To      : Marie Davis
Re      : Nubain (Nalbuphine)

Your question concerning the effects of Nubain(nalbuphine) arrived at an
unusual time. I am currently preparing a review article on anesthetic agents
and breastfeeding and had just started to review this drug.  Without going into
exhaustive detail,  nalbuphine interacts at the Kappa-3 opiate receptor rather
than the MU1 or MU2 receptor (like morphine).   The Kappa-3 receptor agonists
produce a spinal analgesia rather than the  central and peripheral analgesia
produced by other opiates.  What this all means is that one of the typical
responses to Kappa-3 analgesics is dysphoria or a psychotomimetic state
(disoriented and/or depersonalized feelings, hallucinations). Further, it is
metabolically cleared by the liver and feces,  not the kidney.  In newborns,
its clearance is probably slowed due to the poor hepatic metabolic state.  I
have not found the newborn half-life as of yet, but it is 2.2-2.6 hours in
adults.

So I'm wondering if the psychotomimetic state typical of Kappa receptor
agonists produces the symptoms you have seen in newborns, such as flaccid
muscles, poor suckling, etc ???

Back to my paper...

Tom Hale