Species differences in plasma protein binding of morphine and codeine
Baggot, J.D.; Davis, L.E.
American Journal of Veterinary Research 34(4): 571-574
1973
ISSN/ISBN: 0002-9645 PMID: 4632750 Document Number: 60940
The susceptibility or resistance of different species to morphine or its surrogates may be related to disposition factors that facilitate or prevent drug access to the target site. The extent of protein binding of carbon-14-morphine and carbon-14-codeine in plasma of different species was determined by the equilibrium dialysis technique and liquid scintillation counting. Independence of drug concentration and extent of protein binding were observed for both morphine and codeine. The extent of protein binding of labelled morphine and codeine was measured in plasma of goat, sheep, ox, horse, pony, swine, dog, cat, monkey, rat, rabbit, opossum, and man. The proportion of morphine bound to plasma proteins varied from 10.6% in swine to 23.6% in ox. In the majority of species, the binding of codeine was less than that of morphine.