Abstract
A modified Carter Robbins Test was used to diagnose central diabetes insipidus (DI) in 3 patients. After 2–3 months of oral chlorpropamide 250–500 mg/day, the test was repeated. In 2 patients CH2O remained negative even during a water load of 20 cc/kg and 2½% saline load of 10 cc/kg/45 min. There was no further drop of CH2O following 0.1 units aqueous pitressin intravenously. These and one other patient with DI were then subjected to a continuous water loading test initiated by giving 25 cc/kg of water while on chlorpropamide in a dose sufficient to cause antidiuresis without hypoglycemia. Water excretion was impaired in all patients. Serum Na fell at least 10 mEq/L in each patient. Serum osmolality fell 25 mosm/kg in 2 patients and fell 20 mosm/kg and 15 mosm/kg in the other 2 patients. All patients gained weight. Chloride spaces increased from 3% to 5% after the water load. CH2O remained negative throughout the entire test in 2 patients. A third patient developed a CH2O of +0.9 cc/min/1.73 m2. This maximum CH2O occurred 6½ hours after the water load. A fourth patient developed a CH2O of +25 cc/min/1.73 m2. This maximum CH2O occurred 2 hours after the water load, subsequently fell to .6 cc/min/1.73 m2 and never again exceeded +2.1 cc/min. Since published evidence indicates that chlorpropamide acts by potentiating ADH, our data suggests that the subthreshold circulating ADH presumed to be present in our patients is not further suppressed by water loading. Therefore, a potential danger exists for anyone taking chlorpropamide who either requires intravenous therapy, or who may drink a large amount of fluid.
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Linshaw, M., Sey, M., Digeorge, A. et al. Potential danger of chlorpropamide therahy: Impaired excretion of a water load. Pediatr Res 5, 392–393 (1971). https://doi.org/10.1203/00006450-197108000-00091
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DOI: https://doi.org/10.1203/00006450-197108000-00091