title: Analgesic response to morphine in obese and morbidly obese patients in the emergency department.
abstract: OBJECTIVE
  The primary objective of this study was to compare the analgesic response to morphine in non-obese, obese and morbidly obese patients for acute pain.
  
  
  METHODS
  This was a retrospective cohort study conducted in a tertiary care emergency department in the USA. Consecutive adults who received intravenous morphine 4 mg for pain were included. Patients were categorised into three groups based on body mass index (BMI): non-obese (18.5-29.9 kg/m(2)); obese (30.0-39.9 kg/m(2)); and morbidly obese (≥40 kg/m(2)). Baseline and post-dose pain scores were recorded. Pain was measured on a 0-10 numerical rating scale (0=no pain; 10=worst possible pain). Analgesic response was defined as the difference between the initial pain score and post-dose pain score.
  
  
  RESULTS
  300 patients were included in the study (100 in each group). The median baseline pain scores were 8.5, 8 and 8.5 in the non-obese, obese and morbidly obese groups, respectively (p=0.464). The median analgesic response after morphine administration was 2, 3 and 2 in the non-obese, obese and morbidly obese groups, respectively (p=0.160). In the linear regression analysis (R(2)=0.006), BMI was not predictive of analgesic response (coefficient -0.020; p=0.199).
  
  
  CONCLUSIONS
  Obesity status did not influence analgesic response to a fixed dose of morphine. This suggests that obese and morbidly obese patients do not require a higher dose of morphine for acute pain reduction compared to non-obese patients.
authors: Department of Pharmacy Practice & Science, College of Pharmacy, University of Arizona, , Tucson, Arizona, USA.
authors: Asad E
authors: AE
authors: Patanwala
authors: Karen L
authors: KL
authors: Holmes
authors: Brian L
authors: BL
authors: Erstad
mesh_terms: D059787:Acute Pain / Q000188:drug therapy*; D061605:Administration, Intravenous; D000328:Adult; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D015992:Body Mass Index; D004636:Emergency Service, Hospital; D006801:Humans; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000627:therapeutic use*; D009767:Obesity, Morbid; D010147:Pain Measurement; D012044:Regression Analysis; D012189:Retrospective Studies; D014481:United States
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine
keywords: Analgesia/Pain Control; Emergency Department