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dxm differential potentiation of opioid analgesics

dxm differential potentiation of opioid analgesics

  1. Ilsa
    Opioid drugs such as morphine and meperidine are widely used in clinical pain management,
    although they can cause some adverse effects. A number of studies indicate that N-methyl-D-aspartate
    (NMDA) receptors may play a role in the mechanism of morphine analgesia, tolerance and
    dependence. Being an antitussive with NMDA antagonist properties, dextromethorphan (DM) may
    have some therapeutic benefits when coadministered with morphine. In the present study, we
    investigated the effects of DM on the antinociceptive effects of different opioids. We also investigated
    the possible pharmacokinetic mechanisms involved.
    2 The antinociceptive effects of the m-opioid receptor agonists morphine (5 mgkg1, s.c.), meperidine
    (25mg kg1, s.c.) and codeine (25mg kg1, s.c.), and the k-opioid agonists nalbuphine (8 mgkg1, s.c.)
    and U-50,488H (20mg kg1, s.c.) were studied using the tail-flick test in male Sprague–Dawley rats.
    Coadministration of DM (20mg kg1, i.p.) with these opioids was also performed and investigated.
    3 The pharmacokinetic effects of DM on morphine and codeine were examined, and the free
    concentration of morphine or codeine in serum was determined by HPLC.
    4 It was found that DM potentiated the antinociceptive effects of some m-opioid agonists but not
    codeine or k-opioid agonists in rats. DM potentiated morphine’s antinociceptive effect, and acutely
    increased the serum concentration of morphine. In contrast, DM attenuated the antinociceptive effect
    of codeine and decreased the serum concentration of its active metabolite (morphine).
    5 The pharmacokinetic interactions between DM and opioids may partially explain the differential
    effects of DM on the antinociception caused by opioids.
    British Journal of Pharmacology (2005) 144, 400–404. doi:10.1038/sj.bjp.0706086