90).Conclusions: Almost half of patients with appendicitis didn't receive analgesia, with most of those treated re-ceiving only non-opioid analgesia. Older age and Sunday presentations were associated with less opioid treatment. Patients who received analgesia waited longer for imaging, stayed longer in the ED, and had a longer hospitalization.& COPY; 2023 Elsevier Inc. All rights reserved.