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Stability of spironolactone in an extemporaneously prepared suspension at two temperatures.

OBJECTIVE: To determine the stability of spironolactone in an extemporaneously prepared suspension at 22 and 4 degrees C over a three-month storage period. DESIGN: Spironolactone suspension (1 mg/mL) was prepared in syrup NF, carboxymethylcellulose, and purified water USP. The suspension was stored in ten amber glass prescription bottles; five were stored at 22 degrees C and five at 4 degrees C. Samples were drawn from each bottle and analyzed in duplicate (n = 10) on days 0, 7, 14, 28, 42, 56, 70, and 91. Spironolactone concentrations were measured by a reproducible and stability-indicating HPLC method. Inspection of visual and pH changes also was performed on each study day. RESULTS: The mean concentration of spironolactone was always higher than 98 percent of its initial concentration. The pH and appearance of the suspension did not change substantially. CONCLUSIONS: Spironolactone was stable in a suspension containing syrup, carboxymethylcellulose, and purified water for three months during storage in amber glass bottles at both 22 and 4 degrees C.

Carboxymethylcellulose Sodium↗

Spironolactone, but not flutamide, administration prevents bone loss in hyperandrogenic women treated with gonadotropin-releasing hormone agonist.

GnRH agonists (GnRHa) have recently been proposed for the treatment of hirsutism in women with the polycystic ovary syndrome (PCOS). As most of these subjects have increased androgen secretion from both ovaries and adrenal glands, the association of GnRHa with antiandrogen drugs might enhance the clinical response to treatment. On the other hand, this association might also potentiate the adverse effects of GnRHa on bone metabolism, generating a potentially harmful situation at the skeletal level. In this study we investigated in 41 PCOS patients the skeletal effects of a 6-month course of GnRHa (tryptorelin, 3.75 mg, i.m., monthly), either alone (n = 12) or associated with the antiandrogen drugs spironolactone (100 mg, orally, once daily; n = 14) or flutamide (250 mg, once daily; n = 15). In all subjects bone mineral density was measured before and after treatment by dual energy x-ray absorptiometry at the lumbar spine (L2-L4) and at the femoral neck and Ward's triangle. In addition, at baseline and after 6 months of therapy, bone metabolism markers (serum and urinary calcium, serum phosphorus and alkaline phosphatase, plasma osteocalcin, and urinary hydroxyproline) and endocrine parameters (serum gonadotropins, estradiol, and free testosterone) were assayed. Women given either GnRHa alone or associated with spironolactone or flutamide were similar for age and body mass index. At baseline, the 3 groups of PCOS women were also similar for endocrine and bone parameters. After 6 months, all treatments determined similar striking suppressions of serum gonadotropins and sex steroids. Concurrently, bone mineral density was significantly reduced at all examined sites in subjects receiving either GnRHa alone or GnRHa plus flutamide. Conversely, women given GnRHa plus spironolactone did not show any change in skeletal mass from baseline values (P < 0.05-0.01 among groups). Biochemical parameters of bone metabolism were consistent with densitometric assessments. In conclusion, after a 6-month course of therapy, bone mineral density is reduced in PCOS women given either GnRHa alone or GnRHa plus flutamide, but not in those receiving GnRHa plus spironolactone. The mechanisms of the bone-sparing effect of spironolactone remain to be determined. Nevertheless, this drug could represent a useful tool to prevent skeletal loss in women given GnRHa as well as in other hypoestrogenic conditions, in particular when estrogens are not recommended.

Adult↗

Administration time-dependent change in the effect of spironolactone in rats.

The present study was undertaken to examine whether the natriuretic effect of spironolactone, a competitive antagonist of mineralocorticoid, varies with its time of administration. Wistar rat maintained under the condition of light from 7 hr to 19 hr were divided into two groups. The first group had a bilateral adrenalectomy and received a 50-mg deoxycorticosterone acetate (DOCA) tablet intraperitoneally (DOCA group). The second group had a sham operation (control group). Spironolactone (50 mg/kg) was given orally at 12 hr or 24 hr, and the 8-hr urine was collected. At the end of the experiment, the blood sample for measurement of aldosterone was obtained at 12 hr and 24 hr in the control group. The natriuretic effect of spironolactone in the 24 hr-trial was significantly greater than that of the 12 hr-trial in the control group. However, such a time-dependent difference was diminished and did not reach statistical significance in the DOCA group. The plasma aldosterone concentration at 24 hr was significantly higher than that at 12 hr in the control group. These results suggest that the natriuretic effect of spironolactone varies with its time of administration. Daily variation in mineralocorticoid activity might be involved in this chronopharmacological phenomenon of spironolactone.

Administration, Oral↗

Effects of spironolactone and angiotensin-converting enzyme inhibitor on left ventricular hypertrophy in patients with essential hypertension.

There is increasing evidence for important cardiovascular effects of aldosterone via classical mineralocorticoid receptors in the heart. Administration of aldosterone with excess salt produces both cardiac hypertrophy and interstitial cardiac fibrosis in rats, and concomitant administration of potassium canrenoate at a dose that only modestly lowers blood pressure completely blocks the cardiac effects of aldosterone. In the present study, we examined the effect on left ventricular hypertrophy of adding a low dose of the mineralocorticoid receptor antagonist spironolactone (25 mg/d) to an angiotensin-converting enzyme inhibitor (enalapril maleate) in patients with essential hypertension. Eighteen untreated patients with moderate to severe essential hypertension based on the WHO/ISH guidelines participated in this study. Subjects were treated with either an angiotensin-converting enzyme inhibitor alone (group I: 10 patients, 4 men and 6 women, mean age 56 +/- 18 yr) or an angiotensin-converting enzyme inhibitor plus spironolactone (group II: 8 patients, 3 men and 5 women, mean age 59 +/- 14 yr) for 9 mo. Left ventricular mass index, various echocardiographic variables, mean blood pressure, plasma renin activity, and plasma aldosterone concentration before treatment were similar in the two groups. Blood pressure of both groups decreased significantly and similarly after antihypertensive treatment (group I, 136 +/- 9/82 +/- 9 mmHg; group II, 133 +/- 9/85 +/- 10 mmHg). Left ventricular mass index also decreased significantly in both groups (group I, -10.2 +/- 7.1%; group II, -18.1 +/- 6.9%). The extent of reduction was significantly greater in the spironolactone group (group II) (p < 0.05 vs. group I). In group II patients, spironolactone did not cause any side effects during the observation period. We conclude that spironolactone may have beneficial effects on left ventricular hypertrophy in patients with essential hypertension who are receiving an angiotensin-converting enzyme inhibitor.

Aldosterone↗

Relative long-term effects of spironolactone in conjunction with an angiotensin-converting enzyme inhibitor on left ventricular mass and diastolic function in patients with essential hypertension.

It has been reported that treatment with an angiotensin-converting enzyme (ACE) inhibitor is not adequate to suppress aldosterone, and we previously demonstrated that adding spironolactone to an ACE inhibitor may have beneficial effects on left ventricular hypertrophy (LVH) in selected patients with essential hypertension (EH). We have extended our previous short-term study, and addressed the relative long-term clinical effects of spironolactone and an ACE inhibitor in patients with EH who have LVH. Twenty patients with EH and concomitant LVH participated in this study. Subjects were treated with either an ACE inhibitor alone (group 1: 10 patients) or an ACE inhibitor plus spironolactone at the dose of 25 mg (group 2: 10 patients) for 60 weeks. The baseline clinical and echocardiographic characteristics of the two groups were similar. Final values of blood pressure were also similar between the two groups. The LV mass index (LVMI) decreased significantly in both groups, but the extent of reduction was significantly greater in group 2 at 60 weeks. The early peak to atrial peak filling velosities ratio (E/A ratio) was significantly increased to a similar extent in both groups. Serum procollagen type III amino-terminal peptide (PIIINP) was significantly decreased in group 2, but not in group 1. In group 2, there was a statistically significant correlation between the changes in LVMI and PIIINP. In conclusion, adding spironolactone to therapy with an ACE inhibitor for 60 weeks may have beneficial effects in patients with EH and concomitant LVH. Our study strongly suggests the possibility that attenuation of the effects of cardiac aldosterone in patients with EH by treatment with spironolactone and an ACE inhibitor may become a new goal for the prevention and regression of cardiac hypertrophy.

Adult↗

Cardioprotective mechanisms of spironolactone associated with the angiotensin-converting enzyme/epidermal growth factor receptor/extracellular signal-regulated kinases, NAD(P)H oxidase/lectin-like oxidized low-density lipoprotein receptor-1, and Rho-kinase pathways in aldosterone/salt-induced hypertensive rats.

Studies were performed to test the hypothesis that the angiotensin-converting enzyme (ACE)/epidermal growth factor receptor (EGFR)/extracellular signal-regulated kinases (ERK) pathway, nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase/lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) pathway, and Rho-kinase pathway contribute to the pathogenesis of aldosterone/salt-induced hypertensive rats. Wistar rats were given 1% NaCl to drink and treated with one of the following combinations for 6 weeks: vehicle; aldosterone (0.75 microg/h); aldosterone plus a mineralocorticoid receptor antagonist, spironolactone (20 mg/kg/day); aldosterone plus an ACE inhibitor, imidapril (1 mg/kg/day); aldosterone plus an NAD(P)H oxidase inhibitor, apocynin (0.5 mmol/l); and aldosterone plus an Rho-kinase inhibitor, Y-27632 (3 mg/kg/day). Upregulated expression of ACE and EGFR and p44/p42ERK phosphorylation were suppressed by spironolactone or imidapril. Upregulated NAD(P)H oxidase subunits and LOX-1 expression were inhibited by spironolactone or apocynin. Increased expression of RhoA and Rho-kinase and myosin light chain phosphorylation were decreased by spironolactone or Y-27632. Moreover, these drugs effectively inhibited the vascular lesion formation, as measured by the medial thickness and level of perivascular fibrosis, and suppressed the expression of transforming growth factor-beta1, type I and III collagen, and monocyte chemoattractant protein-1 mRNA. Spironolactone may be useful as a cardioprotective agent to prevent cardiovascular remodeling via the ACE/EGFR/ERK, NAD(P)H oxidase/LOX-1, and Rho-kinase pathways.

Aldosterone↗

Clinical experience with spironolactone in pediatrics.

BACKGROUND: In 2003, the Food and Drug Administration placed spironolactone on its list of drugs needing pediatric studies. OBJECTIVE: To describe the use of spironolactone in a large group of children and evaluate its safety, focusing on its effects on potassium. METHODS: A prospective observational study was conducted. Patient demographic information was collected, as well as dosing regimens, use of other medications, and potassium concentrations. Patients were grouped by diagnosis. Comparisons were made with unpaired t-tests. RESULTS: One hundred consecutive patients were evaluated. The average age was 20.8 months and weight was 9.5 kg. Sixty-two patients had heart disease (HD), 29 had chronic lung disease (CLD), and 9 had other conditions. The initial dose was 1.8 +/- 0.7 mg/kg/day. Patients with CLD received a higher dose than those with HD (2 +/- 0.8 vs 1.7 +/- 0.5 mg/kg/day; p = 0.04). Sixty-six patients received furosemide and 37 received thiazides (12 received both). The average potassium concentration after initiation was 4.3 +/- 0.8 mEq/L, with higher values in patients with CLD versus HD (4.7 +/- 0.7 vs 4.2 +/- 0.7 mEq/L; p = 0.007). Twenty-six patients required potassium supplementation, including 16 with CLD and 8 with HD; no other adverse effects were noted. Average length of treatment was 16 days, with a length of stay of 38 days. Of the 92 patients surviving to discharge, 66 continued on spironolactone. CONCLUSIONS: This sample demonstrates that spironolactone is a common component of diuretic regimens in pediatric patients. The only adverse effects were alterations in potassium. While hyperkalemia was more common initially, hypokalemia was more frequent with long-term use. Potassium concentrations should be carefully monitored, particularly in children receiving multiple diuretics. Additional research is needed to define the pharmacokinetics and optimal dosing interval of spironolactone, as well as determine its long-term effects on potassium.

Chronic Disease↗

Hypokalemic and ECG sequelae of combined beta-agonist/diuretic therapy. Protection by conventional doses of spironolactone but not triamterene.

Salbutamol (Albuterol) and diuretics are commonly prescribed together in patients with airflow obstruction and are associated with electrocardiographic effects. We have now investigated whether the use of potassium-sparing drugs might prevent the ECG sequelae of such combined therapy. Ten healthy subjects received seven days of randomized treatments with: placebo, bendrofluazide (5 mg), bendrofluazide plus triamterene 50 mg (conventional dose), or triamterene 200 mg (high dose), and bendrofluazide plus spironolactone (100 mg). Potassium and ECG responses to inhaled salbutamol, 2 mg, were measured after each treatment period. The T-wave flattening in response to bendrofluazide and salbutamol (0.24[CI, 0.19 to 0.29]mV) was attenuated by the addition of triamterene, 200 mg (0.33[CI, 0.28 to 0.37]mV; p less than 0.05) and spironolactone 100 mg (0.42[CI, 0.37 to 0.47]mV; p less than 0.01), but not by triamterene 50 mg (0.25[CI, 0.20 to 0.30]mV). Spironolactone and high dose triamterene also diminished the frequency of U waves and ST depression. The ECG effects mirrored hypokalemic responses which were also blunted by high dose (p less than 0.01) but not low dose triamterene, as well as by spironolactone (p less than 0.001). Thus, the use of high dose triamterene and spironolactone protected against the hypokalemic and ECG sequelae of combined beta-agonist/diuretic therapy, whereas a conventional dose of triamterene had no effect. These findings may be important in the prevention of a potentially dangerous interaction in susceptible patients taking this combination of drugs.

Adult↗

Aldosterone response to adrenocorticotrophin and furosemide in primary aldosteronism after prolonged spironolactone treatment.

We evaluated the effects of prolonged spironolactone treatment on aldosterone secretion in patients with primary aldosteronism. The patients were hospitalized and underwent a furosemide test with or without dexamethasone, as well as an adrenocorticotrophin (ACTH) test. In untreated patients, neither plasma renin activity (PRA) nor plasma aldosterone showed a response in the furosemide test. In patients receiving spironolactone, furosemide increased significantly both the PRA and the plasma aldosterone concentration (from 2.6 +/- 0.8 to 7.0 +/- 2.0 micrograms.l-1.h-1 (p < 0.05) and from 345.6 +/- 55.8 to 492.7 +/- 76.8 ng/l (p < 0.05), mean +/- SEM, respectively). Dexamethasone administration had no effect on the results of the furosemide test (p > 0.1). However, dexamethasone tended to decrease the basal plasma aldosterone concentration in the untreated patients, but not in the patients receiving spironolactone. In the ACTH test, the plasma aldosterone concentration increased significantly in the untreated patients (from 549.0 +/- 69.8 to 1169.3 +/- 165.5 ng/l, p < 0.01), but there was no significant aldosterone response in the spironolactone-treated patients (from 885.5 +/- 204.9 to 1260.3 +/- 289.2 ng/l, p > 0.1). We conclude that aldosterone secretion is mainly dependent on ACTH in the untreated patients with primary aldosteronism and is more strongly regulated by the renin-angiotensin system during spironolactone treatment.

Adrenocorticotropic Hormone↗

Racial differences in patients' potassium concentrations during spironolactone therapy for heart failure.

STUDY OBJECTIVE: To determine whether the effects of spironolactone on potassium homeostasis vary by race by comparing serum potassium concentrations and potassium supplement use in African-American and Caucasian patients receiving spironolactone for heart failure. DESIGN: Retrospective medical record review. SETTING: Two heart failure centers. PATIENTS: Fifty African-American and 67 Caucasian patients with heart failure who were receiving a stable dosage of spironolactone in addition to standard heart failure therapy with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker. MEASUREMENTS AND MAIN RESULTS: Medical records of eligible patients were reviewed by pharmacists and physicians who specialize in heart failure management. No significant differences were observed in diuretic therapy or renal function between racial groups; however, African-Americans were receiving higher doses of ACE inhibitors. African-Americans had lower serum potassium concentrations (4.2 +/- 0.4 vs 4.5 +/- 0.5 mEq/L, p<0.01) and a higher prevalence of potassium supplementation (48% vs 15%, p<0.01). In a subset of patients, spironolactone therapy was associated with a 2-fold greater increase in serum potassium concentration and a 3-fold greater reduction in potassium supplement use among Caucasians than African-Americans. CONCLUSION: Our findings suggest that a large percentage of patients with heart failure, particularly African-Americans, still require potassium supplementation despite treatment with spironolactone and standard vasodilator therapy.

Adrenergic beta-Antagonists↗

Determinants of spironolactone binding specificity in the mineralocorticoid receptor.

Spironolactone is a mineralocorticoid receptor (MR) antagonist in clinical use. The compound has a very low affinity for the glucocorticoid receptor (GR). Determinants of binding specificity of spironolactone to the MR were investigated using chimeras created between the ligand-binding domains (LBDs) of the MR and the GR. These chimeras had previously been used to investigate aldosterone binding specificity to the MR. Spironolactone was able to compete strongly for [(3)H]-aldosterone and [(3)H]-dexamethasone binding to a chimera containing amino acids 804-874 of the MR, and weakly for [(3)H]-dexamethasone binding to a chimera containing amino acids 672-803 of the MR. Amino acids 804-874 were also critical for aldosterone binding specificity. Models of the MR LBD bound to aldosterone and spironolactone were created based on the crystal structure of the progesterone receptor LBD. The ligand-binding pocket of the MR LBD model consisted of 23 amino acids and was predominantly hydrophobic in nature. Analysis of this model in light of the experimental data suggested that spironolactone binding specificity is not governed by amino acids in the ligand-binding pocket.

Aldosterone↗

Effect of spironolactone on androgen-dependent proteins in the ventral prostate of the rat.

The effect of spironolactone on five androgen-dependent proteins in the ventral prostate of the rat was investigated by two-dimensional gel electrophoresis. Spironolactone was given to intact male, castrated and androgen-stimulated castrated rats. It has been shown that spironolactone had no influence on the synthesis or accumulation of the androgen-dependent proteins in intact animals. However, spironolactone suppressed the restoration of the major androgen-dependent protein of low molecular weight in castrated rats given testosterone. The mechanism by which spironolactone exerts its anti-androgenic activity was shown to be unrelated to its capacity to inhibit the synthesis or accumulation of the five androgen-dependent proteins studied in this investigation.

Animals↗

Comparison of the efficiency of anti-androgenic regimens consisting of spironolactone, Diane 35, and cyproterone acetate in hirsutism.

The aim of the present study was to evaluate the effects of three different anti-androgenic drug-therapy regimens, Diane 35 (cyproterone acetate (CPA) [2 mg] and ethinyl estradiol [35 microg]) plus CPA, Diane 35 plus spironolactone, and spironolactone alone, in patients with hirsutism. In this prospective, randomized clinical study, 79 subjects with idiopathic hirsutismus were studied. The patients were divided into 3 groups. Group I patients (n=32) were treated with Diane 35 plus CPA, group II patients (n=25) with Diane 35 plus spironolactone [100 mg], and group III patients (n=22) with spironolactone [100 mg] alone. Serum FSH, LH, testosterone (T), and DHEAS levels were analyzed before and after treatment at 6 and 12 months. Hirsutism scores were graded according to the Ferriman-Gallwey scoring system, and side effects were monitored. All treatment regimens were found to be efficient and well-tolerated, and none of the patients stopped therapy due to any adverse event. However, in hormone screening, only patients on the Diane 35 plus CPA regimen revealed a decrease in serum T levels after therapy. As such, treatment of each hirsute patient should be planned individually, but with regard to both cost-efficiency and potential side effects, we recommend spironolactone alone in the treatment of hirsutismus.

Adolescent↗

Beneficial effects of adding spironolactone to recommended antihypertensive treatment in diabetic nephropathy: a randomized, double-masked, cross-over study.

OBJECTIVE: The objective of this study was to evaluate the safety and short-term effect of adding spironolactone to conventional antihypertensive treatment including diuretics and maximally recommended doses of an ACE inhibitor or an angiotensin II receptor blocker (ARB) on albuminuria and blood pressure in type 2 diabetic patients with nephropathy. RESEARCH DESIGN AND METHODS: Twenty-one type 2 diabetic patients with nephropathy were enrolled in a randomized, double-masked, cross-over study. Patients were treated in random order with spironolactone 25 mg once daily and matched placebo for 8 weeks, respectively, in addition to ongoing antihypertensive treatment including diuretics and maximally recommended doses of an ACE inhibitor and/or an ARB. At the end of each treatment period, albuminuria, 24-h ambulatory blood pressure (ABP), and glomerular filtration rate (GFR) were determined. RESULTS: During the addition of placebo, values were as follows: albuminuria (geometric mean [range]) 1,566 [655-7,762] mg/24 h, ABP (mean +/- SE) 138 +/- 3/71 +/- 1 mmHg, and GFR (mean +/- SE) 74 +/- 6 ml/min per 1.73 m2. During the addition of spironolactone, albuminuria was reduced by 33% (95% CI 25-41) (P < 0.001), fractional clearance of albumin by 40% (24-53) (P < 0.001), and 24-h ABP by 6 mmHg (2-10) for systolic and 4 mmHg (2-6) for diastolic (P < 0.001 for both). The change in albuminuria did not correlate with the change in systolic 24-h ABP (r = 0.19, P = 0.42) or diastolic 24-h ABP (r = 0.01, P = 0.96). Spironolactone treatment induced an insignificant reversible reduction in GFR of 3 ml/min per 1.73 m2 (-0.3 to 6) (P = 0.08). One patient was excluded from the study due to hyperkalemia. Otherwise treatment was well tolerated. CONCLUSIONS: Our study suggests that spironolactone safely adds to the reno- and cardiovascular protective benefits of treatment with maximally recommended doses of ACE inhibitor and ARB by reducing albuminuria and blood pressure in type 2 diabetic patients with nephropathy.

Antihypertensive Agents↗

Factors affecting the frequency of occurrence of spironolactone bodies in aldosteronomas and non-tumorous cortex.

Histological sections taken from aldosterone-producing-adenomas and from non-tumorous adrenal cortex of 18 patients treated for primary aldosteronism by unilateral adrenalectomy were examined for spironolactone inclusion bodies. Typical inclusions were found in 10 of the 13 patients who received spironolactone up to within 24 h of surgery. They were present in the tumours of 7 patients, and their frequency correlated positively with the percentage of glomerulosa type cells in the tumours. In tumours containing 50% or more glomerulosa-type cells, their frequency correlated negatively with duration of treatment. They were present in the non-tumorous cortex of 4 of these 7 patients, and in the cortex of 3 others whose tumours did not contain them. In the cortex, they were found only in glomerulosa cells, and their presence appeared unrelated to dosage or duration of treatment. No spironolactone inclusion bodies were seen in either the tumour of the non-tumorous cortex of 3 patients who had discontinued spironolactone 19 to 97 d before surgery, or of 2 patients who had never received spironolactone.

Adenoma↗

Pathophysiology of spironolactone-induced gynecomastia.

Peripheral blood levels of testosterone, estradiol, luteinizing hormone, and follicle-stimulating hormone and the metabolic clearance rates of testosterone and estradiol, as well as the peripheral conversion of testosterone into estradiol, were measured in 16 patients with hypertension. Six of these patients were treated with spironolactone and developed gynecomastia. The other 10 patients served as control subjects. The blood testosterone level in the spironolactone-treated group (2.7 +/- 0.5 ng/ml) was significantly less (P less than 0.02) than in the control group (4.4 +/- 0.4 ng/ml). On the other hand, blood estradiol levels in the spironolactone group (30 +/- 4 pg/ml) were significantly greater (P less than 0.01) than in the control group (13 +/- 2 pg/ml). These changes were primarily due to significant increases in the metabolic clearance rate of testosterone (P less than 0.02) and in the rate of peripheral conversion of testosterone into estradiol (P less than 0.001) in the spironolactone-treated group. Thus, spironolactone does alter the peripheral metabolism of testosterone resulting in changes in the ratio of testosterone to estradiol, which could contribute to the production of gynecomastia.

Adult↗

Spironolactone-induced hyperchloremic acidosis in cirrhosis.

Six patients with alcoholic cirrhosis developed a reversible metabolic acidosis during treatment with the aldosterone antagonist spironolactone. Mean serum bicarbonate concentration decreased significantly with spironolactone therapy (100 to 200 mg/day) from 18.2 +/- 4.5 to 10.9 +/- 3.2 meq/litre (P less than 0.001). Upon withdrawal of spironolactone, serum bicarbonate concentration increased from 10.9 +/- 3.2 to 18.1 +/- 3.5 meq/litre (P less than 0.001). During the development of this hyperchloremic metabolic acidosis, serum potassium concentration rose from 3.7 +/- 0.5 to 5.0 +/- 0.8 meq/litre (P less than 0.005); this reversed after cessation of spironolactone therapy. These effects of spironolactone treatment were not associated with significant alterations in serum creatinine or sodium concentration. Thus, even though an aldosterone antagonist in the treatment of sodium and water retention in cirrhotic patients may prevent hypokalemia and rapid diuresis, it may also induce or worsen another complication: hyperchloremic metabolic acidosis.

Acidosis↗

Digoxin assays: frequent, substantial, and potentially dangerous interference by spironolactone, canrenone, and other steroids.

BACKGROUND: A case of digoxin toxicity resulted from falsely low values with the MEIA II assay for digoxin (AxSYM; Abbott). The low results were caused by negative interference from canrenone and spironolactone, the latter of which has recently been advocated for the treatment of severe heart failure. Analytical interference from spironolactone has been reported, but little information is available for this effect with newer digoxin assays. METHODS: We examined nine assays (AxSYM, IMx, TDx, Emit, Dimension, aca, TinaQuant, Elecsys, and Vitros for interference by spironolactone, canrenone, and three metabolites. Additionally, all routine digoxin measurements (AxSYM) over a period of 16.5 months (n = 3089) were monitored for interference. RESULTS: Suppression of the expected values by canrenone (3125 microg/L) was observed for the AxSYM (42% of expected value), IMx (51%), and Dimension (78%) assays. A positive bias was observed for the aca (0.7 microg/L), the TDx (0.62 microg/L), and the Elecsys (>0.58 microg/L). Twenty-five of 669 routinely monitored patients had falsely low results. Nineteen of these had potentially toxic concentrations of digoxin (Emit; >2.0 microg/L), although the AxSYM assay indicated therapeutic or less severe toxic concentrations (Delta(max) = 7.1 microg/L). Except for two unresolved cases, this was attributable to spironolactone, canrenone, hydrocortisone, or prednisolone. Standard doses of spironolactone (up to 50 mg/day) in patients with heart failure displayed inhibition <11%. CONCLUSIONS: The frequency and magnitude of the false-negative results particularly compromise the use of both microparticle enzyme immunoassays. Not only may toxic concentrations remain unidentified, but intoxication could occur should dosage be increased because of falsely low results. With 11 million digoxin tests/year ordered in the US, conceivably many patients could be adversely affected.

Anti-Arrhythmia Agents↗