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Background Standard protocols or algorithms are considered essential to ensure adequate analgesia. Germany has widely adopted postoperative protocols for pain management including oral opioids for rescue medication, but the effectiveness of such protocols has only been evaluated longitudinally in a before and after setting. The aim of this cohort analysis was to compare the effectiveness of an oral opioid rescue medication algorithm for postoperative management of pain to the gold standard of patient-controlled intravenous analgesia (PCIA). Material and methods This study compared cohorts of patients of two prospective observational studies undergoing elective total hip replacement. After surgery patients received piritramide to achieve a pain score of ≤3 on the numeric rating scale (NRS 0–10). A protocol was started consisting of oral long-acting oxycodone and ibuprofen (basic analgesia). Cohort 1 (C1, 126 patients) additionally received an oral opioid rescue medication (hydromorphone) when reporting pain >3 on the NRS. Cohort 2 (C2, 88 patients) was provided with an opioid by PCIA (piritramide) for opioid rescue medication. Primary endpoints were pain intensity at rest, during movement, and maximum pain intensity within the first 24 h postoperative. Secondary endpoints were opioid consumption, functional outcome and patient satisfaction with pain management. Results Pain during movement and maximum pain intensity were higher in C1 compared to C2: pain on movement median 1st–3rd quartile: 6 (3.75–8) vs. 5 (3–7), p = 0.023; maximum pain intensity: 7 (5–9) vs. 5 (3–8), p = 0.008. There were no differences in pain intensity at rest or between women and men in either group. The mean opioid consumption in all patients (combined PACU, baseline, and rescue medication; mean ± SD mg ME) was 126.6 ± 51.8 mg oral ME (median 120 (87.47–154.25) mg ME). Total opioid consumption was lower in C1 than C2 (117 ± 46 mg vs 140 ± 56 mg, p = 0.002) due to differences in rescue opioids (C1: 57 ± 37 mg ME, C2: 73 ± 43 mg ME, p = 0.006, Z = −2.730). Basic analgesia opioid use was comparable (C1: 54 ± 31 mg ME, C2: 60 ± 36 mg ME, p = 0.288, Z = −1.063). There were no differences in respect to the addition of non-opioids and reported quality of mobilization, sleep, frequency of nausea and vomiting, or general satisfaction with pain management. Conclusion In this study PCIA provided a better reduction of pain intensity, when compared to a standardized protocol with oral opioid rescue medication. This effect was associated with increased opioid consumption. There were no differences in frequencies of opioid side effects. This study was a retrospective analysis of two cohorts of a major project. As with all retrospective studies, our analysis has several limitations to consider. Data can only represent the observation of clinical practice. It cannot reflect the quality of a statement of a randomized controlled trial. Observational studies do not permit conclusions on causal relationships.