Hyponatraemia due to the combination of hydrochlorothiazide and amiloride (Moduretic): Australian spontaneous reports 1977-1988

Acetazolamide Attenuates Lithium-Induced Nephrogenic Diabetes Insipidus

To reduce lithium-induced nephrogenic diabetes insipidus (lithium-NDI), patients with bipolar disorder are treated with thiazide and amiloride, which are thought to induce antidiuresis by a compensatory increase in prourine uptake in proximal tubules. However, thiazides induced antidiuresis and alkalinized the urine in lithium-NDI mice lacking the sodium-chloride cotransporter, suggesting that inhibition of carbonic anhydrases (CAs) confers the beneficial thiazide effect. Therefore, we tested the effect of the CA-specific blocker acetazolamide in lithium-NDI. In collecting duct (mpkCCD) cells, acetazolamide reduced the cellular lithium content and attenuated lithium-induced downregulation of aquaporin-2 through a mechanism different from that of amiloride. Treatment of lithium-NDI mice with acetazolamide or thiazide/amiloride induced similar antidiuresis and increased urine osmolality and aquaporin-2 abundance. Thiazide/amiloride-treated mice showed hyponatremia, hyperkalemia, hypercalcemia, metabolic acidosis, and increased serum lithium concentrations, adverse effects previously observed in patients but not in acetazolamide-treated mice in this study. Furthermore, acetazolamide treatment reduced inulin clearance and cortical expression of sodium/hydrogen exchanger 3 and attenuated the increased expression of urinary PGE2 observed in lithium-NDI mice. These results show that the antidiuresis with acetazolamide was partially caused by a tubular-glomerular feedback response and reduced GFR. The tubular-glomerular feedback response and/or direct effect on collecting duct principal or intercalated cells may underlie the reduced urinary PGE2 levels with acetazolamide, thereby contributing to the attenuation of lithium-NDI. In conclusion, CA activity contributes to lithium-NDI development, and acetazolamide attenuates lithium-NDI development in mice similar to thiazide/amiloride but with fewer adverse effects.

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.

Risk factors for thiazide-induced hyponatraemia

BACKGROUND

Thiazide-induced hyponatraemia is common and potentially life threatening. In the absence of well-defined risk factors for this complication, guidelines for prescribing cannot be established.

AIM

To examine whether a subgroup of patients is particularly susceptible to this complication.

DESIGN

Retrospective case-control study.

METHODS

We defined and recruited cases of symptomatic hyponatraemia that necessitated hospitalization from January 1996 to April 2002. Controls were selected from 8420 patients being prescribed thiazides and seen at the same institution during that period of time.

RESULTS

There were 223 cases and 216 controls, with a median 115 days thiazide use. Cases were older than controls (76 +/- 9 vs. 66 +/- 13 years, p < 0.001) and lighter (52.3 +/- 10.3 vs. 63.4 +/- 3 kg, p < 0.001). By univariate analysis, serum potassium level, use of indapamide, elderly home institutionalization and physical immobility were risk factors for thiazide-induced hyponatraemia, but gender, duration of thiazide use, concomitant therapy with loop diuretics, angiotensin-converting enzyme inhibitors or non-steroidal anti-inflammatory drugs, and renal function were not. By stepwise logistic regression analysis, patient age, body weight and serum potassium were the only independent predictive factors. Each 10-year increment of age was associated with a two-fold increase in risk (hazards ratio 2.14, 95%CI 1.59-2.88). For a 5 kg increment in mass, there was a 27% decrease in odds ratio (odds ratio 0.77, 95%CI 0.68-0.87). One SD increase in serum potassium (0.84 mmol/l) was associated with a 63% decrease in risk (odds ratio 0.37, 95%CI 0.27-0.50; p < 0.0001).

DISCUSSION

Hyponatraemia is a common problem after thiazide therapy. Extra caution and close monitoring are warranted when prescribing thiazides for elderly patients with low body mass.

Hyponatraemia and hypokalaemia due to indapamide

OBJECTIVES

To review Australian adverse drug reaction reports describing hyponatraemia and hypokalaemia attributed to indapamide and compare the characteristics of the patients with those in Australian reports implicating two other diuretic products (hydrochlorothiazide and amiloride hydrochloride; chlorothiazide).

DESIGN

Descriptive analysis using reports from the database of the Adverse Drug Reactions Advisory Committee (ADRAC).

MAIN OUTCOME MEASURES

Numbers of reports of hyponatraemia and hypokalaemia; proportion of such reports in total reports of adverse reactions to each drug; severity of electrolyte disturbances.

RESULTS

Between August 1984 and September 2000, 84 Australian reports of hyponatraemia and 87 reports of hypokalaemia, in which indapamide was the sole suspected drug, were submitted to ADRAC. Most reports involved an indapamide dose of 2.5 mg daily. There was a significantly greater proportion of reports of hyponatraemia with indapamide and with the hydrochlorothiazide and amiloride combination than with chlorothiazide; hypokalaemia was significantly more common for indapamide than for the other two drugs. Of the 87 reports of hypokalaemia with indapamide, 35 patients also had hyponatraemia. For all three drugs, at least 80% of reports of hyponatraemia were in people aged 65 or over, and electrolyte disturbance was most commonly reported in elderly women.

CONCLUSIONS

Hyponatraemia and hypokalaemia have been described in 20.9% and 21.7%, respectively, of reports to ADRAC in which indapamide was the sole suspected drug. The electrolyte disturbances can be severe.

Utility and limitations of biochemical parameters in the evaluation of hyponatremia in the elderly

We evaluated in 110 consecutive elderly hyponatremic patients the value of traditional clinical and biochemical data and the place of a test infusion of 2 liters isotonic saline over 24 hours, in establishing the etiology of the hyponatremia. The causes of hyponatremia were as follows: 31% SIADH patients, 23% patients with hyponatremia due to diuretics, 18% potomania patients, 15% salt depleted patients, 5% salt depleted SIADH patients, 5% patients with a salt loosing syndrome and 3% patients with hyponatremia of unknown origin. Several salt depleted (SD) and SIADH patients could be confounded. Usually, adults with SIADH show plasma uric acid values <4 mg/dL. In our elderly population, 41% of SD patients presented plasma uric acid <4 mg/dL, while 27% of SIADH patients showed plasma uric acid >4 mg/dL. Eighty-two percent of SD patients appeared to have plasma urea levels >30 mg/dL, but this was also the case in 21% of SIADH patients. Twenty-nine of the SD patients presented a urinary sodium >30 mEq/L, but all had fractional sodium excretion (FENa) lower than 0.5%. However, in SIADH, 42% of the patients presented also FENa <0.5%. Fractional excretion of urea (FE urea) below 50% was encountered in 82% of SD patients and FE urea above 50% in only 52% of the SIADH patients. Plasma renin and aldosterone values were poorly discriminative. A test infusion with 2 liters isotonic saline over 24 hours allowed a correct classification of all the patients. In about 2/3 of the population, administration of isotonic saline could be considered as useful (SD, most diuretic patients, potomania patients, salt loosing syndrome patients and some SD SIADH patients). A plasma sodium (PNa) increase of at least 5 mEq/L 24 hours after saline infusion has been suggested as highly suggestive of SD. Nevertheless, 29% of our SD patients did not increase their PNa level by 5 mEq/L or more, while 30% of our SIADH patients did. PNa improved after 2 liters isotonic saline over 24 hours in 90 patients (85%) as opposed to 12 others (9 SIADH and 3 diuretic patients), decreasing their plasma sodium. The isotonic saline infusion test, only allows a reliable classification of hyponatremia, as far as both PNa and sodium excretion were taken into account. In the SIADH group, 6 patients (5%) presented initially manifest solute depletion and retained the 2 liters isotonic saline before developping inappropriate natriuresis. Six patients showed a transient salt loosing syndrome with high fractional potassium excretion (FEK) and high calciuria, which differentiates them from thiazide patients presenting also high FEK, but low calciuria. These patients were also polyuric at admission. The saline infusion was well tolerated in all but 2 patients, developing mild pulmonary congestion at the end of the test infusion.

Drug-induced syndrome of inappropriate antidiuretic hormone secretion. Causes, diagnosis and management

Hyponatraemia is common among the elderly, and may be caused by physiological changes, disease processes or drugs. About half of elderly patients with hyponatraemia have features typical of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). It is important to establish whether drugs are the cause, as this is easily remediable. The clinical manifestations of SIADH are predominantly attributable to hyponatraemia and serum hypo-osmolality. The severity of the signs and symptoms depends on the degree of hyponatraemia and the rapidity with which the syndrome develops. Although a growing number of drugs have been reported to produce SIADH, most published reports concern vasopressin and its analogues, thiazide and thiazide-like diuretics, chlorpropamide, carbamazepine, antipsychotics, antidepressants and nonsteroidal anti-inflammatory drugs. Old age is a risk factor for SIADH following the use of many of these drugs. The use of these drugs in combination, excessive fluid intake and other underlying conditions that limit free water excretion increase the risk. Drug-induced SIADH usually resolves following cessation of the offending agent(s). Additional measures are required in patients with symptomatic hyponatraemia, including fluid restriction and intravenous sodium chloride and/or furosemide (frusemide) therapy. Careful monitoring is essential, with particular attention paid to the rate and extent of correction of the hyponatraemia.

Indapamide-induced severe hyponatremia and hypokalemia

OBJECTIVE

To describe 2 patients with severe indapamide-induced hyponatremia and hypokalemia and to discuss the incidence and mechanisms of diuretic-induced hyponatremia and hypokalemia.

CASE SUMMARY

Two women aged 60 and 62 years presented with severe hyponatremia (plasma sodium concentrations of 103-104 mmol/L) and hypokalemia (plasma potassium concentrations of 1.6-2.2 mmol/L) 5-6 weeks after they received indapamide 2.5 mg/d therapy for arterial hypertension. Central nervous system symptoms of hyponatremia were observed in both patients. One patient experienced severe postural hypotension, a plasma potassium concentration of 1.6 mmol/L, and electrocardiographic abnormalities consistent with hypokalemia. Hyponatremia was initially mistaken in this patient for the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Both patients recovered completely after withdrawal of indapamide therapy and correction of the hyponatremia and hypokalemia.

DISCUSSION

Previous studies of administration of indapamide 2.5 mg/d for 10-24 months in hypertensive patients showed a low incidence (0.6-1.2%) of hypokalemia severe enough to require withdrawal of drug therapy. Serum sodium concentrations were unaltered in these studies. All case reports, except 1, of indapamide-induced electrolyte disturbances described only hypokalemia.

CONCLUSIONS

Indapamide can cause both severe hypokalemia and hyponatremia. The predominant clinical features can be a result of severe hyponatremia. The latter can have diverse clinical presentations and may be mistaken for SIADH. As with other diuretics, plasma sodium and potassium concentrations must be monitored during indapamide therapy, especially in patients at risk for hyponatremia and hypokalemia.

A study of plasma sodium levels in elderly people taking amiloride or triamterene in combination with hydrochlorothiazide

This study was performed to compare the effect of one month's treatment with hydrochlorothiazide (25 mg) in combination with either amiloride (2.5 mg) or triamterene (50 mg) on plasma sodium levels in elderly people in institutional care. Fifty residents of NHS nursing or social service residential care established on diuretics for congestive cardiac failure and aged 64 years or over were recruited. Forty-one patients were included in the final data analysis. Patients on hydrochlorothiazide/amiloride had a significantly lower plasma sodium (137 vs 139 mmol/l, 95% confidence interval for difference between medians 0-2 mmol/l) than those on hydrochlorthiazide/triamterene (P = 0.01). In equivalent potassium-retaining doses, amiloride is associated with significantly lower plasma sodium levels than triamterene, when given in combination with hydrochlorothiazide in elderly patients with congestive cardiac failure. This finding adds weight to uncontrolled observations implicating thiazide/amiloride diuretic combinations in causing serious hyponatraemia. This danger, although uncommon, should perhaps influence prescribing habits in an at-risk population.

Post-marketing surveillance of drugs. The spontaneous reporting scheme: role of the Adverse Drug Reactions Advisory Committee

Post-marketing surveillance of drugs in Australia operates predominantly through the spontaneous reporting of suspected adverse drug reactions (ADRs). Approximately 50% of reports are submitted by hospitals and the rest by individual doctors, pharmacists and dentists. Some 4500 reports ("blue cards") are now reviewed annually by the Adverse Drug Reactions Advisory Committee (ADRAC) and its Secretariat. The register of ADRs has now accumulated more than 65,000 reports. Collations and analyses of data derived from the review process are published to increase awareness by health professionals of drug associated morbidity. Continued educational efforts by professional bodies and regulatory agencies will play a key role in rationalising drug use and reducing drug induced disease.