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It has been suggested that the dose of intravenous morphine used during postoperative titration is not modified by aging. The authors therefore studied morphine requirements in patients undergoing total hip replacement.Intravenous morphine titration was administered as boluses, then subcutaneous morphine was administered every 4 h over 24 h. Pain was assessed by use of the visual analog scale (0 to 100), and the threshold required to administer morphine was 30. Young and elderly (≥70 yr old) patients were compared. Data are mean ± SD or odds ratio (OR) [95% CI].Two hundred twenty-four patients (68%) were young and 105 (32%) were elderly. The initial visual analog scale was not significantly different between groups. The dose of intravenous morphine in the postanesthesia care unit was not significantly different between young and elderly patients (0.15 ± 0.11 vs. 0.14 ± 0.10 mg/kg, P = NS), in contrast to the dose of subcutaneous morphine (0.18 ± 0.18 vs. 0.11 ± 0.11 mg/kg, P < 0.001) in the ward. Only severe pain (visual analog scale of 70 or greater; OR, 10.5 [4.5–24.8]) was significantly associated with a high dose (greater than 0.15 mg/kg) of intravenous morphine, whereas severe pain (OR, 2.5 [1.6–4.0]), age less than 60 yr (OR, 2.3 [1.4–3.8]), and absence of a nonsteroidal antiinflammatory drug (OR, 1.9 [1.2–3.1]) were significantly associated with a high dose (greater than 0.12 mg/kg) of subcutaneous morphine.The dose of intravenous morphine during titration is not modified in elderly patients, in contrast to the dose administered subcutaneously over a prolonged period.