Potentiation of small cell lung cancer-related SIADH by trifluoperazine.

The syndrome of inappropriate anti-diuretic hormone secretion (SIADH) is a feature of approximately 7% of cases of small cell lung cancer (SCLC). The elaboration of peptide hormones by this tumour is well recognised and cerebral oedema resulting from inappropriate ADH secretion may be a life-threatening complication of this illness, requiring prompt intervention. We report a patient with SCLC who presented with SIADH which worsened abruptly each time he was treated with trifluoperazine for a co-existing psychosis.