Amiloride-induced hyponatremia

Pathophysiology of Drug-Induced Hyponatremia

Drug-induced hyponatremia caused by renal water retention is mainly due to syndrome of inappropriate antidiuresis (SIAD). SIAD can be grouped into syndrome of inappropriate antidiuretic hormone secretion (SIADH) and nephrogenic syndrome of inappropriate antidiuresis (NSIAD). The former is characterized by uncontrolled hypersecretion of arginine vasopressin (AVP), and the latter is produced by intrarenal activation for water reabsorption and characterized by suppressed plasma AVP levels. Desmopressin is useful for the treatment of diabetes insipidus because of its selective binding to vasopressin V2 receptor (V2R), but it can induce hyponatremia when prescribed for nocturnal polyuria in older patients. Oxytocin also acts as a V2R agonist and can produce hyponatremia when used to induce labor or abortion. In current clinical practice, psychotropic agents, anticancer chemotherapeutic agents, and thiazide diuretics are the major causes of drug-induced hyponatremia. Among these, vincristine and ifosfamide were associated with sustained plasma AVP levels and are thought to cause SIADH. However, others including antipsychotics, antidepressants, anticonvulsants, cyclophosphamide, and thiazide diuretics may induce hyponatremia by intrarenal mechanisms for aquaporin-2 (AQP2) upregulation, compatible with NSIAD. In these cases, plasma AVP levels are suppressed by negative feedback. In rat inner medullary collecting duct cells, haloperidol, sertraline, carbamazepine, and cyclophosphamide upregulated V2R mRNA and increased cAMP production in the absence of vasopressin. The resultant AQP2 upregulation was blocked by a V2R antagonist tolvaptan or protein kinase A (PKA) inhibitors, suggestive of the activation of V2R-cAMP-PKA signaling. Hydrochlorothiazide can also upregulate AQP2 in the collecting duct without vasopressin, either directly or via the prostaglandin E2 pathway. In brief, nephrogenic antidiuresis, or NSIAD, is the major mechanism for drug-induced hyponatremia. The associations between pharmacogenetic variants and drug-induced hyponatremia is an area of ongoing research.

Non-thiazide diuretics and hospitalization due to hyponatraemia: A population-based case-control study

OBJECTIVE

Diuretics are often implicated in hyponatraemia. While thiazides constitute one of the most common causes of hyponatraemia, data on loop diuretics and potassium-sparing agents are limited and partly conflicting. The objective of this investigation was to study the association between use of different types of non-thiazide diuretics and hospitalization due to hyponatraemia.

DESIGN, PATIENTS AND MEASUREMENTS

This was a register-based case-control study on the adult Swedish population. By linking national registers, patients hospitalized with a principal diagnosis of hyponatraemia (n = 11,213) from 1 October 2005 through 31 December 2014 were compared with matched controls (n = 44,801). Multivariable logistic regression, adjusted for multiple confounders, was used to analyse the association between use of diuretics and hyponatraemia. In addition, newly initiated use (≤90 days) and ongoing use were examined separately.

RESULTS

Adjusted odds ratios (aORs) (95% CI) were 0.61 (0.57-0.66) for the use of furosemide, 1.69 (1.54-1.86) for the use of amiloride and 1.96 (1.78-2.18) for the use of spironolactone and hospitalization due to hyponatraemia. For newly initiated therapy, aORs ranged from 1.23 (1.04-1.47) for furosemide to 3.55 (2.75-4.61) for spironolactone. The aORs for ongoing use were 0.52 (0.47-0.57) for furosemide, 1.62 (1.47-1.79) for amiloride and 1.75 (1.56-1.98) for spironolactone.

CONCLUSIONS

Ongoing use of furosemide was inversely correlated with hospitalization due to hyponatraemia, suggesting a protective effect. Consequently, if treatment with furosemide precedes the development of hyponatraemia by some time, other causes of hyponatraemia should be sought. Spironolactone and amiloride may both contribute to hyponatraemia; this effect is most prominent early in treatment.

Hyponatraemia and Moduretic-Grand Mal Seizures: A Review

Three cases are presented which emphasize the importance of hyponatraemia as a cause of grand mal seizures. The combination of hydrochlorothiazide and amiloride appears to increase the risk of hyponatraemia. We discuss the aetiology and treatment of hyponatraemia and review the necessity for such combination therapy. We recommend caution in prescribing diuretics and preparations such as Moduretic should be used only in those few patients shown to need potassium supplementation.

A systematic review and meta-analysis of thiazide-induced hyponatraemia: time to reconsider electrolyte monitoring regimens after thiazide initiation?

AIMS

Hyponatraemia is one of the major adverse effects of thiazide and thiazide-like diuretics and the leading cause of drug-induced hyponatraemia requiring hospital admission. We sought to review and analyze all published cases of this important condition.

METHODS

Ovid Medline, Embase, Web of Science and PubMed electronic databases were searched to identify all relevant articles published before October 2013. A proportions meta-analysis was undertaken.

RESULTS

One hundred and two articles were identified of which 49 were single patient case reports. Meta-analysis showed that mean age was 75 (95% CI 73, 77) years, 79% were women (95% CI 74, 82) and mean body mass index was 25 (95% CI 20, 30) kg m(-2) . Presentation with thiazide-induced hyponatraemia occurred a mean of 19 (95% CI 8, 30) days after starting treatment, with mean trough serum sodium concentration of 116 (95% CI 113, 120) mm and serum potassium of 3.3 (95% CI 3.0, 3.5) mm. Mean urinary sodium concentration was 64 mm (95% CI 47, 81). The most frequently reported drugs were hydrochlorothiazide, indapamide and bendroflumethiazide.

CONCLUSIONS

Patients with thiazide-induced hyponatraemia were characterized by advanced age, female gender, inappropriate saliuresis and mild hypokalaemia. Low BMI was not found to be a significant risk factor, despite previous suggestions. The time from thiazide initiation to presentation with hyponatraemia suggests that the recommended practice of performing a single investigation of serum biochemistry 7-14 days after thiazide initiation may be insufficient or suboptimal. Further larger and more systematic studies of thiazide-induced hyponatraemia are required.

Blood pressure drug therapy and electrolyte disturbances

Antihypertensive pharmacologic treatment may be associated with diverse disturbances of electrolyte homeostasis. These drug-induced disorders are relatively common, typically including hyponatraemia, hypokalaemia, hyperkalaemia, hypomagnesaemia, hypophosphataemia and hypercalcaemia. Diuretics, beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are particularly likely to cause these complications. Recognised risk factors include high-dosage regimens (especially diuretics), old age, diabetes and impairment of renal function. Strategies to prevent these adverse drug reactions involve careful consideration of risk factors and clinical and laboratory evaluation in the course of treatment.

The silent epidemic of thiazide-induced hyponatremia

Hyponatremia is a recognized complication of treatment with thiazide diuretics, particularly in patients older than 70 years. Severe and symptomatic hyponatremia requires urgent management, usually requiring infusion of normal or hypertonic saline. Milder, asymptomatic, thiazide-induced hyponatremia requires steps to manage the hyponatremia as well as to prevent its future recurrence. This is a particular problem in patients who despite a history of thiazide-induced hyponatremia might require a diuretic in the management of their hypertension. In this review, the acute management of symptomatic and asymptomatic thiazide-induced hyponatremia is reviewed. Emphasis is also placed on the chronic management of patients who have experienced mild hyponatremia, in whom decisions about treatment with diuretic and nondiuretic antihypertensive agents must be made to satisfy the twin goals of controlling hypertension and avoiding recurrent hyponatremia.

Diuretic-induced severe hyponatremia. Review and analysis of 129 reported patients

Thiazides were responsible for severe diuretic-induced hyponatremia (serum sodium level < 115 mEq/L) in 94 percent of 129 cases reported in the literature between 1962 and 1990. The hyponatremia developed within 14 days in most of the patients receiving thiazides but in none of the patients who were treated with furosemide. Diuretic-induced hyponatremia was four times more common in women than in men. Advanced age was not associated with a higher tendency for hyponatremia. In the majority of the patients who received thiazides, excess antidiuretic hormone activity, hypokalemia, and excess water intake were accompanying findings which, singly or together, appeared to contribute to the development of hyponatremia. In 12 patients, mortality was directly related to hyponatremia. Rapid average correction of hyponatremia and a relatively high total correction (over 20 mEq/L) in the first 24 h were significantly associated with higher mortality or demyelinating syndrome. The presence of neurologic signs is an indication for active sodium replacement. The onset of thiazide-induced hyponatremia may in some cases occur within 1 day and therefore needs to be corrected rapidly, but within a total elevation of 20 mEq/L in the first 24 h. Where the onset is judged to have been slow (over several days), the level should be corrected at a slow rate, up to a total of 12 to 15 mEq/L in 24 h.

Drug-induced electrolyte disorders

A wide variety of pharmacologic agents have been implicated in a number of electrolyte disorders. The present review focuses on abnormalities of sodium, potassium, calcium, magnesium, and phosphate. Several mechanisms are involved in the pathogenesis of these disorders. These involve stimulation and modulation of other hormones (e.g., antidiuretic hormone, renin-angiotensin system, parathyroid hormone), damage to renal tubules, and, in some cases, a combination of factors. Recognition of these abnormalities is important because their presence may be life threatening or may aggravate the side effects of the drug itself.