The effect of thiazides, chlorthalidone and furosemide on muscle electrolytes and muscle glycogen in normal subjects

The masters athlete and use of antihypertensive medications

Hypertension is the most common cardiovascular condition in recreational athletes, especially older (masters) athletes. The interacting effects of hypertension, cardiac adaptation to endurance training, and antihypertensive medications on exercise performance are complex and of relevance to athletes, trainers, and health care providers. Cardiac adaptations occur in response to aging and endurance training, and findings may overlap with pathologic cardiac remodeling. This review summarizes the influence of antihypertensive medications on exercise performance, which can include both hemodynamic and metabolic effects, and includes practical considerations in choice of antihypertensive agent for the masters endurance athlete. Whereas the overriding priority for choice of antihypertensive is control of hypertension and improving clinical outcomes, other considerations regarding effects on exercise performance may also influence the choice of agent.

Medications that cause weight gain and alternatives in Canada: a narrative review

BACKGROUND

The cause of the obesity epidemic is multifactorial, but may, in part, be related to medication-induced weight gain. While clinicians may strive to do their best to select pharmacotherapy(ies) that has the least negative impact on weight, the literature regarding the weight effects of medication is often limited and devoid of alternative therapies.

RESULTS

Antipsychotics, antidepressants, antihyperglycemics, antihypertensives and corticosteroids all contain medications that were associated with significant weight gain. However, there are several medication alternatives within the majority of these classes associated with weight neutral or even weight loss effects. Further, while not all of the classes of medication examined in this review have weight-favorable alternatives, there exist many other tools to mitigate weight gain associated with medication use, such as changes in dosing, medication delivery or the use of adjunctive therapies.

CONCLUSION

Medication-induced weight gain can be frustrating for both the patient and the clinician. As the use of pharmaceuticals continues to increase, it is pertinent for clinicians to consider the weight effects of medications prior to prescribing or in the course of treatment. In the case where it is not feasible to make changes to medication, adjunctive therapies should be considered.

Potassium in skeletal muscle in untreated primary hypertension and in chronic renal failure, studied by X-ray fluorescence technique

Muscle biopsy specimens form 22 patients with primary hypertension, 10 patients with chronic renal failure and 21 healthy normotensive controls were analyzed using a Kevex 0600 X-ray spectrometer. Muscle potassium (MK), calcium (MCa), sulphur (MS) and phosphorus (MP) were determined. In the patients with primary hypertension, MK was decreased compared to the controls (p less than 0.001), MCa was increased (p less than 0.05), MS was decreased (p less than 0.05) and no difference was seen in MP. In the patients with chronic renal failure, MK was decreased compared to the controls (p less than 0.001), MCa showed no difference compared to the controls, whereas both MP and MS were lower (p less than 0.05 and p less than 0.001). It was concluded that intracellular potassium is low both in primary hypertension and chronic renal failure. In chronic renal failure the potassium decrease is probably secondary to loss of cellular potassium capacity, whereas in primary hypertension an inhibition of the sodium, potassium, adenosine triphosphatase is suggested as the cause of the low potassium.

Hypokalemia--clinical spectrum and etiology

This paper is intended to give a review of the etiology and symptoms of potassium deficiency in man, as an introduction to the section on potassium and cardiac arrhythmias of this symposium. A review is given of different conditions where hypokalemia and/or total potassium deficiency is or might be part of the clinical picture, such as conditions with insufficient dietary intake, gastrointestinal potassium losses (e.g. vomiting, fistulas, malabsorption, abuse of laxatives and diarrhea), and renal potassium losses (e.g. primary and secondary hyperaldosteronism, Cushing's syndrome, intake of licorice, diabetic coma, renal disease, diuretic treatment and l-dopa treatment). Common symptoms of hypokalemia and/or potassium deficiency are reviewed as well, such as general and unspecific symptoms (e.g. tiredness, lack of concentration, lack of appetite and vomiting), and symptoms from the heart, kidneys and skeletal muscle.

Ventricular extrasystoles and intracellular electrolytes in hypokalemic patients before and after correction of the hypokalemia

Fifty-four initially hypokalemic patients, 43 of whom were on diuretic treatment, were given potassium supplementation until they showed a repeatedly normal serum potassium level. Muscle specimens obtained by percutaneous biopsy revealed that there were no concomitant increases in muscle potassium content, nor in intracellular potassium concentration, except in the very small group (6 patients) with a muscle magnesium content of greater than or equal to 3.95 mmol/100 g fat free dry solids (FFDS) and an initially lower muscle potassium content (less than or equal to 39.9 mmol/100 g FFDS). ECG, registered for 3 hours on a portable ECG tape recorder before and after correction of the serum potassium level, showed no change in the frequency of ventricular ectopic beats.

Effect of saluretic therapy on muscle content of water and electrolytes in relation to hemodynamic variables

Muscle content of water and electrolytes (needle biopsy), intraarterial BP and cardiac output (dye dilution technique) were measured in 12 patients with essential hypertension before and after 4 months of mefruside therapy (25 mg/day). Before therapy there were no significant differences in muscle tissue electrolyte and water content compared with normotensive subjects. No correlation was found between central hemodynamic variables and the electrolyte and water content of muscle tissue either before or after therapy. After 4 months of mefruside therapy, muscle tissue water showed a mean decrease which was not significant. Serum potassium and muscle potassium content decreased significantly but there was no significant change in intracellular potassium concentration. Intracellular sodium concentration increased significantly, while muscle sodium content showed a mean increase which was not statistically significant. The change in intracellular sodium concentration showed a significant negative correlation with the decrease in mean arterial BP. The change in total cellular water content showed a significant negative correlation to the changes in total peripheral vascular resistance. Saluretic therapy seems to induce counterregulatory mechanisms that interfere with the hypotensive effect.

Problems with potassium and magnesium in diuretic-treated patients

Treatment with thiazides and loop diuretics increase the urinary excretion of potassium and magnesium and the body content of these ions are reduced after long-term treatment. The diuretic-induced magnesium deficiency influences the potassium metabolism. Magnesium is a necessary activator of Na-K-ATPase, which supplies the Na-K pump with energy. Lack of magnesium will therefore impair the pumping of sodium out of the cell and of potassium into the cell. The change of the relationship between extra and intracellular potassium may induce cardiac arrhythmias. Certain groups of patients, such as patients on digitalis therapy, patients with secondary hyperaldosteronism, elderly patients with insufficient dietary habits, and heavy drinkers, run an additional risk of developing potassium/magnesium disturbances. In young patients with uncomplicated essential hypertension, the risk is probably very small.

Effect of chronic treatment with enalapril on glucose tolerance and serum insulin in non-insulin-resistant Japanese patients with essential hypertension

The effect of enalapril, an angiotensin converting enzyme inhibitor, on glucose tolerance and serum insulin response to a glucose load has been evaluated in 8 non-obese patients (3 women and 5 men) with untreated essential hypertension (WHO Stage I or II) and without insulin resistance. Following a 2-month run-in control period, each patient received oral enalapril 10 mg once daily for 6 months, and an intravenous glucose tolerance test (IVGTT) was performed at the end of the run-in control and active treatment periods. Treatment with enalapril significantly lowered both the systolic and diastolic blood pressures. The response of plasma glucose to the IVGTT, glucose disappearance rate (k-value) and area under the serum insulin concentration time curve were comparable between the two phases. The results suggest that long-term treatment with enalapril has no effect on glucose tolerance in non-obese, non-insulin-resistant patients with mild-to-moderate essential hypertension.

Insulin action and hepatic glucose cycling in essential hypertension

Peripheral insulin resistance is a feature of essential hypertension, but there is little information about hepatic insulin sensitivity. To investigate peripheral and hepatic insulin sensitivity and activity of the hepatic glucose/glucose 6-phosphate (G/G6P) substrate cycle in essential hypertension, euglycemic glucose clamps were performed in eight untreated patients and eight matched controls at insulin infusion rates of 0.2 and 1.0 mU.kg-1.min-1. A simultaneous infusion of (2(3)H)- and (6(3)H)glucose, combined with a selective detritiation procedure, was used to determine glucose turnover, the difference being G/G6P cycle activity. Endogenous hepatic glucose production (EGP) determined with (6(3)H)glucose was similar in hypertensive and control groups in the postabsorptive state (11.0 +/- 0.3 v 10.9 +/- 0.3 mumol.kg-1.min-1) and with the 0.2 mU insulin infusion (4.9 +/- 0.5 v 4.0 +/- 0.8 mumol.kg-1.min-1). With the 1.0 mU insulin infusion, glucose disappearance determined with (6(3)H)glucose was lower in the hypertensive group (21.8 +/- 2.4 v 29.9 +/- 2.4 mumol.kg-1.min-1, P less than .001). G/G6P cycle activity was similar both in the postabsorptive state (2.2 +/- 0.4 v 2.7 +/- 0.4 mumol.kg-1.min-1) and during insulin infusion (0.2 mU, 2.5 +/- 0.3 v 2.9 +/- 0.4; 1.0 mU, 4.7 +/- 0.3 v 5.3 +/- 1.1 mumol.kg-1.min-1 for hypertensive and control groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the effects of hydrochlorothiazide and captopril on glucose and lipid metabolism in patients with hypertension

It has been suggested that the metabolic side effects of antihypertensive drugs are responsible for their failure to reduce cardiovascular morbidity in patients with hypertension. Therefore, in 50 patients with essential hypertension, we performed a randomized, double-blind, crossover study comparing the effects of carbohydrate and lipid metabolism of captopril (mean [+/- SD] dose, 81 +/- 24 mg per day) and hydrochlorothiazide (40 +/- 12 mg per day) over two four-month treatment periods. Captopril increased the insulin-mediated disposal of glucose, as compared with placebo, from 5.7 +/- 2.4 to 6.3 +/- 2.5 mg per kilogram of body weight per minute (P less than 0.05), whereas hydrochlorothiazide caused a decrease from 6.4 +/- 2.0 to 5.7 +/- 1.9 (P less than 0.01). Captopril had no effect on the basal insulin concentration, but it decreased the late (30- to 90-minute) insulin response to glucose and increased the early (2- to 6-minute) insulin peak. Hydrochlorothiazide increased the basal insulin concentration and the late insulin response to glucose. These findings may be explained by an increase in insulin sensitivity with captopril and a decrease with hydrochlorothiazide. Little or no change was seen in serum lipid or lipoprotein levels during treatment with captopril, whereas hydrochlorothiazide caused significant increases in serum total (5 percent) and low-density lipoprotein (6 percent) cholesterol levels and total (15 percent) and very-low-density lipoprotein (25 percent) triglyceride levels, as compared with placebo (P less than 0.01 for all comparisons). We conclude that hydrochlorothiazide for the treatment of essential hypertension has adverse effects on glucose and lipid metabolism. It is possible, but not proved in this study, that these changes may contribute to the risk for diabetes mellitus and coronary heart disease. In contrast, captopril appears to have beneficial or no effects on glucose and lipid metabolism.

Feline kaliopenic polymyopathy/nephropathy syndrome

The prevalence of hypokalemia in cats has probably been underestimated until recently. Like many other "contemporary" diseases, this syndrome is probably not new; however, it is now more easily recognized because of the identification of associated dietary and disease risk factors, clinical signs, and laboratory abnormalities, which have been linked to the expected pathophysiology of potassium depletion in the cat.

Effects of thiazide on erythrocyte sodium and potassium concentrations and Na+K+ATPase in hypertensive patients

The mechanism of thiazide induced sodium and potassium transport across the cell membranes of humans has not been extensively studied. To assess the effects of thiazide diuretics on erythrocyte sodium transport and potassium distribution we measured intracellular sodium and potassium, sodium-potassium ATPase activity (with and without ouabain) and total body potassium in normokalemic and mildly hypokalemic hypertensive patients. We also measured serum and urine sodium, potassium, calcium and magnesium, plasma renin activity and serum aldosterone levels. The study patients, on long-term thiazide, had measurements obtained during, one month after cessation and one month after resumption of thiazide. In this study of normokalemic and mildly hypokalemic hypertensives there were no significant measurement changes, in contrast to previous studies of severely hypokalemic hypertensives. These results suggested that thiazide did not routinely affect erythrocyte active membrane transport and potassium distribution in the absence of severe hypokalemia.

Pharmacokinetics of the loop diuretic piretanide in renal failure

Piretanide 60 mg was administered intravenously over 30 min to 15 men with different degrees of renal failure. The mean piretanide serum concentration at the end of the infusion period was 5.72 +/- 1.51 micrograms/ml. Serum piretanide concentration-time curves declined biexponentially and 24 hours after medication the serum level had fallen to less than twice the detection limit. The terminal half-life ranged from 1.63 to 3.44 h. A relationship to creatinine clearance was not demonstrable. The mean metabolic clearance of piretanide was 107.7 +/- 47.6 ml/min/1.73 m2 body surface area and was the same as that reported for healthy subjects. The renal clearance of piretanide ranged from 3.33 to 43.9 ml/min/1.73 m2 body surface area and very closely correlated with the creatinine clearance (p less than 0.01). Its renal clearance depended principally on active secretion of the drug into the tubule, and glomerular filtration appeared unimportant. There was a close relationship between the amount of piretanide excreted in the urine and the creatinine clearance. Because the diuretic effect of piretanide depends on the concentration of the drug in the tubule, the observed correlation might be of use in evaluating the appropriate dosage of piretanide in patients with renal failure. The present data suggest that single daily doses of piretanide will not result in accumulation, even when high doses are administered to patients with advanced renal failure.

Diuretic-induced hypokalemia

Diuretic therapy is the most common cause of potassium deficiency. Although the extent of potassium deficiency usually does not exceed 200 or 300 mEq, under appropriate circumstances such modest deficiency may have important consequences. Factors that tend to increase the incidence or severity of potassium deficiency in patients who take diuretics include high salt diets, large urine volumes, metabolic alkalosis, increased aldosterone production, and the simultaneous use of two diuretics that act on different sites in the renal tubule. There are many serious complications of potassium deficiency, including cardiac arrhythmias, muscle weakness, rhabdomyolysis, glucose intolerance, and several complications that result directly from increased ammonia production, such as protein and nitrogen wasting and hepatic coma. Emphasized herein are those conditions that impose potential danger in patients with mild hypokalemia. Important factors that identify specific causes of potassium deficiency and its treatment are discussed briefly.

Hypotensive effect of the association atenolol-chlorthalidone in hypertensive diabetics

The authors conducted a clinical investigation in twenty-five patients affected with essential hypertension of mild or moderate grade associated with type II diabetes mellitus, the purpose being to assess the effect of 8 weeks of combined treatment with atenolol (100 mg) and chlorthalidone (25 mg) on arterial blood pressure, heart rate, and glycaemia. It is, indeed, generally known that both beta-blockade agents and diuretics can interfere with carbohydrate metabolism. The results indicate that 92% of the patients treated in this trial had significant reduction of systolic and diastolic blood pressure readings, in the absence of bradycardia or other adverse effects. Glycaemia values were lower at the end of treatment, probably as a result of better diet control during the trial, as suggested by the general tendency to body-weight reduction.

[ATPase activity and sodium transport in erythrocytes of patients with essential hypertension (author's transl)]

The rate constant for erythrocyte "total" sodium efflux was significantly decreased in patients with essential hypertension compared with normotensive controls due to a reduced "ouabain-sensitive" (active) sodium transport. The rate constants for "ouabain-insensitive", "ouabain-insensitive furosemide-sensitive" and "ouabain-insensitive furosemide-insensitive" sodium efflux were not different between hypertensives and normotensives. Ouabain inhibited sodium efflux by 74% and furosemide by a further 13%, both in hypertensives and in normotensives. The reduced rate constant for active erythrocyte transport in patients with essential hypertension was due to a diminished Na-K-ATPase activity demonstrable in hemolyzed and dialyzed erythrocytes. In contrast, in hemoglobin-free red blood cell membranes Na-K-ATPase activity was not different between both groups. Apparently the centrifugation procedure, which is necessary for preparation of hemoglobin-free membranes, leads to a loss of non-hemoglobin proteins, including ouabain-sensitive and ouabain-insensitive ATPase and/or a Na-K-ATPase inhibiting factor. Thus, the results obtained in hemolyzed and dialyzed red blood cells reflect probably better the conditions in the intact erythrocyte than do measurements on hemoglobin-free membranes, suggesting a decreased Na-K-ATPase activity in erythrocytes of essential hypertensives. However, the diminished rate constant for ouabain-sensitive sodium efflux did not result in a measurable increase in erythrocyte sodium indicating that this biochemical abnormality can fully be compensated in moderate essential hypertension without excess salt intake. The cause of the reduced rate constant for ouabain-sensitive sodium efflux is not clear. However, as suggested for sodium-potassium cotransport and for sodium-lithium countertransport it might be determined genetically.

Probable hypothyroid myopathy: glycogen-deficient type 2b fibers

Described herein is a case of hypothyroid myopathy with selective atrophy and glycogen depletion of type 2b fibers shown by light and electron microscopy. Although the pathogenesis of such findings is obscure, it is possible that hypothyroidism in conjunction with a superimposed process might explain paradoxically glycogen-deficient fibers.

Initial potassium loss and hypokalaemia during chlorthalidone administration in patients with essential hypertension: the influence of dietary sodium restriction

To investigate the initial potassium loss and development of hypokalaemia during the administration of an oral diuretic, metabolic balance studies were performed in ten patients with essential hypertension who had shown hypokalaemia under prior oral diuretic treatment. Chlorthalidone (50 mg daily) was given for 14 days. Six patients received a normal-sodium diet and four a low-sodium (17 mmol/day) diet. All patients had a normal initial total body potassium (40K). The electrolyte balances, weight, bromide space, plasma renin activity, and aldosterone secretion rate were measured. In both groups a potassium deficit developed, with proportionally larger losses from the extracellular than from the intracellular compartment. In the normal-sodium group the highest mean potassium deficit was 176 mmol on day 9, after which some potassium was regained; in the low-sodium group the highest deficit was 276 mmol on day 13. The normal-sodium group showed an immediate but temporary rise of the renin and aldosterone levels; in the low-sodium group renin and aldosterone increased more slowly but remained elevated. It is concluded that dietary sodium restriction increases diuretic-induced potassium loss, presumably by an increased activity of the renin-angiotensin-aldosterone system, while sodium delivery to the distal renal tubules remains sufficiently high to allow increased potassium secretion.

Hypokalemic myopathy during treatment with diuretics

Two male patients with severe reversible muscle weakness and excessive potassium deficiency associated with alkalosis during treatment with diuretics are presented. The case reports are further illustrated by the morphologic changes as seen in light and electron microscopic examination of muscle biopsies. Hypokalemia and muscle dysfunction are discussed in relation to other investigations of altered potassium metabolism and myopathy during treatment with certain diuretics.

The effect of hydrochlorothiazide and amiloride administered together on muscle electrolytes in normal subjects

Hydrochlorothiazide, 150 mg daily, and amiloride, 15 mg daily, have been administered together to 10 normal subjects during one week. Muscle biopsies were performed before and after the period of administration of the diuretics and the material was analysed for water and electrolytes. The body weight decreased by 1.9 kg. The serum sodium, chloride and potassium concentrations decreased significantly and standard bicarbonate and blood pH increased. In muscle tissue, extracellular water, chloride and sodium contents and intracellular sodium concentration decreased but the muscle potassium content, the intracellular potassium concentration and the muscle magnesium content were unchanged. A comparison with the results of an earlier study, in which hydrochlorothiazide was given without amiloride, showed that the intracellular potassium depletion and the increase in intracellular sodium concentration, observed with the benzothiazide diuretic, could be fully prevented by simultaneous administration of amiloride. The degree of hypokalemia and alkalosis was also smaller with hydrochlorothiazide + amiloride than with hydrochlorothiazide alone.