carbidopa , an extracerebral inhibitor of l-aromatic amino acid decarboxylation , increased dose dependently the brain bioavailability of systemically administered 5-htp not only by peripheral enzyme inhibition , but also by inhibition of the decarboxylase activity within the blood-brain barrier as indicated by a rise in the calculated brain/plasma 5-htp concentration ratio .
C0006982
carbidopa
C2917347
inhibitor