Morphine vs. Oxycodone for Postoperative Pain Management
Condition: Hysterectomy; Myoma; Postoperative Pain; Opioids
MeSH terms: Pain, Postoperative
Study type: Interventional
Phase: Phase 4

Summary: 
      The purpose of this study is to determine whether oxycodone provides better analgesia
      compared to morphine after laparoscopic hysterectomy or myomectomy.
    

Detailed description: 
      Traditionally, a 1:1 ratio in analgesic potency between intravenous morphine and oxycodone
      has been presumed (1-2), but one study demonstrated a 3:2 ratio between those drugs (3).
      During the last years, several studies indicate that oxycodone has the potential of mediating
      pain relief through the kappa-opioid receptor (4-6), and not only on the my-opioid receptor
      like most other opioids used in the clinic. Kappa-opioid receptors are widely distributed in
      visceral organs, and this may explain why Kalso (3) found less need for oxycodone compared to
      morphine in patients undergoing abdominal surgery.

      The aim of this study is to investigate whether patients with visceral postoperative pain
      need less oxycodone compared to morphine, and whether patients receiving oxycodone experience
      better pain relief and less adverse effects compared to patients receiving morphine.

      Before start of surgery, the patients will be tested with PainMatcher, an instrument testing
      electrical pain threshold in the skin (7-10), to ensure that both groups have the same pain
      threshold before surgery.

      References

        1. Kalso E. Oxycodone. Journal of Pain & Symptom Management 2005; 29: S47-S56.

        2. Silvasti M, Rosenberg P, Seppala T, Svartling N, Pitkanen M. Comparison of analgesic
           efficacy of oxycodone and morphine in postoperative intravenous patient-controlled
           analgesia. Acta Anaesthesiol Scand 1998; 42: 576-80.

        3. Kalso E, Poyhia R, Onnela P, Linko K, Tigerstedt I, Tammisto T. Intravenous morphine and
           oxycodone for pain after abdominal surgery. Acta Anaesthesiol Scand 1991; 35: 642-6.

        4. Staahl C, Christrup LL, Andersen SD, Arendt-Nielsen L, Drewes AM. A comparative study of
           oxycodone and morphine in a multi-modal, tissue-differentiated experimental pain model.
           Pain 2006; 123: 28-36.

        5. Ross FB, Smith MT. The intrinsic antinociceptive effects of oxycodone appear to be
           kappa-opioid receptor mediated. Pain 1997; 73: 151-7.

        6. Sandner-Kiesling A, Pan HL, Chen SR, James RL, Haven-Hudkins DL, Dewan DM, Eisenach JC.
           Effect of kappa opioid agonists on visceral nociception induced by uterine cervical
           distension in rats. Pain 2002; 96: 13-22.

        7. Alstergren P, Forstrom J, Alstergren P, Forstrom J. Acute oral pain intensity and pain
           threshold assessed by intensity matching to pain induced by electrical stimuli. Journal
           of Orofacial Pain 2003; 17: 151-9.

        8. Lundeberg T, Lund I, Dahlin L, Borg E, Gustafsson C, Sandin L, Rosen A, Kowalski J,
           Eriksson SV. Reliability and responsiveness of three different pain assessments. Journal
           of Rehabilitation Medicine 2001; 33: 279-83.

        9. Nielsen PR. Prediction of post-operative pain by an electrical pain stimulus. Acta
           Anaesthesiol Scand 2007; 51: 582-6.

       10. Stener-Victorin E, Kowalski J, Lundeberg T. A new highly reliable instrument for the
           assessment of pre- and postoperative gynecological pain. Anesth & Analg 95: 151-7.
    

Intervention name(s): Morphine and oxycodone
Intervention type(s): Drug
Intervention description(s): At the end of surgery, group 1 will receive intravenous morphine 0.07 mg/kg and intravenous PCA morphine 0.015 mg/kg every time they push the botton with 5 minutes lock-out interval. Maximum 16 mg/2 hours. Group 2 will receive intravenous oxycodone 0.07 mg/kg and intravenous PCA oxycodone 0.015 mg/kg every time they push the botton with 5 minutes lock-out interval. Maximum 16 mg/2 hours.
The patients will use the PCA until the next morning.
Intervention MeSH terms: Morphine; Oxycodone
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Care Provider, Investigator)
Primary purpose: Treatment
Keywords: kappa-opioid receptor; my-opioid receptor; oxycodone; morphine; postoperative pain