A clinical and biochemical study of monoamine oxidase inhibition in depressed patients. II. 5-Hydroxytryptamine tolerance before and after Nialamide.
Summary Extracerebral monoamine oxidase activity was assessed by a 5-hydroxy tryptamine tolerance test in 18 depressed patients and 2 normal controls before and after treatment with an amine oxidase inhibitor (Nialamide). Some patients showed a considerable reduction of 5-HIAA excretion after receiving the drug but none of these showed any clinical improvement in their depression. Conversely one patient improved on the drug but showed no evidence of monoamine oxidase inhibition. The validity of the 5-hydroxytryptamine tolerance test as an indicator of cerebral monoamine oxidase activity is discussed.