The effect of nalbuphine on gastrointestinal transit in mice

Nalbuphine given subcutaneously (s.c.) inhibited gastrointestinal transit in a dose-dependent manner. Prior s.c. administration of naloxone hydrochloride suppressed the inhibitory effect of nalbuphine on gastrointestinal transit. Naloxone methobromide (naloxone MB), a quaternary compound, was also effective in antagonising this effect of nalbuphine but was less effective than naloxone hydrochloride. Furthermore, prior s.c. administration of Mr 2266 also antagonised the gastrointestinal transit inhibitory action of nalbuphine. When given centrally, either intracerebroventricularly (i.c.v.) or intracisternally (i.c.), naloxone hydrochloride was ineffective in antagonising s.c. nalbuphine. Similar findings were observed with centrally administered Mr 2266. In addition, i.c. nalbuphine had a minimal effect on gastrointestinal transit while i.c.v. nalbuphine only caused slight inhibition of gastrointestinal transit. It was concluded that nalbuphine inhibits gastrointestinal transit mainly through peripheral opiate receptors.