Effectiveness of chlorthalidone/amiloride versus losartan in patients with stage I hypertension and diabetes mellitus: results from the PREVER-treatment randomized controlled trial

AIMS

To compare the blood pressure (BP)-lowering efficacy of a chlorthalidone/amiloride combination pill with losartan, during initial management of JNC 7 Stage I hypertension in patients with type 2 diabetes mellitus.

METHODS

In an a priori subgroup analysis of a randomized, double-blind, controlled trial, volunteers aged 30-70 years, with stage I hypertension and diabetes mellitus, were randomized to 12.5/2.5 mg of chlorthalidone/amiloride (N = 47) or 50 mg of losartan (N = 50), and followed for 18 months in 21 clinical centers. If BP remained uncontrolled after three months, study medication dose was doubled, and if uncontrolled after six months, amlodipine (5 and 10 mg) and propranolol (40 and 80 mg BID) were added as open label drugs in a progressive fashion.

RESULTS

Systolic BP decreased to a greater extent in participants allocated to diuretics compared to losartan (P < 0.001). After 18 months of follow-up, systolic BP was 128.4 ± 10.3 mmHg in the diuretic group versus 133.5 ± 8.0 in the losartan group (P < 0.01). In the diuretic group, 36 out of 43 participants (83.7%) had a JNC 7 normal BP, compared to 31/47 (66%) in the losartan group (P = 0.089). Serum cholesterol was higher in the diuretic arm at the end of the trial. Other biochemical parameters and reports of adverse events did not differ by treatment.

CONCLUSIONS

Treatment of hypertension based on a combination of chlorthalidone and amiloride is more effective for BP lowering compared to losartan in patients with diabetes mellitus and hypertension.

TRIAL REGISTRATION

Clinical trials registration number: NCT00971165.

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.

Diuretics and Electrolyte Disturbances in 1000 Consecutive Geriatric Admissions

Old people are commonly receiving diuretics on admission to hospital. Diuretics are recognized as a risk factor for electrolyte disturbances; controversy exists about the relative risks of different combinations (in particular, co-amilozide [Moduretic]). We recorded the drug history and serum electrolytes in 1000 consecutive admissions to a geriatric hospital, and examined the relative prescribing rates of various diuretics in the community.

Full results were obtained in 929 patients. A history of diuretic prescription was present in 353 (38%) of the patients; the mean serum sodium in this group (95% CI 136.0–137.1 mmol/1) was lower than in the 586 not prescribed diuretics (137.1–137.9 mmol/1). The difference was small but statistically significant (95% CI difference=0.3–1.6 mmol/1; P<0.01).

Hyponatraemia (serum sodium < 130 mmol/l) was not significantly commoner in the 41 patients prescribed co-amilozide than in patients prescribed other diuretics. In general patients prescribed potassium-retaining diuretics had a lower serum sodium than the others.

There was a significant positive correlation between the serum potassium and the log [serum urea) (r=0.26, P < 0.001) and a weak negative correlation existed between sodium and potassium (r= −0.14; P < 0.001). There was an association between the prescription of potassium-retaining diuretics and a higher serum potassium; also an association between the prescription of a loop or thiazide diuretic and a lower serum potassium. These interactions were shown by multiple regression analysis to be independent and additive.

Co-amilozide formed a significantly higher proportion of all diuretics prescribed in the community group than in the inpatient group (18% versus 12%; P < 0.05).

Hyponatraemia was mild and mainly associated with potassium-retaining diuretics in our patients. Our study was unable to confirm or refute any specific dangers of co-amilozide compared with other potassium-retaining diuretic combinations.

Comparison of single and combination diuretics on glucose tolerance (PATHWAY-3): protocol for a randomised double-blind trial in patients with essential hypertension

INTRODUCTION

Thiazide diuretics are associated with increased risk of diabetes mellitus. This risk may arise from K(+)-depletion. We hypothesised that a K(+)-sparing diuretic will improve glucose tolerance, and that combination of low-dose thiazide with K(+)-sparing diuretic will improve both blood pressure reduction and glucose tolerance, compared to a high-dose thiazide.

METHODS AND ANALYSIS

This is a parallel-group, randomised, double-blind, multicentre trial, comparing hydrochlorothiazide 25-50 mg, amiloride 10-20 mg and combination of both diuretics at half these doses. A single-blind placebo run-in of 1 month is followed by 24 weeks of blinded active treatment. There is forced dose-doubling after 3 months. The Primary end point is the blood glucose 2 h after oral ingestion of a 75 g glucose drink (OGTT), following overnight fasting. The primary outcome is the difference between 2 h glucose at weeks 0, 12 and 24. Secondary outcomes include the changes in home systolic blood pressure (BP) and glycated haemoglobin and prediction of response by baseline plasma renin. Eligibility criteria are: age 18-79, systolic BP on permitted background treatment ≥ 140 mm Hg and home BP ≥ 130 mm Hg and one component of the metabolic syndrome additional to hypertension. Principal exclusions are diabetes, estimated-glomerular filtration rate <45 mL/min, abnormal plasma K(+), clinic SBP >200 mm Hg or DBP >120 mm Hg (box 2). The sample size calculation indicates that 486 patients will give 80% power at α=0.01 to detect a difference in means of 1 mmol/L (SD=2.2) between 2 h glucose on hydrochlorothiazide and comparators.

ETHICS AND DISSEMINATION

PATHWAY-3 was approved by Cambridge South Ethics Committee, number 09/H035/19. The trial results will be published in a peer-reviewed scientific journal.

TRIAL REGISTRATION NUMBERS

Eudract number 2009-010068-41 and clinical trials registration number: NCT02351973.

Fidelity variants of RNA dependent RNA polymerases uncover an indirect, mutagenic activity of amiloride compounds

In a screen for RNA mutagen resistance, we isolated a high fidelity RNA dependent RNA polymerase (RdRp) variant of Coxsackie virus B3 (CVB3). Curiously, this variant A372V is also resistant to amiloride. We hypothesize that amiloride has a previously undescribed mutagenic activity. Indeed, amiloride compounds increase the mutation frequencies of CVB3 and poliovirus and high fidelity variants of both viruses are more resistant to this effect. We hypothesize that this mutagenic activity is mediated through alterations in intracellular ions such as Mg²⁺ and Mn²⁺, which in turn increase virus mutation frequency by affecting RdRp fidelity. Furthermore, we show that another amiloride-resistant RdRp variant, S299T, is completely resistant to this mutagenic activity and unaffected by changes in ion concentrations. We show that RdRp variants resist the mutagenic activity of amiloride via two different mechanisms: 1) increased fidelity that generates virus populations presenting lower basal mutation frequencies or 2) resisting changes in divalent cation concentrations that affect polymerase fidelity. Our results uncover a new antiviral approach based on mutagenesis.

RNA viruses have extreme mutation frequencies, due in large part to the erroneous nature of the viral RNA dependent RNA polymerases (RdRp) that replicate their genomes. Since RdRp lack proofreading and repair mechanisms, the use of base analogs as RNA mutagens to increase lethal mutations and extinguish the virus population is a promising antiviral strategy. Recently, a screen for resistance to this antiviral treatment identified a higher fidelity RdRp variant of poliovirus, indicating that RdRp fidelity can be modulated by single amino acid substitutions. To extend these observations to other viruses, we performed a similar screen using Coxsackie virus B3 (CVB3). We identified a new high fidelity RdRp variant which was also resistant to amiloride compounds that have no known mutagenic activity. Using wild type and RdRp fidelity variants of poliovirus and CVB3, we show that amiloride compounds do have mutagenic activity and act on RNA virus populations indirectly, by altering intracellular ion concentrations that affect polymerase fidelity. Our results identify a new means of targeting viruses through increases in mutation frequency using non-nucleoside compounds that alter the cellular environment in which the virus replicates.

Amiloride-induced hyponatremia

We present three aged female patients who fulfil the criteria of a syndrome that we call "amiloride hyponatremia". They became hyponatremic during amiloride + hydrochlorothiazide therapy. They needed diuretic therapy and tolerated well hydrochlorothiazide with potassium supplementation as potassium chloride. Patients with hyponatremia during diuretic therapy for cardiovascular diseases can be allocated to three groups: 1) Patients with edema and water retention due to severe impairment of cardiac function and decreased water clearance. They need diuretic therapy and water restriction. 2) Patients with "normal diuretic hyponatremia". Hypokalemia and extracellular volume contraction seem to be associated with this phenomenon, and the therapy involves discontinuing the necessary diuretic treatment. 3) Patients with "amiloride hyponatremia". They need diuretic treatment and tolerated thiazide therapy, but the hyponatremia can be corrected by changing amiloride to potassium supplementation. "Amiloride hyponatremia" is suggested to be due to a direct effect of amiloride + hydrochlorothiazide on the distal nephrons. The combination amiloride + hydrochlorothiazide must be used cautiously in elderly patients and the possibility of hyponatremia should be born in mind cases of vague symptoms and CNS disturbances.

Ventricular dysrhythmias in middle-aged hypertensive men treated either with a diuretic agent or a beta-blocker

The purpose of this study was to identify the frequency of cardiac dysrhythmias in two similar groups of hypertensive middle-aged males (age 45-66). They had previously been randomized either to a diuretic treatment (n = 42), or a beta-blocking agent (n = 41). A 24-hour ambulatory Holter monitoring, and serum potassium, was obtained in all patients, serum magnesium was measured in 35 patients. The mean number of ventricular premature beats (VPBs) and the frequency of complex arrhythmias (19 vs. 5) was significantly higher in the diuretic group (p less than 0.01). The serum potassium was significantly lower (p less than 0.001) in the diuretic group, and there was a significant (p less than 0.005) inverse correlation between the number of VPBs and the serum potassium in all treated patients. The patients with complex arrhythmias were older (p less than 0.01) than the remainder of the patients. No correlation between serum magnesium and VPBs or complex arrhythmias was found. This study demonstrates increased frequency of VPBs in older hypertensive males, treated with diuretics, and that hypokalaemia predisposes to increased cardiac arrhythmias. We conclude that in older mildly hypertensive men hypokalaemia should be avoided.

Evaluation of the Tg.AC assay: specificity testing with three noncarcinogenic pharmaceuticals that induce selected stress gene promoters in vitro and the inhibitory effects of solvent components

Understanding the strengths and limitations of alternative models, such as the Tg.AC assay, for evaluation of the potential carcinogenicity of pharmaceuticals requires assessment of assay specificity through studies that specifically target biologically active compounds that are known to not be carcinogens in rodents. To identify drugs that might provoke a false positive response in the Tg.AC assay, we screened pharmaceuticals for in vitro induction of the gadd153 promoter and the zeta-globin promoter. We have previously found a high correlation between induction of the gadd153 promoter in HepG2 cells and activity in the Tg.AC assay. The three drugs selected through screening 99 noncarcinogenic pharmaceuticals were amiloride, dipyridamole, and pyrimethamine. A 26-week skin paint study was conducted in hemizygous Tg.AC mice with the three drugs at two doses selected by a 4-week dose range finding study. Evidence of systemic toxicity was observed in animals dosed chronically with pyrimethamine or amiloride, but no skin papillomas were observed in mice treated with amiloride, dipyridamole, or pyrimethamine for 26 weeks. All male mice and 80% of female mice treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) in acetone developed a maximal tumor burden. However, mice treated with TPA in a vehicle containing 2.4% DMSO had greatly reduced incidences of papillomas. In summary, the correct negative response was shown in the Tg.AC assay for three noncarcinogenic pharmaceuticals, which adds further favorable evidence of appropriate specificity of this model system. However, vehicle composition must be carefully selected because the outcome of this assay can be confounded by certain commonly used solvents.

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.

[Effectiveness of felodipine in hypertensive patients with mild cerebral cognition disorders in a randomized double-blind study]

BACKGROUND AND OBJECTIVE

Cognitive impairment occurs more frequently in hypertensives than in normotensive individuals. Early signs of cognitive impairment are predictors of dementia in late life. Felodipine is capable of almost normalizing plasma viscosity, which is elevated in most of hypertensive patients, thus improving microcirculation. The aim of this study was to evaluate whether this hemorheologic property of felodipine in addition to its blood pressure lowering effect can improve cognitive performance in hypertensive patients.

PATIENTS AND METHODS

Randomized, double-blind comparison between felodipine 10 mg and hydrochlorothiazide 50 mg amiloride 5 mg (HCT/amiloride) in patients 50-70 years of age with impaired cognitive function (c.l. test 1-2 points) and with resting blood pressure values of diastolic > 95 and < or = 115 mmHg and/or systolic > 160 and < or = 210 mmHg. Blood pressure measurements and evaluation of total short term storage capacity were done at the beginning and after 12 weeks of treatment.

RESULTS

31 patients (14 felodipine and 17 HCT/amiloride) were included in the per protocol analysis. Blood pressure values at the beginning and after 12 weeks of treatment were (mmHg): for felodipine systolic 168 +/- 4 and 150 +/- 6 (p < 0.01), diastolic 108 +/- 3 and 88 +/- 4 (p < 0.001). For amiloride/HCT systolic 173 +/- 8 and 150 +/- 10 (p < 0.01), diastolic 105 +/- 5 and 88 +/- 5 (p < 0.001). Short term storage capacity improved by 15 +/- 6 bits during felodipine treatment (p < 0.001) and by 9 +/- 9 bits during amiloride/HCT treatment (p < 0.05). Thus cognitive improvement was superior by 67% in the felodipine group compared to amiloride/HCT (p < 0.05).

CONCLUSION

In this study a pronounced improvement of mental performance occurred in patients treated with felodipine. Since the cognitive gain was significantly superior to amiloride/HCT treatment there must be an additional blood pressure-independent effect of felodipine, such as enhancing microcirculation. Whether these properties possibly counteract the development of dementia in hypertensives has to be evaluated in long term studies in more patients.

Severe hyponatraemia in an amiloride/hydrochlorothiazide-treated patient

A 85-year-old woman treated with, among other drugs, a thiazide diuretic presented with a severe hyponatraemia. She met several of the criteria for SIADH and, besides drugs, no cause for SIADH was found. After stopping the thiazide diuretic and restricting fluid intake the patient recovered fully. It was later proved that the thiazide was the cause of the water intoxication by rechallenging the patient with a single dose of amiloride/hydrochlorothiazide 5/50 mg. This "thiazide provocation test" showed its usefulness in the differential diagnosis of suspected SIADH. Moreover, the test demonstrated the paradoxal effect of thiazide diuretics to cause water retention in susceptible patients.

Rapid life-threatening hyperkalemia after addition of amiloride HCl/hydrochlorothiazide to angiotensin-converting enzyme inhibitor therapy

STUDY OBJECTIVE

To highlight the dangers of a precipitous rise in serum potassium levels in patients at risk for renal insufficiency, already receiving an angiotensin-converting enzyme (ACE) inhibitor, who are given a potassium-sparing diuretic.

METHODS

We conducted a retrospective chart review of five patients who were taking the above combination of medications who were seen in our ED with hyperkalemia.

RESULTS

All five patients had diabetes and were older than 50 years of age. Except for one patient, they had some degree of renal impairment and all were receiving an ACE inhibitor. Each had amiloride HCl/hydrochlorothiazide added to their therapeutic regimen 8 to 18 days before presenting to our ED with hyperkalemia. Potassium levels were between 9.4 and 11 mEq/L in 4 of the patients; 2 did not respond to resuscitation measures.

CONCLUSION

The concomitant use of ACE inhibitor and potassium-sparing diuretic therapy should be avoided. If impossible, weekly monitoring of both renal function and serum potassium should be performed. In the ED patients who are receiving such a combination should receive immediate ECG monitoring.

Pharmacokinetics of amiloride after inhalation and oral administration in adolescents and adults with cystic fibrosis

STUDY OBJECTIVE

To compare the pharmacokinetics and systemic exposure of nebulized and oral amiloride in adolescents and adults with mild to moderate cystic fibrosis (CF).

DESIGN

Open-label, randomized, two-way crossover, single-dose pharmacokinetic study.

SETTING

University hospital clinical research unit.

PATIENTS

Nine adolescents and 10 adults with mild to moderate CF (forced expiratory volume in 1 sec > or = 50% predicted, Brasfield score > or = 15).

INTERVENTIONS

Patients received amiloride solution orally (10 mg of amiloride 1-mg/ml solution) and by inhalation [4.5 ml amiloride of 1-mg/ml solution in 12% saline (approximately 3.8 mmol/L) by DeVilbiss 646 nebulizer] during two study phases separated by a 7- to 28-day washout period. Serial blood and urine samples were collected for 48 and 72 hours, respectively.

MEASUREMENTS AND MAIN RESULTS

After oral dosing, the mean +/- SD maximum peak concentration (Cmax) was 20.6 +/- 10.0 ng/ml at 3.2 +/- 1.2 hours in adults and 21.7 +/- 4.88 at 2.9 +/- 0.6 hours in the adolescents. Mean area under the concentration-time curve (AUC) from time zero to infinity hours was 275 +/- 115 and 254 +/- 60 ng.hr/ml in the adult and adolescent groups; half-life was 16.0 +/- 0.7 and 13.4 +/- 1.4 hours, respectively. After nebulization, 14 of 19 subjects exhibited two concentration peaks (Cmax1 and Cmax2) with mean values of 1.57 +/- 1.67 ng/ml at 0.5 +/- 0.2 hours and 1.37 +/- 1.21 ng/ml at 4.0 +/- 1.0 hours for adults, and 1.49 +/- 0.99 ng/ml at 0.5 +/- 0.1 hours and 1.52 +/- 0.81 ng/ml at 3.3 +/- 0.5 hours for adolescents. Estimated mean +/- SD dose nebulized was 1.91 +/- 0.66 and 2.28 +/- 0.30 mg in the adult and adolescent groups, respectively. Mean +/- SD AUC from time zero to the last measurable plasma amiloride concentration after inhalation was 14.4 +/- 17.6 and 15.4 +/- 10.1 ng.hr/ml in the adults and adolescents. No significant adverse events occurred during the study. Pharmacokinetic parameters were not statistically different between the adolescent and adult groups by route of administration. However significant differences in peak amiloride concentration, AUC, and urinary amiloride excretion were evident when comparing oral versus inhalation administration within each group.

CONCLUSIONS

Mean amiloride plasma concentration peaks and AUC after inhalation were significantly lower than after oral dosing. In addition, the second amiloride plasma concentration peak may be due to oral ingestion of the nebulized amiloride, whereas the earlier Cmax1 after inhalation may be due to pulmonary absorption of amiloride. These results suggest that single-dose amiloride inhalation in patients with mild to moderate CF results in minimal systemic exposure compared with oral dosing, and that drug disposition is similar in adolescents and adults with CF.

[Potassium-sparing diuretics (spironolactone, triamterene, amylorid)]

The group of drugs, so-called "potassium sparing diuretics" represent an important part of our modern therapeutic arsenal. Their "weak diuretic" properties are especially beneficial in cirrhotic patients with ascites, when highly effective loop diuretics may be hazardous. Potassium sparing diuretics have not only the advantage of avoiding potassium loss, but can potentiate the effects of diuretics acting in distal tubules and Henle's loop also. They may be combined by each other or ACE inhibitors too, taking the necessary precautions and laboratory monitoring. Their indications include the hypertension and special diseases as Conn's, Bartter's, Liddle syndromes and hirsutism. The broad clinical usefulness justifies the drug inventory ambition to develop new, more effective potassium sparing compounds without side effects. Authors overview their main clinicofarmacological properties, therapeutical indications alone or in combinations and their potential side effects.

Acute safety and effects on mucociliary clearance of aerosolized uridine 5'-triphosphate +/- amiloride in normal human adults

Impaired mucociliary clearance contributes to the pathophysiology of several airways diseases including cystic fibrosis, asthma, and chronic bronchitis. Extracellular triphosphate nucleotides (adenosine 5'-triphosphate [ATP], uridine 5'-triphosphate [UTP]) activate several components of the mucociliary escalator, suggesting they may have potential as therapeutic agents for airways diseases. We conducted initial (Phase I) studies of acute safety and efficacy of aerosolized UTP alone and in combination with aerosolized amiloride, the sodium channel blocker, in normal human volunteers. Safety was assessed by measurement of pulmonary function. Neither UTP alone nor in combination with amiloride caused any clinically significant adverse effects on airway mechanics, (subdivisions of) lung volumes, or gas exchange. Acute efficacy of UTP and amiloride alone and in combination, was assessed by measuring changes in the clearance of inhaled radiolabeled particles. A 2.5-fold increase in mucociliary clearance was seen in response to UTP alone and in combination with amiloride. We conclude that aerosolized UTP +/- amiloride clearly enhances mucociliary clearance without acute adverse effects in normal adults, and may have therapeutic potential to enhance airways clearance in diseases characterized by retained airways secretions.

A longitudinal study of factors predicting change in cognitive test scores over time, in an older hypertensive population

This study aims to describe factors associated with cognitive decline among 2584 subjects, aged 65-74, who were followed up for 54 months in the Medical Research Council Elderly Hypertension Trial (1982-1989). The subjects completed a cognitive test, the Paired Associate Learning Test (PALT), five times over this period. Decline on the PALT was associated with advanced age, male sex, rural residence, depression and low intelligence. These effects were modified by gender and level of pre-morbid intelligence. Advanced age, rural residence and number of cigarettes smoked daily were only associated with PALT decline among women of below median intelligence. The association between depression and PALT decline was only apparent in women of below median intelligence and men of above median intelligence. While these findings are consistent with other research into cognitive decline, they differ in some ways from reported risk factors for dementia, suggesting aetiological separateness. That women were more vulnerable than men to the effects of age and smoking raises the question of the impact on cognition of accelerated atherosclerosis after the menopause.

Granulomatous interstitial nephritis associated with hydrochlorothiazide/amiloride

A 74-year-old woman developed acute renal failure and granulomatous interstitial nephritis associated with hydrochlorothiazide/amiloride. On stopping the drug the renal function improved, but not significantly. Around 20 months after prednisone administration, the renal function had stabilized, with a moderate degree of renal insufficiency. The case is discussed, and some aspects of acute interstitial nephritis induced by diuretics are briefly reviewed.

Amiloride-quinidine interaction: adverse outcomes

OBJECTIVES

Previous studies have reported beneficial antiarrhythmic effects when selected drugs were combined. The purpose of this study was to assess whether a favorable interaction would occur with amiloride and quinidine.

DESIGN

The antiarrhythmic and electrophysiologic effects of quinidine alone and in combination with amiloride were assessed in 10 patients with inducible sustained ventricular tachycardia. Parallel electrophysiologic studies assessed this drug combination in guinea pig papillary muscle.

RESULTS

None of the patients had adverse effects during quinidine monotherapy. However, seven of 10 patients had adverse responses to the combination treatment: three patients had suppression of inducible ventricular tachycardia during quinidine monotherapy but had sustained ventricular tachycardia induced during combination treatment; three other patients had somatic side effects that resulted in discontinuation of the combination therapy but were absent during quinidine monotherapy; and one patient had 12 episodes of sustained ventricular tachycardia during this combination therapy. The patient had no such response during monotherapy. Surface QRS duration was significantly more prolonged during combination therapy than during monotherapy. Parallel electrophysiologic effects assessed this drug combination in guinea pig papillary muscle. The combination of amiloride (1 mumol/L) and quinidine (10 mumol/L) synergistically decreased the maximum rate of rise of phase 0 of the action potential (Vmax) (43 +/- 12 V/sec) compared with quinidine alone (24 +/- 9 V/sec) because of a greater degree of tonic block of Vmax (14% +/- 6%) as compared to quinidine alone (3% +/- 3%) with no significant change in action potential duration.

CONCLUSIONS

Amiloride exaggerates the effects of quinidine on QRS duration in patients and on Vmax during in vitro study, which implies that the proarrhythmic effect of the combination of amiloride and quinidine may be associated with synergistic increase in sodium channel blockade.

Antihypertensive efficacy and tolerability of different drug regimens in isolated systolic hypertension in the elderly

The pharmacological treatment, mainly based on diuretics, of isolated systolic hypertension (ISH) has recently been shown to reduce the risk of stroke and coronary heart disease in the elderly. The purpose of this study was to compare the antihypertensive effect and tolerability of different drug regimens in elderly subjects with ISH (systolic blood pressure--SBP-- > or = 160 mmHg and diastolic blood pressure--DBP-- < 90 mmHg). A multicentre, randomized, controlled open trial was planned in the general practice setting. Four widely used treatment schedules were tested: hydrochlorothiazide 25 mg plus amiloride 2.5 mg (H+Am), nifedipine slow release 20 mg (N), atenolol 50 mg (At) and atenolol 25 mg plus chlorthalidone 6.25 mg (At+C). After a baseline evaluation, 308 patients (76.3% female, mean age 75.3 +/- 7.1 years) were randomized and followed up for 6 months. After 3 months the drug dosage was doubled if the systolic blood pressure goal (SBP < 160 mmHg and SBP reduction of at least 20 mmHg) had not been reached. Ninety-four subjects (30.5%) presented contraindications to beta-blockers. At the 3rd- and 6th-month visits all treatment groups, except At, showed a significant reduction in SBP compared to the control group; DBP showed no significant reduction in any group at any time. At the end of the follow-up the percentage of hypertensives who had reached the BP goal was 14.6% in the control group, 52.9% in H+Am, 54.8% in N, 28.6% in At and 52.2% in At+C.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of moduretic on plasma lipid and lipoprotein levels in hypertensive African patients

Twenty patients with essential hypertension aged 39-70 years, underwent 20 weeks (short-term) and 30 weeks (long-term) lipid and lipoprotein assessment following moduretic (combination of hydrochlorothiazide and amloride) therapy. Moduretic caused adverse alterations in plasma lipid and lipoprotein concentrations at 20 weeks, characterized by increases in total cholesterol (TC) (9-23%), low-density lipoprotein-cholesterol (LDL-C) (18-42%), Triglycerides (TG) (12-26%) and LDL-C/HDL-C (36-92%), as well as decreases in high density lipoprotein-cholesterol (HDL-C) (-14 to -26%) and HDL-C/TC (-23 to -39%). For 12 patients who were continued on the same therapy for the longer period of 30 weeks, the adverse effects were less pronounced when compared with the short-term effects. The increases in TC (9.6%), in LDL-C (21%), and in LDL-C/HDL-C (48%), and the decreases in the mean HDL-C (-20%), and in HDL-C/TC (-25%), were all significant. In contrast, the slight increase in TG noted during the long-term moduretic therapy was not significant. Our data suggest that moduretic therapy induces altered lipid-lipoprotein patterns in hypertensive patients. However, the possible influence of baseline cholesterol concentration and the duration of therapy, may be important factors in the lipid response to moduretic therapy.

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.

[Amiloride inhalation therapy in mucoviscidosis]

The defective regulation of the secretory chloride channel and the accelerated rate of sodium absorption in the airway epithelia of patients with cystic fibrosis (CF) contribute to the dehydration of airway secretions which is responsible for secondary damage in the respiratory tract. The sodium-blocker amiloride inhibits sodium absorption depending on the dosage of the drug. This effect is documented by means of measuring transepithelial potential difference which is decreased following to inhalative amiloride administration in CF patients. Clinical long term efficiency has been shown to be probable, but has to be confirmed. Investigation in this field is difficult, because there are some other important factors which influence viscosity of mucus. The use of amiloride can best be evaluated, if it is given immediately after birth. However, the answer to some important questions has to be found before.

A comparison of the potassium and magnesium-sparing properties of amiloride and spironolactone in diuretic-treated normal subjects

1. The relative potencies of amiloride (5 and 20 mg) and spironolactone (25 and 100 mg) for plasma and erythrocyte electrolytes were investigated in a double-blind, randomised, balanced, crossover study in 12 normal men treated concomitantly with hydrochlorothiazide 100 mg daily for 1 week. 2. Participants satisfied an a priori requirement for a fall in plasma potassium concentration of at least 0.5 mmol l-1 after 7 days of treatment with hydrochlorothiazide alone. 3. After hydrochlorothiazide alone, plasma potassium and sodium concentrations fell (P < 0.001). There were associated reductions in erythrocyte sodium (P < 0.01). Plasma magnesium concentration did not change, although erythrocyte magnesium decreased (P < 0.001). 4. Both amiloride and spironolactone attenuated the thiazide-induced fall in plasma potassium (relative potency, amiloride:spironolactone 10:1, 95% confidence interval 6.3-16.2:1). Amiloride but not spironolactone was associated with a dose-related increase in plasma magnesium; a relative potency estimation was precluded. There was little evidence of influences of amiloride or spironolactone on erythrocyte electrolytes. 5. On a weight basis, amiloride is ten times more potent than spironolactone as a potassium-sparing agent in diuretic-treated subjects but neither agent had major effects on erythrocyte potassium. The drugs may have divergent actions on magnesium handling; hydrochlorothiazide alone had no influence on plasma magnesium.

Muscular paralysis and ventilatory failure caused by hyperkalaemia

We report the history of a diabetic man presenting with hyperkalaemia and rapidly progressing muscular paralysis with severe respiratory embarrassment. His symptoms resolved rapidly with reduction of the serum potassium concentration. Similar cases have been reported previously but this is a problem that few will have encountered and is a diagnosis which should not be overlooked before artificial ventilation is commenced.

Impaired salivary gland function after radiotherapy compounded by commonly prescribed medications

Impaired salivary gland function can be a major cause of late morbidity following the treatment of head and neck cancer with radiotherapy. A large number of commonly prescribed medications can also reduce salivary gland function. We report three patients with already impaired salivary gland function following successful radiotherapy in whom additional prescribed medication led to an increased reduction in salivary flow, thus further impairing the quality of life of these patients. Stopping the medication resulted in subjective and objective improvement in salivary gland function.

Preventable sudden death in patients receiving angiotensin converting enzyme inhibitors and loop/potassium sparing diuretic combinations

Angiotensin-converting-enzyme inhibitors are frequently used in conjunction with diuretics in the treatment of congestive cardiac failure. We report two cases in which use of a proprietary combination diuretic containing a loop diuretic and potassium sparing agent with an angiotensin converting enzyme inhibitor was associated with hyperkalaemic cardiac arrest. Successful resuscitation from the arrest permitted elucidation of its mechanism. We believe that this outcome has not previously been reported, and emphasise the importance of electrolyte monitoring in patients receiving angiotensin converting enzyme inhibitors particularly if prescribed in addition to fixed combination proprietary diuretics.

A double-blind comparison of perindopril and hydrochlorothiazide-amiloride in mild to moderate essential hypertension

The aim of this 3-month double-blind multicenter trial was to compare the antihypertensive efficacy and tolerability of the ACE inhibitor perindopril with those of a diuretic combination. After 1 month of receiving placebo, 165 patients with essential hypertension were randomised to perindopril 4 mg (n = 82) or to 50 mg hydrochlorothiazide + 5 mg amiloride (n = 83). The patients were treated for 3 months with monthly assessments, "uncontrolled" patients (DBP greater than 90 mm Hg) had their dosage doubled and then, if necessary, atenolol 50 mg was added. At the end of the 3-month study, mean decreases in supine and standing systolic and diastolic blood pressures were similar in both groups. In the perindopril group, BP control was obtained in 56% of the patients with the 4 mg dosage and required an increase to 8 mg alone in 16% and with atenolol in 5%. The corresponding percentages in the diuretic group were 48, 23 and 13%. The overall percentage of "controlled" patients was similar in the 2 groups, respectively 78 and 84%. The nature and incidence of complaints were comparable in the 2 groups. Adverse laboratory changes were more frequent in the diuretic group: decrease in blood sodium (140.5 vs 139.1 mmol/l; P less than 0.01), potassium (4.2 vs 3.9 mmol/l; P less than 0.01) with 10 patients having significant hypokalemia, increase in blood urea, triglycerides and uric acid. By contrast, a transient increase in blood potassium with a decrease in triglycerides was observed in the perindopril group.

[Pulmonary edema induced by hydrochlorothiazide/amiloride (Moduretic)]

A 44-year-old woman was seen on three separate occasions for acute pulmonary edema which had developed 30 minutes after ingestion of a single hydrochlorothiazide-amiloride (Moduretic) tablet. Eighteen cases of hydrochlorothiazide-induced pulmonary edema have been reported previously. Clinical findings and investigations in the present and previous cases indicate a noncardiogenic cause for the pulmonary edema. Increased pulmonary vascular permeability is probably involved. So far, attempts to demonstrate an immunological mechanism have failed and the pathophysiology remains uncertain. The reaction may be difficult to differentiate from left ventricular failure in patients with cardiac disease. Attention should be drawn to this severe but rare side effect of a frequently used diuretic.

Cardiac conduction defects associated with hyponatremia

Cardiac conduction defects have not been previously described in association with hyponatremia, although in patients with congestive heart failure the frequency of ventricular premature beats was found to correlate to the severity of hyponatremia. We describe three patients with second-degree or complete atrioventricular (AV) block which occurred during or shortly after an episode of severe hyponatremia. The first had thiazide-induced hyponatremia while on amiodarone. In the second, definite etiology for hyponatremia which was associated with longstanding polydipsia could not be established. The third had ischemic heart disease and intermittent conversion of his first-degree to second-degree AV block while hyponatremic after diuretics use. Although it is usually difficult to single out hyponatremia as the cause of conduction defects which usually occur in the presence of cardiac disease, potent medications or other electrolyte abnormalities, we suggest that hyponatremia may play a role in the pathogenesis of conduction defects in the diseased heart.

Acute hyponatraemia following total hip replacement

An elderly woman who had been taking a fixed-dose combination of a thiazide and potassium-sparing diuretic for eight days, became severely hyponatraemic following total hip replacement. Her hyponatraemia resolved with fluid restriction, intravenous normal saline, and withdrawal of the drug. Hyponatraemia is a well-described side-effect of diuretic therapy; however, we are not aware of any previous reports of this condition developing acutely in the postoperative state. We attribute this to the natriuretic nature of the drug, compounded by the postoperative, anti-diuretic surge which itself may have been exacerbated by the drug. We thus advise caution in the use of this preparation in the elderly patient about to undergo major surgery.

Bumetanide/amiloride ('Burinex A'): a new combined preparation for the control of patients with congestive cardiac failure

Two hundred and thirty-three patients (66 males and 167 females), aged 24 to 92 years, with congestive cardiac failure were entered into a long-term study to evaluate the efficacy and tolerability of treatment with a fixed dose combination tablet containing 1 mg bumetanide and 5 mg amiloride. One hundred and fifty-five patients were treated for 52 weeks. The daily dosages were 1 tablet (113 patients), 2 tablets (35 patients), 3 or 4 tablets (7 patients). Treatment was associated with a marked reduction in the prevalence of ankle oedema, dyspnoea and pulmonary crepitations, and with statistically significant decreases in body weight, pulse rate and calf measurement. Mean serum potassium showed a small but statistically significant increase, but serious hyperkalaemia was not encountered. Although serum sodium decreased, serious hyponatraemia did not occur. No clinically significant effects on hepatic, renal or haemopoietic function were observed. Minor adverse effects, most of which resolved spontaneously, were reported by 60 patients. Only 14 (6.0%) patients ceased treatment because of adverse effects.

Antihypertensive efficacy and influence on physical activity of three different treatments in elderly hypertensive patients

The antihypertensive efficacy and subjective and physical tolerability of three different pharmacological treatments (metoprolol, captopril and the combination of hydrochlorothiazide + amiloride) were compared with placebo in 36 elderly hypertensives (aged 61-79 years), according to a Latin-square double-blind design. The placebo and the active treatments were administered for 2 months. Seated blood pressure was significantly reduced by all the pharmacological treatments compared with placebo, but only metoprolol significantly reduced the heart rate. No haematological or biochemical changes were observed during the study. Physical fitness, evaluated as endurance in a standard cycle ergometer exercise test, was slightly decreased after the treatment with metoprolol and the diuretic combination and slightly improved after treatment with captopril. Subjective tolerability, evaluated by a check-list of symptoms, was better during the active therapies, and in particular during the captopril treatment, than during the placebo treatment. Our results indicate that all three active treatment regimens significantly reduce blood pressure in elderly hypertensives and that captopril appears slightly better tolerated physically and subjectively.

Ibopamine versus hydrochlorothiazide/amiloride in patients with mild congestive heart failure. SK & F Ibopamine Working Group

The clinical efficacy and safety of ibopamine and diuretic therapy were compared in a multicenter, multinational, parallel, positive-controlled, randomized, double-blind, 12-week study, involving 103 patients with mild CHF (NYHA Class II). Body weight, NYHA functional class, symptom assessment scores, laboratory blood tests, and exercise testing were evaluated at baseline at interim visits and at the end of 12 weeks. Clinical events were monitored throughout the study. There was no difference in any of the considered parameters between the two patient groups at baseline and at the end of the 12-week evaluation. A trend of improvement in clinical conditions that did not reach statistical significance was noted in each group throughout the study, as a probably "trial effect." Five patients on ibopamine had severe clinical events leading to drug discontinuation (CHF worsening, ventricular tachycardia, elevation of liver transaminases, headache, gastrointestinal disorders) and five on diuretic therapy experienced serious side effects (skin rash, palpitation, atrial fibrillation, elevation of liver transaminases, manic episode). One patient died while on diuretic therapy. Only headache and skin rash were considered to be related to the therapy (ibopamine and diuretic therapy, respectively). Our trial suggests that ibopamine can be safely and effectively used as an alternative for diuretics for up to 3 months in patients with mild CHF.

Comparison of indapamide and hydrochlorothiazide plus amiloride as a third drug in the treatment of arterial hypertension

In a randomized, double-blind crossover trial, indapamide (IND) 2.5 mg and hydrochlorothiazide 25 mg + amiloride 2.5 mg (HCTZ + A) were found to be equally effective in reducing blood pressure (BP) in 13 patients with moderate to severe hypertension already receiving chronic treatment with a beta blocker and a vasodilatator (supine BP during run-in: 169/103 +/- 21/5 mmHg; on IND: 149/91 +/- 21/14 mmHg; on HCTZ + A 144/88 +/- 23/5 mmHg). Both drugs induced insignificant reductions in body weight, and no change in plasma volume was seen. Serum potassium was significantly reduced on both regimens--the values recorded on IND being significantly lower than those seen on HCTZ + A. Values below 3.0 mmol/l were found in two patients receiving IND, but no subjective side effects were reported. Hyperuricemia occurred with the same frequency on both regimens. It is concluded that IND, just like the thiazide diuretics, is useful as the third drug in patients needing triple drug therapy to control BP, but metabolic adverse effects are not avoided by the choice of this drug.