Oral bioavailability of apomorphine in the rat with a portacaval venous anastomosis.

Orally administered apomorphine failed to produce stereotyped behavior in sham-operated rats, but did so following portacaval venous anastomosis. Brain and serum levels of apomorphine were highly correlated and corresponded with ratings of stereotypy. Tissue levels were undetectable after oral administration of apomorphine in intact rats but in shunted rats, were similar to those found after s.c. injection. These results suggest that a strong first-pass hepatic metabolism may account for the low oral bioavailability of catechol-aporphines.