Overview
This lecture covers thiazide diuretics, their mechanisms of action, clinical uses, side effects, and key nursing responsibilities, focusing on concepts vital for exams and safe patient care.
Mechanism of Action
- Thiazide diuretics inhibit the sodium-chloride co-transporter in the early distal convoluted tubule (DCT) of the nephron.
- Blocking sodium and chloride reabsorption increases their concentration in urine, causing water retention in the filtrate and increased urination (diuresis).
- They are less potent than loop diuretics because the DCT handles only 5–7% of sodium reabsorption, compared to 25% in the loop of Henle.
- Thiazides are less effective in patients with compromised glomerular filtration rate (GFR).
Common Thiazide Diuretics & Nephron Anatomy
- Examples: hydrochlorothiazide, indapamide, chlorothiazide, metolazone, chlorthalidone.
- Nephron parts: afferent/efferent arterioles, glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct.
- Each nephron section manages filtration and reabsorption of water, ions, and wastes.
Electrolyte Imbalances & Side Effects
- Thiazides can cause hyponatremia (low sodium), hypokalemia (low potassium), and metabolic alkalosis.
- Enhanced calcium reabsorption can lead to hypercalcemia (high calcium levels).
- May increase blood glucose (hyperglycemia) and uric acid (hyperuricemia), raising the risk of gout attacks.
- Patients may require potassium supplements and should be educated to consume potassium-rich foods.
Clinical Uses
- First-line treatment for hypertension (high blood pressure).
- Used in managing heart failure to reduce fluid overload.
- Beneficial for recurrent renal stones (calcium type) and in patients with low blood calcium.
Nursing Responsibilities & Patient Education
- Monitor for dehydration (low BP, increased HR), strict intake/output measurement, and daily weights.
- Educate patients to monitor weight and notify provider if rapid gain (>3 lbs/day) occurs.
- Check labs before administration, especially potassium and sodium.
- Watch for digoxin or lithium toxicity if electrolyte imbalances are present.
- Teach patients to change positions slowly to prevent orthostatic hypotension.
- Schedule doses in the morning to avoid nocturia.
- Ensure patients have safe bathroom access to prevent falls.
Key Terms & Definitions
- Distal Convoluted Tubule (DCT) — the nephron segment where thiazide diuretics act.
- Sodium-Chloride Co-Transporter — protein channel blocked by thiazides, reducing sodium/chloride reabsorption.
- Hyponatremia — low sodium in blood.
- Hypokalemia — low potassium in blood.
- Hypercalcemia — high calcium in blood.
- Hyperglycemia — high blood sugar.
- Hyperuricemia — high uric acid in blood (risk for gout).
- Orthostatic Hypotension — drop in blood pressure from standing up quickly.
Action Items / Next Steps
- Complete the free quiz on thiazide diuretics.
- Review foods high in potassium and patient teaching points.
- Monitor lab values (electrolytes, blood glucose, uric acid) for patients on thiazides.