Clinical and biochemical effects of parachlorophenylalanine in a patient with the carcinoid syndrome.

Diarrhoea and skin flushing are characteristic features of the carcinoid syndrome. The diarrhoea is thought to be caused mainly by 5-hydroxytryptamine (5-HT) (Grahame-Smith, 1972) whereas the possible causes of the flushing attacks include bradykinin (Oates et al., 1964), prostaglandins (Sandler, Karim and Williams, 1968; Kaplan et al., 1973) 5-HT (Page and McCubbin, 1953) and noradrenaline and adrenaline (Schneckloth et al, 1957). The tryptophan 5-hydroxylase inhibitor parachlorophenylalanine (PCPA) has been shown to alleviate carcinoid diarrhoea and concurrently lower the urinary excretion of 5-hydroxyindole acetic acid (5-HIAA) (Engelman, Lovenberg and Sjoerdsma, 1967) but is reported to be of little or no value in the treatment of carcinoid flushing (Grahame-Smith, 1972; Marks, 1979). We report the clinical and biochemical features of a case in which a patient with the carcinoid syndrome was treated with PCPA and had an anomalous response with abolition of flushing attacks but no lessening of diarrhoea. Case report