Chlorpropamide has been shown to be an effective oral therapy in diabetes insipidus of hypothalamic-pituitary origin. In some cases with anterior pituitary dysfunction, although chlorpropamide was antidiuretic, hypoglycaemia was a barrier to continued therapy. Tests indicated that chlorpropamide does not produce this effect by a reduction in glomerular filtration rate nor by increasing vasopressin secretion, nor by acting like the thiazide diuretics in diabetes insipidus but is more likely to act by increasing the sensitivity of the renal tubule to low and otherwise ineffective concentrations of vasopressin.