Pharmacology, part 41: Renal Medications - Diuretics

by Cathy Parkes September 15, 2021 Updated: March 13, 2022 9 min read

This article focuses on diuretics and some of the most important diuretic medications you need to know.

The Nursing Pharmacology video series follows along with our Pharmacology Second Edition Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.

Cool Chicken When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!

What is a diuretic?

Diuretics, also known as water pills, may be administered to reduce a patient’s blood pressure. Diuretics work by helping rid the body of salt (sodium) and water. When administered, these medicines help the kidneys increase the amount of sodium in a patient’s urine, which in turn helps remove water from the blood, decreasing the amount of fluid flowing through the patient’s veins and arteries — thus reducing the patient’s blood pressure.

Loop diuretic - furosemide (Lasix)

Cool Chicken Furosemide furiously gets rid of excess sodium and water.

The key loop diuretic medication that falls within this class is furosemide, known by its brand name, Lasix. This is a very important medication to know, as it gets administered regularly in the hospital.

Furosemide is used to treat conditions such as pulmonary edema (swelling caused by excess fluid trapped in the body’s tissues); edema related to heart failure, liver disease, and kidney disease; and hypertension.

Furosemide mode of action

Furosemide works by blocking the reabsorption of sodium, chloride, and water at the ascending loop of Henle (part of a kidney tubule that forms a long loop in the medulla of the kidney, from which water and salts are reabsorbed into the blood).

It also causes increased excretion of potassium, magnesium, and calcium, which causes rapid diuresis (excess urination).

Furosemide side effects

Furosemide’s fast action — ridding the body of so much fluid so quickly — places the patient at risk for hypotension (low blood pressure) and dehydration.

Other side effects include key electrolyte imbalances like hyponatremia and hypokalemia, because furosemide efficiently rids the body of electrolytes, too. Whenever there is an imbalance of potassium, whether due to hyperkalemia or hypokalemia, it can place the patient at risk for life-threatening dysrhythmias. That means it’s important to monitor the patient’s potassium levels, as well as other electrolytes.

Furosemide can cause ototoxicity (balance or hearing issues). Make sure to assess the patient and ask them if they have experienced any hearing loss or if they have tinnitus or other symptoms of ototoxicity.

Additional side effects of furosemide include hyperglycemia, and rash.

Furosemide nursing care

Administer furosemide prior to 5:00 p.m., because this medication will cause the patient to urinate, and the need to pee more frequently can cause sleep disruptions. Administering the medication earlier in the day should help prevent sleep-interrupting trips to the toilet at night.

Administer furosemide slowly, infusing at 20 mg/min.

Monitor the patient's weight daily, monitor their Is and Os, and (as noted above) monitor their electrolyte levels.

Patient teaching when administering furosemide

Encourage the patient to increase their intake of potassium-rich foods because of the risk of hypokalemia. Foods that are high in potassium include bananas, dark leafy greens, potatoes, cantaloupe, avocado, and tomatoes.

Thiazide diuretic - hydrochlorothiazide (Microzide)

Cool Chicken Hydrochlorothiazide gets rid of water (“hydro”) and NaCl (sodium chloride).

Hydrochlorothiazide is a thiazide diuretic (a medication recommended for high blood pressure). It is used to treat conditions such as hypertension, often in conjunction with other antihypertensive medications.

Hydrochlorothiazide is also used to treat edema (swelling) related to heart failure, liver disease, or kidney disease.

Hydrochlorothiazide mode of action

The mode of action of hydrochlorothiazide is to block the reabsorption of sodium chloride and water at the distal convoluted tubule. It also causes increased excretion of other electrolytes (similar to furosemide), so it will cause increased excretion of potassium, calcium, and magnesium.

Hydrochlorothiazide side effects

Among the key side effects of hydrochlorothiazide are dehydration, as well as hypokalemia and hyponatremia, both as a result of eliminating electrolytes.

Hydrochlorothiazide nursing care

Nursing care when administering hydrochlorothiazide is the same as for furosemide:

  • Administer during the day if possible (so the patient doesn't interrupt a night's sleep because they have to urinate frequently)
  • Weigh the patient daily
  • Monitor their Is and Os
  • Monitor their electrolyte levels

Patient teaching when administering hydrochlorothiazide

As with furosemide, encourage the patient to consume foods high in potassium, because of the key side effect of hypokalemia.

Potassium-sparing diuretic - spironolactone (Aldactone)

Cool Chicken Spironolactone will improve your spirits because you won’t lack potassium!

Spironolactone is a potassium-sparing diuretic, increasing diuresis without the loss of potassium. Potassium-sparing diuretics are often prescribed in combination with other types of diuretics.

Spironolactone can be prescribed for heart failure and hypertension. It is contraindicated in patients who have severe kidney failure.

Spironolactone mode of action

Spironolactone works by blocking aldosterone, which promotes the excretion of sodium and water, but retains potassium.

Spironolactone side effects

Side effects of spironolactone include hyperkalemia (due to the retention of potassium).

Other side effects include amenorrhea (lack of menstruation), gynecomastia (an increase in the amount of breast gland tissue in boys or men), and impotence.

Black box warning for spironolactone

Spironolactone has a black box warning due to the possibility that it could increase the size of certain tumors and increase the risk for breast, uterus, ovary, and cervical cancers.

Spironolactone nursing care

Monitor the patient's potassium levels during therapy because of the risk for hyperkalemia.

Patient teaching when administering spironolactone

It is also important to teach the patient to avoid salt substitutes, because salt substitutes are high in potassium.

Osmotic diuretic - mannitol (Osmitrol)

Cool Chicken I had a headache (due to increased ICP). I took mannitol, and “man, it all went away”.

Osmotic diuretics are used to treat edema, as well as to lower intraocular pressure (IOP) in glaucoma and before ophthalmologic procedures. They are also used to lower intracranial pressure (ICP), such as following head trauma. Mannitol is a frequently prescribed osmotic diuretic.

Mannitol mode of action

Mannitol works by increasing the serum osmolality, which draws fluid from the intracellular space into the interstitial space, as well as into the plasma or the bloodstream. This helps reduce ICP and IOP.

Mannitol side effects

Side effects of mannitol can include pulmonary edema as well as heart failure, due to the volume of fluid drawn back into the bloodstream.

Other side effects include renal failure, dehydration, and electrolyte imbalances (particularly sodium and potassium), as well as the possibility of phlebitis.

Mannitol nursing care

It is also important to ensure the patient’s intracranial pressure or intraocular pressure fall back into their expected ranges:

  • For ICP, the expected range is between 10 and 15 mmHg
  • For IOP, the expected range is between 10 and 21 mmHg

Our Lab Values Study Guide & Flashcard Index is a list of lab values covered in our Lab Values Flashcards for nursing students and can be used as an easy reference guide.

Patient teaching when administering mannitol

Mannitol should be given slowly; it's possible the patient receives the medication around the clock.

Patients should alert their caregivers if they feel any burning, pain, or swelling around the IV needle when mannitol is injected.

Patients will also require frequent medical tests to be sure this medicine is not causing harmful effects.


Full Transcript

All right. In this video, we are going to talk about diuretics, and we're going to start off by talking about loop diuretics.

The key medication that falls within this class is furosemide or brand name, Lasix. This is a very important medication to know. You will administer it all the time in the hospital. In addition, chances are you're probably going to get questions about furosemide on your nursing exams.

So furosemide is used to treat conditions such as pulmonary edema, edema related to heart failure, liver disease, as well as kidney disease. In addition, it can be used for hypertension.

It works by blocking the reabsorption of sodium, chloride, and water at the ascending loop of Henle. It also causes increased excretion of potassium, magnesium, and calcium as well. So it does all of these things pretty quickly. It causes rapid dieresis.

So some of the side effects you can kind of guess based on the mode of action. Because we're getting rid of all of this fluid very, very quickly, it places the patient at risk for hypotension as well as dehydration, and because we're getting rid of all of these electrolytes as well, it places the patient at risk for key electrolyte imbalances, which include hyponatremia as well as hypokalemia. And any time we have an imbalance with potassium, whether that's hyperkalemia or hypokalemia, it places the patient at risk for life-threatening dysrhythmias. So we're definitely going to want to keep an eye on their potassium levels, as well as the other electrolytes when a patient is on furosemide.

Other side effects include autotoxicity. So you definitely want to assess your patient and ask them if they have had any hearing loss or if they have any tinnitus or other symptoms of autotoxicity. Other side effects include hyperglycemia, as well as a rash.

In terms of key teaching points, if we can administer this medication prior to 5:00 PM, we want to do so, because administering furosemide is going to cause the patient to pee a lot, and we don't really want to keep them up all night peeing. So if we can give it to them during the day, that's definitely going to be better. We're going to administer furosemide slowly, so we're not going to just slam it into the patient. We're going to give it at a rate of 20 milligrams per minute. We're going to weigh our patients daily, monitor their Is and Os, and also monitor their electrolyte levels, which is very important.

And then we want to encourage our patient to increase their intake of potassium-rich foods because of the risk of hypokalemia. So foods that are high in potassium include dark leafy greens, potatoes, cantaloupe, tomatoes, avocado, as well as other foods.

And then the way I remember this medication is if you look at the word furosemide, it starts with that F-U-R. And I remember that furosemide furiously gets rid of excess water.

All right. Now let's talk about thiazide diuretics. So the medication that falls within this class to know is hydrochlorothiazide.

Hydrochlorothiazide is used to treat conditions such as hypertension, often in conjunction with other antihypertensive medications. It's also used to treat edema related to heart failure, liver disease, or kidney disease.

The mode of action of hydrochlorothiazide is to block the reabsorption of sodium chloride and water at the distal convoluted tubule. It also causes increased excretion of other electrolytes just like furosemide, so it will cause increased excretion of potassium, calcium, as well as magnesium.

So in terms of side effects, key side effects include dehydration, because again, any time we have a diuretic, that's going to be a key risk factor. Also, hypokalemia is a key side effect, as well as hyponatremia because we're getting rid of those electrolytes.

So some of the key points in teaching are going to be the same as what we saw with furosemide. So we're going to want to administer this diuretic during the day if possible so that the patient isn't up all night peeing. We're going to want to weigh the patient daily, monitor their Is and Os, and monitor their electrolyte levels. And then we're going to want to encourage them to consume foods that are high in potassium because of that key side effect of hypokalemia. So we talked about those foods when we were talking about furosemide, so you just want to provide that education to your patient.

In terms of my little trick for remembering this medication, if you look at the word hydrochlorothiazide, it contains the word hydro for water and chloro, which is part of sodium chloride. So hydrochlorothiazide gets rid of water, hydro, and sodium chloride.

All right. Let's now talk about a potassium-sparing diuretic, which is spironolactone.

Spironolactone can be used for heart failure, as well as hypertension. It is contraindicated in patients who have severe kidney failure.

Its mode of action is to block aldosterone, which promotes the excretion of sodium and water, but the retention of potassium.

So key side effects include hyperkalemia because we are retaining that potassium. Other side effects include amenorrhea, which is lack of menstruation, as well as gynecomastia and impotence.

In terms of key administration points, you want to monitor your patient's potassium levels during therapy because of the risk for hyperkalemia, and you want to tell your patient to avoid salt substitutes because salt substitutes are high in potassium.

The way I remember this medication, if you look at how it's spelled, it's spelled S-P-I-R, so I think spironolactone will improve your spirits because you won't lack potassium. And that helps me to remember that this medication allows for retention of potassium.


All right. So let's finally talk about an osmotic diuretic, which is mannitol.

So mannitol is used for edema, as well as increased intracranial pressure. It's also used for increased intraocular pressure.

It works by increasing the serum, osmolality, which draws fluid from the intracellular space into the interstitial space, as well as into the plasma or the bloodstream.

So side effects of this medication can include pulmonary edema as well as heart failure. Because we're bringing all of this fluid back into the bloodstream, it can really overwhelm the lungs and the heart. Other side effects include renal failure, dehydration, as well as electrolyte imbalances, particularly with sodium and potassium, and then possible phlebitis.

In terms of key administration points, we're going to want to monitor our patient's weight, monitor their Is and Os, as well as their electrolyte levels. We also want to make sure we're bringing their intracranial pressure or intraocular pressure back into the expected range.

So the expected range for ICP is between 10 and 15 mmHg, and the expected range for IOP is between 10 and 21 mmHg.

The way I remember this medication is that I had a headache due to increased ICP. I took mannitol, and man, it all went away. So hopefully that's helpful for you.

We will be back with key medications for the reproductive system. Thanks so much for watching.


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