DIURETICS / Types / Examples / Pharmacology / Pharm D slides

Definition: Diuretics are medications that promote the excretion of water and electrolytes from the body through urine, helping to reduce blood pressure and fluid overload.
Types of Diuretics:
Thiazide Diuretics – e.g., hydrochlorothiazide; used in hypertension.
Loop Diuretics – e.g., furosemide; used in edema and heart failure.
Potassium-Sparing Diuretics – e.g., spironolactone; prevent potassium loss.

1. DIURETICS P. Harshitha Reddy

2. DIURETICS Definition: Diuretics are medications that promote the excretion of water and electrolytes from the body through urine, helping to reduce blood pressure and fluid overload. Types of Diuretics: Thiazide Diuretics – e.g., hydrochlorothiazide; used in hypertension. Loop Diuretics – e.g., furosemide ; used in edema and heart failure. Potassium-Sparing Diuretics – e.g., spironolactone ; prevent potassium loss.

3. THIAZIDES DIURETICS Thiazides Examples: Hydrochlorothiazide, Chlorthalidone , Chlorothiazide Used in: Uncomplicated hypertension (HTN) Advantages: Long duration of action Effective at low doses (e.g., 12.5 mg of chlorthalidone or hydrochlorothiazide) If the antihypertensive response is inadequate, the dose can be increased to 25 mg/day Note: Beyond this dose, thiazides are not safe

4. Thiazides Onset of effect: Develops over 2–4 weeks Combination therapy: Potassium-sparing diuretics are often co-administered with thiazides to: Counteract potassium ion (K⁺) loss Enhance antihypertensive efficacy

5. Mechanism of Action of Thiazides Inhibit Na⁺/ Cl ⁻ symporter in the early distal convoluted tubule (DCT) Promote Na⁺ and H₂O excretion Chronic use: Reduces Na⁺ concentration in vascular smooth muscle → Decreases peripheral vascular resistance (PVR) → ↓ Blood Pressure (BP) Also decreases cardiac output (CO)

6. Adverse Effects of Thiazides Hypokalemia Hypercalcemia Hyperglycemia Hyperuricemia Hyperlipidemia Impotence Decreased libido

7. Advantages of Thiazides as Antihypertensives Long duration of action Cost-effective Well-tolerated by elderly patients Decrease the incidence of fractures by reducing urinary calcium excretion Show synergistic effects when combined with other antihypertensives Chlorthalidone : Most frequently used thiazide due to its long duration of action Indapamide & Metolazone : More potent, longer acting, and cause fewer adverse effects than other thiazides

8. LOOP DIURETICS Have a short duration of action Sustained Na⁺ deficit is not maintained Not used routinely in HTN management except in cases of renal or cardiac failure.

9. POTASSIUM SPARING DIURETICS Used in combination with Thiazides or loop diuretics to enhance antihypertensive efficacy and prevent hypokalaemia .