Assessment of SIADH in psychosis with a water-loading test: case report.

A man taking haloperidol presented with psychosis, polydipsia, and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). A water-loading test indicated that haloperidol did not cause the SIADH. In patients taking haloperidol or other neuroleptics associated with SIADH who develop psychosis, polydipsia, and complications of SIADH such as hyponatremia, water loading may be helpful in adjusting psychotropic medications so as to control psychosis while avoiding the complications of hyponatremia.