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Hydrochlorothiazide (HCTZ) – Thiazide Diuretics (Nursing)

by Rhonda Lawes

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    00:00 Let's take a look at one of the most commonly prescribed thiazide diuretics, hydrochlorothiazide.

    00:09 I have to say that slowly because it is a tongue twister for me which is why you often see it abbreviated as HCTZ. Now, let's talk about how hydrochlorothiazide works. It's the most commonly prescribed one, it blocks the reabsorption of sodium and chloride in the early distal convoluted tubule. Now, if I'm studying for a pharmacology exam, you don't necessarily have to remember that it's early in the distal convoluted tubule. We just put that on there as a frame of reference for you. This is also considered a type of loop diuretic. Remember it's not as strong as furosemide.

    00:45 Most diuretics like, you know, all of them blocks some type of electrolyte. Right? That's why we tell the body not to reabsorb the electrolyte because water will follow it which is our goal. So, mechanisms of actions will sound kind of similar to you. They're harder on certain electrolytes than others but that's the common denominator when it comes to the mechanism of action of diuretics.

    01:08 They are going to tell the body to get rid of these electrolytes and water follows. Now the difference with hydrochlorothiazide is because it's a thiazide diuretic, the GFR, the glomerulofiltration rate of your kidney needs to be greater than 15-20 mL/min so the GFR needs to be greater than 15-20 mL/min in order for this drug to work. So, this is not the drug that we would use if your patient is in renal failure and I keep stressing that because that's a really important concept for you to understand in pharmacology. Furosemide or other loop diuretics are what we would use for patient who's in renal failure. Hydrochlorothiazide is a mild diuretic that we use for people, we just want to lower their blood pressure a little or pull off a little extra fluid. We just can't use it as an effective medication for people whose kidneys are really struggling. Let's talk about what it feels like as a patient to take hydrochlorothiazide. Well, once you take a tablet you'll notice in about 2 hours an increase need to go to the bathroom and that could last for up to 12 hours. So as a nurse, what do you think about the timing of this medication? Well hopefully what's registering to you is that you should educate your patient "take this pill in the morning" because if they take it at nighttime they're going to be up and down, up and down all night long having to go to the bathroom. So it will take about 2 hours to kick in, after that it will last for up to 12 hours so make sure your patient knows to take this first thing in the morning. Now for this patient, we're likely treating essential hypertension, meaning it's just a little bit high.

    02:49 If we pull off some fluid, we should bring down their blood pressure or some mild edema but not for patients in renal failure. Let's look at the adverse effects of hydrochlorothiazide. The kind of cool thing is they're similar to furosemide. So if you've already studied that medication, you've got some of these down. Now ototoxicity is a side effect of furosemide, not a problem with HCTZ.

    03:16 So that's cool. Now electrolyte imbalances are still an issue as they are with all diuretics but with hydrochlorothiazide we're still going to watch our patient for low potassium, low sodium, and low chloride. That can be problematic with some other types of drugs. So watch for signs of electrolyte imbalances. Any diuretic, what it does, well it can do over well as I say and your patient might end up dehydrated. If they get too dehydrated, they can end up with hypotension, low blood pressure. Remember that dehydration, low blood pressure, then they're at risk for falling, orthostatic hypotension. So teach them "Hey go from lying to sitting and sitting to standing very slowly cause you might be a little dizzy." Hyperglycemia is an elevated blood sugar. Furosemide can cause that as can hydrochlorothiazide. So if your patient is diabetic, you want to monitor their blood sugar closely and if they have any problems controlling their blood sugar, they need to contact their healthcare provider. We talked about hyperuricemia. That means hyper, high; uric is uric acid; emia in the blood. When you have elevated uric acid in your blood, you're at risk for gout. So if your patient has a history of gout we want to watch that very very closely and again educate your patient if they have any problems with joint pain they need to contact their healthcare provider. Here's a sad news, it can also increase the LDL and decrease the HDL so we're going to keep an eye on those and all our patients. The last electrolyte we're talking about, this will also increase the excretion of magnesium. So we kind of grouped potassium, sodium, and chloride together because that's probably going to take the biggest hit but we didn't want you to miss that it can also increase the excretion of magnesium. So, the drug interactions with hydrochlorothiazide are also similar to loop diuretics. I love it when a plan comes together. This makes studying so much easier when you can look for things that are the same amongst drug families. So we know that hydrochlorothiazide causes a risk for low potassium.

    05:27 We know low potassium for any reason increases the risk for dig toxicity. So, if your patient is on hydrochlorothiazide and they're taking dig, you want to watch that really closely. Look for signs of low potassium and likely the health care provider will order some type of potassium replacement for your patient. Now, low sodium can cause an increased risk of lithium toxicity.

    05:53 Remember low sodium for any reason will cause the body to think "Hey, hang on to sodium" and if the patient is taking lithium they'll also hang on to the lithium so that's what increases the risk for lithium toxicity. Now, this isn't just trivia. This could be really open areas for test questions to be asked. You may get the name of a patient, the age of a patient, some multiple diagnoses and medications that they're on. You're expected as a professional nurse to recognize dangerous drug combinations. So these are 2 key ones to make sure that you have in your own brains.


    About the Lecture

    The lecture Hydrochlorothiazide (HCTZ) – Thiazide Diuretics (Nursing) by Rhonda Lawes is from the course Medications for Fluid and Electrolyte Imbalances (Nursing). It contains the following chapters:

    • HCTZ: Mechanism of Action (MOA)
    • Timing of Administration
    • Adverse Effects
    • Drug Interactions with HCTZ

    Included Quiz Questions

    1. Blocks sodium reabsorption
    2. Increases renal blood flow
    3. Increases excretion of potassium
    4. Reduces glomerular filtration
    1. 2-hour onset lasting up to 12 hours
    2. 1-hour onset lasting up to 14 hours
    3. < 1-hour onset lasting up to 8 hours
    4. 2-hour onset lasting up to 8 hours
    1. Risk for electrolyte imbalances
    2. Risk for ototoxicity
    3. Blood sugar elevation
    4. Risk for hypotension
    5. Increased uric acid levels

    Author of lecture Hydrochlorothiazide (HCTZ) – Thiazide Diuretics (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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