Tolmetin sodium in the management of nephrogenic diabetes insipidus

A Rare Case of Congenital Diabetes Insipidus

Congenital nephrogenic diabetes insipidus (NDI) is a conformation disease resulting from protein misfolding. Ninety percent of mutations result from the inactivating mutations of the arginine vasopressin receptor 2 (AVPR2) gene transmitted in an X-linked fashion, blocking the response to vasopressin, resulting in the inability to concentrate urine. Clinical features include polyuria, polydispsia, dehydration, and hypernatremia. They are generally more severely in affected males but present variably in females due to skewed inactivation of the X chromosome. We describe a case of a 40-year-old woman with a history of Type 2 diabetes mellitus, hyperlipidemia, and obesity, who presents with debilitating polyuria since the age of 5 with no clear diagnosis. Interestingly, her son was diagnosed with NDI. Genetic testing revealed that she was heterozygous for the Val88Met mutation in the AVPR2 gene while her son was hemizygous for the same. The patient has since been successfully treated with diuretics and a low solute diet. We highlight that although X-linked NDI patients are mostly males, it should be considered in symptomatic females to prevent delays in the diagnosis. Conformational diseases such as NDI are presently the subject of research using pharmacological chaperones to restore proper receptor membrane localization and function.

Clinical aspects of renal prostaglandins and NSAID therapy

Nonsteroidal antiinflammatory drugs (NSAIDs) can have a variety of effects on renal function. Excluding allergic phenomena, these are directly related to NSAID-induced inhibition of renal synthesis of prostaglandins (PGs). For the most part, renal PGs play important physiological roles only in certain pathologic conditions. Thus, patients without these diseases (such as cardiac, hepatic, or renal compromise) manifest no or only trivial effects on renal function when NSAIDs are administered. This feature is to the advantage of the clinician because it allows prospective identification of patients who are at risk for an adverse renal effect; hence, such effects can be minimized or avoided altogether. To do so requires an understanding of the various roles of PGs in the kidney and thereby the effects that one can observe from NSAIDs. This review focuses on these various roles of renal PGs and on identification of patient groups at risk for adverse renal effects of NSAIDs.

Treatment of nephrogenic diabetes insipidus with prostaglandin synthesis inhibitors

The antidiuretic effect of two prostaglandin synthetase inhibitors, ibuprofen (25 mg/kg/day) and indomethacin (2 mg/kg/day), was studied in patients aged 8 to 18 years with hereditary nephrogenic diabetes insipidus. Ibuprofen (studied in five patients) did not have demonstrable effects on urine volume, free water clearance, or osmolar clearance, but fractional excretion of sodium decreased from a mean of 0.38% to 0.19% (P less than 0.05). In contrast, indomethacin (studied in three patients) was associated with a decrease in mean urine volume from 5.8 to 2.8 mL/min and a decrease in mean free water clearance from 3.1 to 1.1 mL/min (both P less than 0.05). Fractional excretion of sodium decreased from 0.77% to 0.27% (P less than 0.01) and was accompanied by an increase in serum urea nitrogen level (P less than 0.01) and a decrease in urea nitrogen clearance (P less than 0.025). Thus, prostaglandin synthetase inhibitors are not uniformly effective in treatment of nephrogenic diabetes insipidus. The inhibitory effect of indomethacin on urine volume and free water clearance in our patients may have been mediated by an enhancement of antidiuretic hormone (ADH)-stimulated cyclic adenosine monophosphate generation, or by increased ADH-independent water reabsorption resulting from an increase in solute reabsorption and consequent medullary hypertonicity.