Oral naloxone reduces constipation but not antinociception from oral morphine in the rat

Oral administration of naloxone (10 mg/kg) antagonized the slowing of the intestinal transit caused by oral morphine (1, 2.5 and 5 mg/kg) in rats. Oral administration of naloxone (10 mg/kg) did not prevent the antinociceptive effect of orally administered morphine (2.5 mg/kg) in the tail-flick test...

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Bibliographic Details
Published inNeuroscience letters Vol. 142; no. 1; p. 62
Main Authors Jurna, I, Kaiser, R, Kretz, O, Baldauf, J
Format Journal Article
LanguageEnglish
Published Ireland 03.08.1992
Subjects
Administration, Oral
Animals
Constipation - physiopathology
Constipation - prevention & control
Gastrointestinal Transit - drug effects
Male
Morphine - pharmacology
Naloxone - pharmacology
Naloxone - therapeutic use
Nociceptors - drug effects
Pain Measurement
Rats
Rats, Sprague-Dawley
Reaction Time
Tail
Time Factors
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Summary:Oral administration of naloxone (10 mg/kg) antagonized the slowing of the intestinal transit caused by oral morphine (1, 2.5 and 5 mg/kg) in rats. Oral administration of naloxone (10 mg/kg) did not prevent the antinociceptive effect of orally administered morphine (2.5 mg/kg) in the tail-flick test carried out on rats. It is concluded that oral naloxone locally blocks the constipating effect of morphine, while it fails to reduce the central action of morphine due to extensive metabolization after oral administration.
ISSN:0304-3940
1872-7972
DOI:10.1016/0304-3940(92)90620-M