34.2: Loop Diuretics

Learning Objectives

By the end of this section, you should be able to:

• 34.2.1 Identify the characteristics of loop diuretic drugs used for fluid volume excess and renal system disorders.
• 34.2.2 Explain the indications, actions, adverse reactions, and interactions of loop diuretic drugs used for fluid volume excess and renal system disorders.
• 34.2.3 Describe nursing implications of loop diuretic drugs used for fluid volume excess and renal system disorders.
• 34.2.4 Explain the client education related to loop diuretic drugs used for fluid volume excess and renal system disorders.

Loop diuretics are the most frequently prescribed type of diuretic drug. They are used to treat fluid volume excess and edema associated with heart failure, hypertension, cirrhosis, and renal disease. Loop diuretics act at different points in the nephron to increase sodium and water losses.

Introduction and Use

Loop diuretics increase urinary output by blocking the reabsorption of sodium in the (thick) ascending loop of Henle. The drugs work by inhibiting the action of the sodium–potassium–chloride (Na-K-2Cl or NKCC2) cotransporters in the luminal membrane and increasing water excretion. Blocking the NKCC2 cotransporter blocks potassium reabsorption and triggers calcium and magnesium losses. Loop diuretics are commonly recommended for treating edematous conditions and fluid volume excess associated with heart failure and renal disease. They are approved for treating hypertension but are usually prescribed in combination with other antihypertensives (Huxel et al., 2023). The most frequently used loop diuretics, furosemide, torsemide, and bumetanide, are recommended for treating specific conditions according to their half-life and bioavailability characteristics.

Furosemide, a frequently prescribed loop diuretic, treats edematous conditions and fluid volume excess in heart failure, liver failure, and acute and chronic renal disease, including nephrotic syndrome (Khan et al., 2023). It can be given orally, subcutaneously, intramuscularly, or intravenously. The bioavailability of oral doses of furosemide is approximately 50%, and the drug has a shorter half-life (1.5–2 hours) than other loop diuretics, which means that a continuous intravenous infusion may be more effective than intermittent doses in critically ill clients (Khan et al., 2023). Furoscix was approved in 2022 for subcutaneous delivery of a daily metered dose of furosemide by an on-body infuser for outpatient clients with New York Heart Association class II or III chronic heart failure (Dahiya et al., 2022).This delivery system is intended for clients in the home setting for whom oral furosemide administration has limited effectiveness.

Torsemide exhibits a stronger diuretic effect than furosemide does (Yifan et al., 2021). The drug is used to treat heart failure, hepatic cirrhosis, and chronic renal disease, and it is used with other antihypertensive drugs to treat hypertension (Kanderi & Vaitla, 2023). It can be administered orally or intravenously. The bioavailability of torsemide given by mouth or intravenously is 80%, and the duration of action is 6–8 hours (Kanderi & Vaitla, 2023).

Bumetanide is used to treat clients who do not respond to other loop diuretics, have severe renal disease, or require larger diuretic doses (Sidhu & Puckett, 2023). It is used to manage heart failure, hypertension, hypercalcemia, oliguria, and ascites associated with liver failure, and it may also replace furosemide in clients with additional risk factors for ototoxicity. The drug can be administered orally, intramuscularly, or intravenously.

Table 34.2 lists common loop diuretics and typical routes and dosing for adult clients.

Table 34.2 Drug Emphasis Table: Loop Diuretics (source: https://dailymed.nlm.nih.gov/dailymed/)

Drug	Routes and Dosage Ranges
Furosemide (Lasix, Furoscix)	Edema due to congestive heart failure, liver cirrhosis, renal disease, or nephrotic syndrome: 20–80 mg orally daily; maximum daily dose: 600 mg. 20–40 mg intravenously (IV) or intramuscularly, may be repeated in 2 hours. Hypertension: 80 mg orally, usually divided into doses of 40 mg twice daily. Acute pulmonary edema: 40 mg IV, may be repeated in an hour. Congestive heart failure: Subcutaneous administration of Furoscix, 30 mg for the first hour; 12.5 mg/hour for the next 4 hours.
Torsemide (Demadex)	Congestive heart failure: Initial dose: 10–20 mg orally or IV once daily. Double the dose as needed until the desired diuretic effect is attained, not to exceed 200 mg. Chronic renal failure: Initial dose: 20 mg orally or IV once daily. Double the dose as needed until the desired diuretic effect is attained, not to exceed 200 mg. Hepatic cirrhosis: 5–10 mg orally or IV once daily, administered with an aldosterone agonist or potassium-sparing diuretic. Double the dose as needed until the desired diuretic response is attained, not to exceed 40 mg. Hypertension: 5 mg orally once daily. If needed after 4–6 weeks, double the dose. If 10 mg is not sufficient, add an additional antihypertensive agent.
Bumetanide (Bumex)	0.5–2 mg orally once daily, initially; may repeat a second or third dose every 4–5 hours as needed until the desired diuretic effect is attained; usual dose: 0.5–2 mg/day; maximum dose: 10 mg/day. 0.5–1 mg IV or intramuscularly once, initially; may repeat a second or third dose every 2–3 hours as needed until the desired diuretic effect is attained; maximum dose: 10 mg/day.

Adverse Effects and Contraindications

Loop diuretics primarily cause diuresis-induced electrolyte imbalances (Huxel et al., 2023). These alterations are more common in older adults and clients with inadequate fluid intake. Other common adverse effects include headache, dizziness, and postural hypotension. Metabolic effects may include hyperlipidemia, metabolic alkalosis, and hyperglycemia due to impaired glucose tolerance. Drug-induced pancreatitis also has been reported, most often in clients with a history of pancreatitis. Less common reactions include impotence, thrombocytopenia due to the secretion of antibodies, thrombotic events related to hypovolemia, and ototoxicity due to rapid intravenous administration.

Loop diuretics should be used with care in older adults and clients with cardiovascular disease, diabetes, and other risk factors for fluid volume and electrolyte alterations, such as dehydration and increased glucose tolerance. Clients who are allergic to sulfa may possibly experience a mild reaction when using loop diuretics.

Severe dehydration or anuria is a contraindication to any diuretic (Arumugham & Shahin, 2023). Loop diuretics are contraindicated in clients with sensitivity to one of the individual drugs (furosemide, torsemide, or bumetanide) and in clients with Stevens–Johnson syndrome due to the probability of a sensitivity reaction.

Table 34.3 is a drug prototype table for loop diuretics featuring furosemide. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Table 34.3 Drug Prototype Table: Furosemide (source: https://dailymed.nlm.nih.gov/dailymed/)

Drug Class Loop diuretic Mechanism of Action Inhibits the reabsorption of sodium and water in the ascending loop of Henle, which increases urinary output	Drug Dosage Edema due to congestive heart failure, liver cirrhosis, renal disease, or nephrotic syndrome: 20–80 mg orally daily; maximum daily dose: 600 mg. 20–40 mg IV or intramuscularly, may be repeated in 2 hours. Hypertension: 80 mg orally, usually divided into 40 mg twice daily. Acute pulmonary edema: 40 mg IV, may be repeated in an hour. Congestive heart failure: Subcutaneous administration of Furoscix, 30 mg for the first hour; 12.5 mg/hour for the next 4 hours.
Indications Hypertension Pulmonary edema Peripheral edema Congestive heart failure Therapeutic Effects Lowers blood pressure Decreases edema	Drug Interactions ACE inhibitors Metformin Cisapride Diethylpropion Digoxin Dofetilide Ephedrine Lithium Methotrexate Phenytoin Cidofovir Food Interactions Foods with high salt content Alcohol Black licorice
Adverse Effects Hypokalemia Hyponatremia Orthostatic hypotension Hypovolemia Hyperglycemia Pancreatitis Azotemia Oliguria Thromboembolism Ototoxicity Agranulocytosis Hyperuricemia	Contraindications Anuria Stevens–Johnson syndrome Caution: Renal impairment Older adults Diabetes Hypersensitivity reaction to sulfa or any loop diuretic

Special Considerations

Use of Diuretics in Older Adults

Research indicates that older adults have an increased risk of falling associated with diuretic use. Various adverse effects associated with diuretic use contribute to fall risk, including orthostatic hypotension, increased urine output causing more frequent trips to the bathroom, increased risk of fluid and electrolyte disorders leading to cognitive changes, and effects on bone mass and muscle strength.

(Source: Bai et al., 2023)

Safety Alert

Loop Diuretics

Clients taking both furosemide and digoxin must be monitored for signs of digoxin toxicity, including bradycardia, nausea, vomiting, visual changes (halos), and cardiac arrhythmias. Clients taking loop diuretics as well as lithium must be monitored for toxic blood levels of lithium carbonate, which can develop because diuretics inhibit the kidneys’ excretion of the drug.

(Sources: DailyMed, Furosemide tablet, 2012; Huxel et al., 2023)

Nursing Implications

The nurse should do the following for clients who are taking loop diuretics:

• Monitor the client for adverse effects related to diuresis.
• Assess the client’s blood pressure and heart rate before the initial dose and then intermittently during drug therapy on an ongoing basis to monitor for orthostatic hypotension.
• Assess the client for signs of dehydration, including dry mucous membranes, poor skin turgor, and increased thirst.
• Monitor laboratory results for electrolyte imbalances and signs of renal dysfunction.
• Monitor urine output to evaluate the medication’s effectiveness.
• Assess the client’s body weight at baseline and on an ongoing basis to monitor fluid retention.
• Assess the client’s extremities and dependent areas for edema.
• Assess the client for adverse effects, drug and food interactions, and contraindications.
• Assess the client’s understanding of the disease process and the treatment plan, including medication administration, dietary restrictions, and when to call the health care provider.
• Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.

Clinical Tip

Intravenous Administration of Furosemide

Furosemide can be administered intravenously as a bolus injection or as a continuous or intermittent infusion for larger doses. A bolus dose should be administered slowly over 1–2 minutes. Rapid infusion rates of loop diuretics may trigger temporary or permanent hearing loss in susceptible clients.

(Source: DailyMed, Furosemide injection, 2022)

Trending Today

Furoscix Subcutaneous Drug Delivery System

A client-administered loop diuretic dosing system was approved in 2022 for the treatment of heart failure. The clinical trial investigators found the client outcomes and pharmacologic features of subcutaneous administration of Furoscix to be equal to those for intravenous administration of furosemide. Watch this brief video demonstration of its application and use.

(Source: Dahiya et al., 2022)

Client Teaching Guidelines

The client taking a loop diuretic should:

• Follow a modified sodium diet with moderate intake of potassium-rich foods to counteract potassium losses.
• Avoid potential food interactions, including black licorice and alcohol.
• Maintain the prescribed fluid intake to avoid dehydration.
• Monitor for and report any skin changes.
• Change position slowly when going from a lying or sitting position to standing to avoid orthostatic hypotension.
• Notify their health care provider if they experience headaches or dizziness.

The client taking a loop diuretic should not:

• Self-adjust a dose without consulting their health care provider.
• Take this medication at night; daytime administration will avoid nocturnal urinary frequency caused by the diuretic effect of the medication.
• Drive or operate machinery if experiencing dizziness.

FDA Black Box Warning

Loop Diuretics

Loop diuretics can cause severe water loss and electrolyte imbalance when administered at higher dosages.