Diuretics - Thiazide, thiazide-like, loop, and potassium-sparing diuretics: Nursing pharmacology

Diuretics, also called water pills, are medications that act on the kidneys to increase diuresis, or the production of urine, to help excrete more water from the body.

Therefore, they are generally used to treat hypertension, as well as edema caused by fluid overload conditions, such as heart failure and pulmonary edema, as well as renal diseases like nephrotic syndrome and hepatic diseases like cirrhosis.

Diuretics are most often administered orally, but some of them can also be administered intravenously. Once administered, these diuretics act on the kidney's basic unit, the nephron, to induce electrolyte and water excretion.

Zooming into the nephron, it's made up of a glomerulus, which filters the blood. The filtered content goes through the renal tubules, which have four parts, the proximal convoluted tubule, the U-shaped loop of Henley, with a thin descending, a thin ascending, and a thick ascending limb, the distal convoluted tubule, and the collecting duct, which drain the urine out of the kidneys.

Now, the main classes of diuretics include thiazide and thiazide-like diuretics, loop diuretics, and potassium-sparing diuretics.

OK, starting with thiazide diuretics and thiazide-like diuretics, which have a slightly different structure but act in the same way.

Available thiazide diuretics include chlorothiazide and hydrochlorothiazide, while examples of thiazide-like diuretics are chlorthalidone and indapamide.

Now, once administered, thiazide and thiazide-like diuretics act on the distal convoluted tubule, which has a sodium chloride transporter that reabsorbs one sodium and one chloride ion together from the tubule.

Thiazide diuretics block this transporter, which inhibits the reabsorption of sodium and chloride ions. And since water follows sodium, there will be more water molecules in the lumen as well, so more urine is produced.

Now, thiazide and thiazide-like diuretics are the first-line treatment of hypertension. However, these medications can't induce immediate or large volume diuresis.

For this reason, they're not typically used alone for fluid overload conditions, such as heart failure and pulmonary edema.

Now, as with any type of diuretic, side effects of thiazide and thiazide-like diuretics mainly manifest as dehydration and electrolytes imbalance.

First off, thiazide diuretics tend to cause more retention of calcium and uric acid, which can result in hypercalcemia and hyperuricemia.

Thiazides can also cause hypomagnesemia, hypochloremia, hyponatremia, as well as hypokalemia, which can cause arrhythmia, muscle cramps and weakness.

And due to the increased excretion of these electrolytes, thiazides may lead to metabolic alkalosis. Finally, thiazides can tamper with the metabolism of glucose and fat, which may lead to hyperglycemia, hyperlipidemia, and an increase in serum cholesterol and LDL.

As far as the contraindications go, thiazide diuretics should be avoided in clients with conditions like gout, diabetes mellitus, and hyperlipidemia.

Thiazides are also contraindicated in clients who have renal failure with uria. Finally, thiazides are sulfa medications, so they're contraindicated in clients with sulfa allergy.

Next, we have loop diuretics, such as furosemide, torsemide, bumetanide, and ethecrinic acid. As the name suggests, loop diuretics act on the loop of Henley.

To be more specific, they mainly target the thick ascending limb, which has sodium, potassium chloride co-transporters that normally reabsorb 30% of the filtered sodium, potassium, and chloride.

Now, loop diuretics block these transporters, so these ions end up being excreted, and water follows them passively later across the collecting duct.

Because loop diuretics cause the excretion of a large amount of the filtered sodium in urine, their diuretic effect is almost 3 times greater than thiazide diuretics.

For this reason, loop diuretics are typically used to treat conditions that need a rapid and large diuresis, such as heart failure and pulmonary edema.

Now, in terms of side effects, loop diuretics can also cause dehydration and electrolyte imbalance, such as hypocalcemia and hypomagnesemia, as well as hypochloremia, hyponatremia, and hypokalemia.

And due to the increased excretion of these electrolytes, loop diuretics may lead to metabolic alkalosis. Other side effects are hypotension due to their strong diuretic effect, as well as ootoxicity, which can result in hearing impairment and tinnitus, especially when combined with other ootoxic medications like aminoglycosides.

Finally, loop diuretics can tamper with the metabolism of glucose, which may lead to hyperglycemia. Loop diuretics should not be given to clients who already present with electrolyte imbalance, severe renal failure with uria, as well as in hepatic encephalopathy, which could be exacerbated by dehydration.

In addition, loop diuretics should be avoided in clients with sulfa allergy, and should not be combined with other ootoxic medications.

Finally, loop diuretics should be used with caution in clients with diabetes mellitus. All right, moving on to potassium-sparing diuretics, which act on the distal convoluted tubules and the collecting tubules.

These tubules have ATP dependent potassium pumps that secrete potassium into the lumen to be excreted in urine, as well as hydrogen pumps that secrete hydrogen into the urine, and epithelial sodium channel pumps, or ENACs, which reabsorb sodium.

Now, the secretion and reabsorption of these ions in the distal convoluted and collecting tubules are regulated by the mineralocorticoid hormone, aldosterone, which induces the synthesis of these pumps.

Now, there are 2 types of potassium-sparing diuretics according to their mechanism of action. On the one hand, we've got those that directly inhibit the aldosterone receptor, like spironolactone and plainone.

These medications can also be used to treat hyperaldosteronism, a condition where the adrenal gland produces excess aldosterone.

On the other hand, we have medications that block the ENAC pumps like amylori and triamterene. Ultimately, both have the same effect, so they increase the excretion of sodium, which is followed by water, resulting in diuresis.

But at the same time, they decrease the excretion of potassium, as well as hydrogen, hence the name potassium sparing. Now, potassium-sparing diuretics are pretty weak, so they're typically combined with other diuretics like thiazides or loop diuretics.

As a result, potassium-sparing diuretics can help prevent hypokalemia. Now, an important side effect of potassium-sparing diuretics is hyperkalemia.

In addition, these medications also increase hydrogen retention, which may lead to metabolic acidosis. Very rarely, spironolactone may cause anti-androgenic side effects.

In males, this may result in gynecomastia and impotence, while females may present with hirsutism and menstrual irregularities.

On the other hand, for triamterene, the main side effect is kidney stones. Potassium-sparing diuretics should be avoided in clients with renal failure with anuria, severe hepatic disease, or with hyperkalemia.

Caution should be taken in clients who take other medications that elevate blood levels of potassium level, such as angiotensin converting enzyme or ACE inhibitors.

OK, before administering a diuretic, first perform a baseline assessment that includes weight, vital signs, and fluid balance, including assessment of skin tergur and mucous membranes.

If your client has edema, assess the location and extent of the edema. If your client has heart failure or pulmonary edema, assess their respiratory status and auscultate their lung sounds.

And if your client has ascites, measure their abdominal girth. Lastly, review recent laboratory results, including electrolytes, especially sodium, potassium, calcium, and chloride, as well as glucose, uric acid, renal and hepatic function, and lipid profile.

Now, if your client with pulmonary edema is prescribed intravenous loop diuretic like furimoside, teach them how the medication will help them breathe more easily.

Remember to administer it slowly over 1 to 2 minutes, or by continuous infusion for higher doses. During treatment, continue to monitor their breath sounds and respiratory status.

Weigh your client daily, measure their urine output, and watch for signs of dehydration. Also be sure to keep a close eye on their renal function and serum electrolytes, especially potassium, and monitor for signs of hypokalemia, such as muscle cramps or heart palpitations, particularly if your client is also taking digoxin.

If your client is diagnosed with diabetes, regularly monitor their blood glucose levels. Lastly, teach your client to let you know right away if they experience symptoms of autotoxicity, such as ringing in the ears, decreased hearing, or dizziness.

When your client with hypertension is prescribed a thiazide diuretic like hydrochlorothiazide, teach them how the medication helps reduce their BP.

Then explain how initially they could feel lightheaded when rising from a lying or sitting position, and advise them to make position changes slowly until they adjust to the medication.

Let them know they can take their medication with or without food. In addition, explain that diuretics may cause them to urinate more frequently, and instruct them to take their medication early in the day to avoid interruption of their sleep from nocturia.

Advise them to weigh themselves daily and to notify their healthcare provider for significant changes in their weight. Explain that their medication can decrease their potassium levels in their blood, and instruct them to report signs of hypokalemia, such as muscle cramps or heart palpitations.

To prevent this, encourage your client to include foods that contain potassium in their diet, like bananas, cantaloupe, and potatoes.

Next, teach them how to monitor their own BP at home and encourage them to continue their prescribed regimen of diet, exercise, and weight reduction as needed.

Also let them know that follow-up appointments and routine laboratory tests will be needed during therapy. OK, lastly, if your client is prescribed a potassium-sparing diuretic like spironolactone, let them know they can take their medication with or without food.

But be sure to teach them about the possibility of hyperkalemia. Stress the importance of avoiding high potassium foods and salt substitutes, and instruct them to immediately report symptoms of hyperkalemia, such as nausea, vomiting, muscle twitching or cramps, trouble breathing or heart palpitations.

As with other diuretics, instruct your client to take their medication early in the day to avoid nocturia. Finally, instruct your client to report symptoms of endocrine problems such as menstrual irregularities, gynecomastia, or impotence.

Alright, as a quick recap, diuretics are medications that act on the kidneys to help excrete more water from the body. They're used to treat conditions like hypertension, fluid overload from heart failure and pulmonary edema, as well as diseases like nephrotic syndrome and cirrhosis.

Thiazide and thiazide-like diuretics act on the distal convoluted tubule of the kidney to inhibit reabsorption of sodium and chloride ions.

On the other hand, loop diuretics act on the loop of Henley to increase the excretion of sodium, potassium, and chloride.

Finally, potassium-sparing diuretics act on the distal convoluted tubules and collecting tubules to increase the excretion of sodium while decreasing the excretion of potassium.

Nursing considerations include performing a baseline assessment, monitoring for changes in fluid and electrolyte balance, and evaluating the effectiveness of therapy.

Finally, client teaching is focused on safe self-administration, dietary modifications, and monitoring for side effects.