Calcium-sparing diuretics

Calcium-sparing diuretics. Diuretics that result in a relatively low rate of excretion of calcium. The sparing effect on calcium can be beneficial in hypocalcaemia. The thiazides and potassium-sparing diuretics are considered to be calcium-sparing diuretics. The thiazides cause a net decrease in calcium lost in urine the potassium-sparing diuretics cause a net increase in calcium lost in urine, but the increase is much smaller than that associated with other diuretic classes. By contrast, loop diuretics promote a significant increase in calcium excretion. This can increase risk of reduced bone density. 

The first inhibitor of NHE, amiloride, was identified in 1982. This drug is a potassium-sparing diuretic that also inhibits the sodium-calcium exchanger and the conductive Na+ channel. Not all the NHE isoforms are inhibited equally by amiloride NHE1 and 2 are responsive, NHE5 is partially responsive and NHE3, 4 and 7 are resistant. Other weak and non-specific inhibitors are clonidine and cimetidine. 

Other drugs that may interact with cardiac glycosides include the following Albuterol, amphotericin B, beta-blockers, calcium, disopyramide, loop diuretics, nondepolarizing muscle relaxants, potassium-sparing diuretics, succinylcholine, sympathomimetics, thiazide diuretics, thioamines, and thyroid hormones. 

Drugs that may affect cyclosporine include allopurinol, amiodarone, androgens (eg, danazol, methyltestosterone), anticonvulsants (eg, carbamazepine, phenobarbital, phenytoin), azole antifungals (eg, fluconazole, ketoconazole), beta-blockers, bosentan, bromocriptine, calcium channel blockers, colchicine, oral contraceptives, corticosteroids, fluoroquinolones (eg, ciprofloxacin), foscarnet, HMG-CoA reductase inhibitors, imipenem-cilastatin, macrolide antibiotics, methotrexate, metoclopramide, nafcillin, nefazodone, orlistat, potassium-sparing diuretics, probucol, rifamycins (rifampin, rifabutin), serotonin reuptake inhibitors (SSRIs eg, fluoxetine, sertraline),... 

Mechanism of Action A potassium-sparing diuretic that inhibits sodium, potassium, ATPase. Interferes with sodium and potassium exchange in distal tubule, cortical col-lectingtubule, and collecting duct. Increases sodium and decreases potassium excretion. Also increases magnesium, decreases calcium loss. TAerapeuticEffect Produces diuresis and lowers BP. 

Thiazide diuretics are ineffective once the GFR becomes less than 25 mL/min, and loop diuretics are often used at high doses (e.g. furosemide 500 mg to 1 g daily) to gain an effect. Metolazone is effective when combined with a loop diuretic. Potassium-sparing diuretics such as amiloride are not recommended. Spironolactone is not generally used, but is beneficial in low dose for the treatment of heart failure even in patients on dialysis. Beta-blockers and calcium channel blockers are generally well tolerated. Any ankle swelling with calcium channel blockers must not be confused with fluid overload. 

AMIODARONE POTASSIUM-SPARING DIURETICS Risk of T levels of eplerenone with amiodarone risk of hyperkalaemia directly related to serum levels Calcium channel blockers inhibit CYP3A4-mediated metabolism of eplerenone Restrict dose of eplerenone to 25mg/day. Monitor serum potassium concentrations closely watch for hyperkalaemia... 

Diuretics. Hypercalcaemia may develop in patients administered thiazide diuretics with either calcium or vitamin D supplements, leading to a need to monitor plasma or serum calcium levels. The concurrent use of potassium-sparing diuretics, and other potassium supplements or potassium-containing salt substitutes, could lead to serious hyperkalaemia. Hyperkalaemia is known to interfere with the absorption of vitamin B12. There is a need to warn patients and monitor serum potassium levels. The risk of hypokalaemia is minimal with low doses of thiazides, for example 5 mg of bendroflumethiazide. Hypokalaemia is a concern in patients receiving treatment with drugs such as digoxin, amiodarone, disopyramide or flecainide (drugs used to treat cardiac disorders). 

The manufacturers report that in population pharmacokinetic analysis, there was no effect on sildenafil pharmacokinetics in those taking ACE inhibitors, calcium-channel blockers and tMazide and related diuretics whereas the AUC of the less potent active metabolite of sildenafil is increased by 62% by loop and potassium-sparing diuretics and by 102% by non-selective beta blockers, although these changes were not considered clinically relevant. ... 

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