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Pharmacology · chapter 34 · Diuretic Drugs

Introduction to Diuretics

The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.

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Key points

  1. What diuretic therapy does

    Diuretic therapy decreases circulating blood volume to reduce blood pressure and resolve interstitial edema.

  2. Where each diuretic class acts

    Potassium-sparing diuretics inhibit sodium reabsorption in the collecting tubule, and thiazide and thiazide-like diuretics decrease sodium reabsorption in the distal convoluted tubule. Different diuretics are often used in combination to take advantage of the complementary effects of individual drugs.

  3. Diuretic braking

    Diuretic braking is a progressive decrease in urinary output after repeated doses of loop diuretics. This renal response is due in part to increased sodium reabsorption in the nephron.

  4. Loop diuretics in acute kidney injury

    Loop diuretics are most frequently prescribed for clients with acute kidney injury (AKI) to decrease the risk of additional kidney damage and the development of hypervolemia, or fluid overload (Hegde, 2020).

  5. Not for preventing AKI

    Diuretic therapy is not recommended for preventing AKI, and the effectiveness of the therapy is limited in clients with hypoalbuminemia.

  6. Thiazide-induced hyponatremia in older adults

    Thiazide diuretic therapy can result in severe hyponatremia, especially in older adults who also consume large amounts of water.

  7. Signs of hypernatremia

    Hypernatremia, serum sodium levels above the therapeutic range, can cause cognitive dysfunction ranging from lethargy and confusion to seizures. Other signs and symptoms include orthostatic blood pressure changes, tachycardia, oliguria, and dry mucous membranes.

  8. Severe hypokalemia

    Potassium levels less than 2.5 mEq/L produce severe muscle weakness, including effects on respiratory muscles and life-threatening electrocardiogram (ECG) changes.

  9. Loop and thiazide diuretics lose potassium

    Clients taking loop diuretics or thiazide diuretics are at risk for hypokalemia because these medications cause loss of potassium along with sodium.

  10. Potassium-sparing diuretics and hyperkalemia

    Hyperkalemia, or serum potassium levels that are higher than therapeutic, can develop with the use of potassium-sparing diuretics. Mild and moderate hyperkalemia can be asymptomatic, but life-threatening cardiac symptoms or paralysis can occur at levels greater than 6.5 mEq/L.

  11. Creatinine and kidney function

    It is completely cleared by the kidneys, which means that creatinine levels can be used to assess kidney function. Significant renal impairment may occur before the creatinine level increases.

  12. Uric acid and thiazides

    Elevated uric acid levels are associated with gout, which is associated with joint and soft tissue injury, most commonly in the big toe. Thiazide and thiazide-like diuretics increase reabsorption of this waste product in the proximal renal tubules.

  13. Oliguria threshold

    Therapeutic urine output is 30 mL/hour; an individual is considered oliguric if their urine output is less than 0.5 mL/kg/hour (Berry, 2022).

  14. Weight gain to report

    Report weight increase of more than 2–3 pounds per day or more than 5 pounds in 1 week.

Terms to know

Diuretic resistance
Diuretic resistance occurs when the maximum dose of a loop diuretic fails to produce the anticipated effect on fluid volume status because the successive doses of the drug trigger hypertrophy of the distal tubule, which increases sodium reabsorption.
Diuretic braking
Diuretic braking is a progressive decrease in urinary output after repeated doses of loop diuretics.
Nephrotic syndrome
Diuretic Therapy for Nephrotic Syndrome Nephrotic syndrome is a disorder associated with proteinuria, edema, and hypertension.
Hypokalemia
Hypokalemia, or serum potassium levels that are lower than therapeutic, causes muscle weakness.
Renal autoregulation
Intrinsic Renal Response to Fluid Volume Excess Increased fluid volume triggers an intrinsic response from the kidneys, referred to as renal autoregulation.

Practice questions

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  1. A client taking a loop diuretic reports new muscle weakness. Which laboratory result should the nurse check first?

    1. Serum uric acid
    2. Lipid profile
    3. Serum potassium
    4. Blood urea nitrogen

    Answer: Serum potassium

    Loop and thiazide diuretics cause loss of potassium along with sodium, and hypokalemia causes muscle weakness. Uric acid, lipids and BUN do not explain new muscle weakness.

  2. A client is started on a potassium-sparing diuretic. For which electrolyte imbalance should the nurse monitor?

    1. Hyperkalemia
    2. Hypokalemia
    3. Hypercalcemia
    4. Hypernatremia

    Answer: Hyperkalemia

    Hyperkalemia can develop with potassium-sparing diuretics and may be asymptomatic until it causes life-threatening cardiac symptoms. Hypokalemia is the risk with loop and thiazide diuretics.

  3. A nurse is teaching a client who is starting a diuretic at home. Which instructions should the nurse include? Select all that apply.

    1. Weigh yourself every day at the same time, on the same scale.
    2. Stop the drug if your ankles are no longer swollen.
    3. Take the drug early in the day.
    4. Change position slowly to avoid dizziness.
    5. Take over-the-counter supplements freely to replace lost minerals.

    Answer: Weigh yourself every day at the same time, on the same scale., Take the drug early in the day., Change position slowly to avoid dizziness.

    Clients take the diuretic early to avoid nocturia, weigh daily at the same time on the same scale, and change position slowly to avoid orthostatic hypotension. They should not stop the drug or take OTC products without consulting the provider.

  4. A client taking a diuretic calls to report a weight gain of 3 pounds since yesterday. What should the nurse tell the client?

    1. Drink more water to flush the kidneys.
    2. This is expected; recheck next week.
    3. Skip tomorrow's dose of the diuretic.
    4. This gain should be reported to the health care provider.

    Answer: This gain should be reported to the health care provider.

    Clients are taught to report a weight increase of more than 2–3 pounds per day or 5 pounds in a week. Waiting, skipping a dose or changing fluid intake on their own is not what the teaching says.

  5. An older adult client taking a thiazide diuretic drinks large amounts of water every day. The nurse should monitor this client closely for which problem?

    1. Hyperkalemia
    2. Severe hyponatremia
    3. Hyperfiltration
    4. Hypernatremia

    Answer: Severe hyponatremia

    Thiazide therapy can cause severe hyponatremia, especially in older adults who also drink large amounts of water. The other imbalances are not linked to this combination in the section.

  6. A client taking a diuretic should be taught to report which symptoms immediately? Select all that apply.

    1. Chest pain
    2. Difficulty breathing
    3. Urinating more often in the morning
    4. Significant decrease in urinary output
    5. Irregular heart rate

    Answer: Chest pain, Difficulty breathing, Significant decrease in urinary output, Irregular heart rate

    Concerning symptoms to report immediately include difficulty breathing, chest pain, lightheadedness, muscle weakness, confusion, significant decrease in urinary output and irregular heart rate. Increased urination after a morning dose is the expected effect.

Where every quote comes from

Section 34.1 Introduction to Diuretics of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.

The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.