Interactions of levodopa with inhibitors of monoamine oxidase and L-aromatic amino acid decarboxylase.

Drug interactions between levodopa, tranylcypromine, and carbidopa have been studied in 4 patients with idiopathic parkinsonism. Pressor responses were induced by a combination of levodopa and tranylcypromine. These hypertensive reactions were inhibited by carbidopa, indicating that they are mediated at the periphery. Very small doses of levodopa induced an improvement in parkinsonism when patients were concomitantly taking carbidopa and tranylcypromine, but adverse reactions were prominent.