Perineural antinociceptive effect of opioids in a rat model.
BACKGROUND
The research on conductive analgesia induced by perineural opioids generated a large body of conflicting data. In this study we reassessed the antinociceptive response to perineural administration of morphine, fentanyl or meperidine in a rat model.


METHODS
Analgesia was assessed using the hind paw withdrawal latency (HPWL) response to radiant heat. The opioid dose producing 20% of maximal possible effect (20%MPE) for systemic analgesia was calculated for each drug. Then sciatic blockade was performed with the dose corresponding to 20%MPE. The injected hind paw was used to measure direct perineural effect and the contralateral hind paw was used as an indicator of systemic effect.


RESULTS
The response latency produced by morphine or fentanyl was not significantly different for ipsilateral (perineural effect) or contralateral (systemic effect) paw (27+/-11 vs. 28+/-16 and 3l+/-16 vs. 23+/-16 s, respectively). However, the meperidine group showed significantly higher %MPE for the ipsilateral paw (79+/-32 s) than for the contralateral paw (27+/-22 s).


CONCLUSIONS
The results indicate that perineural fentanyl or morphine do not produce analgesia. Perineural block produced by meperidine was attributed to local anesthetic-like effect, rather than to drug interaction with opioid receptor.
Grant
G J
GJ
Department of Anesthesiology, New York University Medical Center, New York, USA.
Vermeulen
K
K
Zakowski
M I
MI
Langerman
L
L
D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005283:Fentanyl / Q000494:pharmacology; D008297:Male; D008614:Meperidine / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology; D009407:Nerve Block; D010147:Pain Measurement / Q000187:drug effects; D010525:Peripheral Nerves / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000187:drug effects
D000701:Analgesics, Opioid; D009020:Morphine; D008614:Meperidine; D005283:Fentanyl