Lack of counteracting effect of liposomes on benserazide-induced hyperprolactinemia.

Benserazide induces an increase of serum prolactin in man, possibly as the result of an impairment of the dopamine effect on the pituitary and/or on the outer median eminence caused by the inhibition on L-dopa decarboxylase. On the other hand, liposomes obtained from bovine brain cortex phospholipids reduced serum prolactin possibly through an effect of phosphatidylserine on dopamine biosynthesis at the level of tyrosine hydroxylase. Benserazide, given orally (125 mg) to 5 normal subjects, induced an increase of serum prolactin that did not change when 300 mg of phospholipid liposomes were given intravenously 60 min later. An increase of L-dopa synthesis does not seen to be capable to overcome the effects of the decarboxylase inhibition.