McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 5 1 Diuretic agents

should be used to monitor serum levels of individuals taking lithium. P otassium - sparing diuretics The potassium-sparing diuretics are not as powerful as the loop diuretics, but they retain potassium instead of wasting it. Drugs include amiloride ( Kaluril ), spironol- actone ( Aldactone ), eplerenone ( Inspra ) and triamterene ( Hydrene [not available in New Zealand]). These diu- retics are used for individuals who are at high risk for hypokalaemia associated with diuretic use (e.g. indi- viduals receiving digitalis or individuals with cardiac arrhythmias). Therapeutic actions and indications Potassium-sparing diuretics cause a loss of sodium while promoting the retention of potassium. Spironol- actone acts as an aldosterone antagonist, blocking the actions of aldosterone in the distal tubule. Amiloride and triamterene block potassium secretion through the tubule. The diuretic effect of these drugs comes from the balance achieved in losing sodium to offset the potas- sium retained. Potassium-sparing diuretics are often used as adjuncts with thiazide or loop diuretics or in people who are especially at risk if hypokalaemia develops, such as individuals taking certain antiarrhythmics or digoxin and those who have particular neurological conditions. Spironolactone, the most frequently prescribed of these drugs, is the drug of choice for treating hyperaldos- teronism , a condition seen in cirrhosis of the liver and nephrotic syndrome (see Table 51.2). should maintain your usual fluid intake and try to avoid excessive intake of salt. • Frusemide is a diuretic that causes potassium loss, so you should eat foods that are high in potassium (e.g. orange juice, raisins, bananas). • Weigh yourself each day, at the same time of day and in the same clothing. Record these weights on a calendar. Report any loss or gain of 2 kg or more in 1 day. • Common effects of this drug include the following: • Increased volume and frequency of urination : Have ready access to bathroom facilities. Once you are used to the drug, you will know how long the effects last for you. • Dizziness, feeling faint on rising, drowsiness : Loss of fluid can lower blood pressure and cause these feelings. Change positions slowly; if you feel drowsy, avoid driving or other dangerous activities. These feelings are often increased if alcohol is consumed; avoid this

Pharmacokinetics These drugs are well absorbed after oral administra- tion, are protein bound and widely distributed. They are metabolised in the liver and primarily excreted in urine. These diuretics cross the placenta and enter breast milk. Spironolactone has a slow onset of action, 24 to 48 hours, reaches peak effects in 48 to 72 hours and has a duration of effect of 72 hours. Amiloride and tri- amterene reach peak effects in 6 to 10 hours and have a duration effect of 16 to 24 hours. Contraindications and cautions These drugs are contraindicated for use in individu- als with allergy to the drug to prevent hypersensitivity reactions , and hyperkalaemia, renal disease or anuria, which could be exacerbated by the effects of these drugs. Routine use during pregnancy is not appropriate; these drugs should be reserved for situations in which the mother has pathological reasons for use, not pregnancy manifestations or complications, and only if the benefit to the mother clearly outweighs the risk to the fetus. Adverse effects The most common adverse effect of potassium-sparing diuretics is hyperkalaemia, which can cause lethargy, confusion, ataxia, muscle cramps and cardiac arrhyth- mias. People taking these drugs need to be evaluated regularly for signs of increased potassium and informed about the signs and symptoms to watch for. They also should be advised to avoid foods that are high in potas- sium (Box 51.2). Because these drugs work much like aldosterone, they are associated with various androgen (another similar hormone) effects such as hirsutism, combination or take special precautions if you combine them. • Increased thirst : As fluid is lost, you may experience a feeling of thirst. Sucking on sugarless lozenges and frequent mouth care might help to alleviate this feeling. Do not drink an excessive amount of fluid while taking a diuretic. Try to maintain your usual fluid intake. • Report any of the following to your healthcare provider: muscle cramps or pain, loss or gain of more than 2 kg in 1 day, swelling in your fingers or ankles, nausea or vomiting, unusual bleeding or bruising, trembling or weakness. • Avoid the use of any over-the-counter (OTC) medication without first checking with your healthcare provider. Several OTC medications can interfere with the effectiveness of this drug. • Tell any doctor, nurse or other healthcare provider involved in your care that you are taking this drug. • Keep this drug, and all medications, out of the reach of children.