Renal Medications: A USMLE Guide

Introduction

Renal medications play a crucial role in the management of various renal conditions and are commonly tested on the United States Medical Licensing Examination (USMLE). This guide aims to provide a comprehensive overview of the key renal medications, their mechanisms of action, indications, adverse effects, and important clinical considerations.

Diuretics

Loop Diuretics

• Examples: furosemide, bumetanide, torsemide
• Mechanism of action: Inhibit the Na+-K+-2Cl- co-transporter in the thick ascending limb of the loop of Henle, leading to increased sodium, potassium, and water excretion.
• Indications: Edematous states (e.g., heart failure, cirrhosis, renal failure), hypertension, hypercalcemia.
• Adverse effects: Hypokalemia, hypocalcemia, ototoxicity, allergic reactions, volume depletion.
• Important clinical considerations: Monitor electrolytes and renal function regularly. Furosemide is also used in acute pulmonary edema.

Thiazide Diuretics

• Examples: hydrochlorothiazide, chlorothiazide
• Mechanism of action: Inhibit the Na+-Cl- co-transporter in the distal convoluted tubule, leading to increased sodium, potassium, and water excretion.
• Indications: Hypertension, heart failure, nephrolithiasis (calcium oxalate stones), diabetes insipidus.
• Adverse effects: Hypokalemia, hyponatremia, hypercalcemia, hyperuricemia, hyperglycemia.
• Important clinical considerations: Avoid in patients with renal impairment. Hydrochlorothiazide is commonly used as an initial treatment for essential hypertension.

Potassium-Sparing Diuretics

• Examples: spironolactone, eplerenone, amiloride, triamterene
• Mechanism of action: Antagonize the effects of aldosterone in the collecting tubules, leading to decreased sodium reabsorption and potassium retention.
• Indications: Heart failure, hypertension, hyperaldosteronism, cirrhosis.
• Adverse effects: Hyperkalemia, gynecomastia (spironolactone), renal impairment (triamterene).
• Important clinical considerations: Can be used in combination with thiazide or loop diuretics to counteract potassium loss. Spironolactone is contraindicated in patients with significant renal impairment.

Renin-Angiotensin-Aldosterone System (RAAS) Inhibitors

Angiotensin-Converting Enzyme (ACE) Inhibitors

• Examples: lisinopril, enalapril, captopril
• Mechanism of action: Inhibit the conversion of angiotensin I to angiotensin II, preventing vasoconstriction and aldosterone release.
• Indications: Hypertension, heart failure, diabetic nephropathy, myocardial infarction.
• Adverse effects: Dry cough, angioedema, hyperkalemia, acute renal failure.
• Important clinical considerations: Contraindicated in pregnancy. Captopril can cause a rash and taste disturbances.

Angiotensin II Receptor Blockers (ARBs)

• Examples: losartan, valsartan, irbesartan
• Mechanism of action: Block the angiotensin II receptor, leading to vasodilation and reduced aldosterone release.
• Indications: Hypertension, heart failure, diabetic nephropathy.
• Adverse effects: Hyperkalemia, acute renal failure (rare).
• Important clinical considerations: Generally better tolerated than ACE inhibitors, with no cough side effect.

calcium channel Blockers

Dihydropyridines

• Examples: amlodipine, nifedipine
• Mechanism of action: Block L-type calcium channels in vascular smooth muscle, leading to vasodilation.
• Indications: Hypertension, angina pectoris, Raynaud's phenomenon.
• Adverse effects: Peripheral edema, flushing, headache, reflex tachycardia.
• Important clinical considerations: Dihydropyridines have minimal negative cardiac inotropic effects but may cause reflex tachycardia.

Non-Dihydropyridines

• Examples: verapamil, diltiazem
• Mechanism of action: Block L-type calcium channels in cardiac muscle and vascular smooth muscle, leading to vasodilation and negative inotropic effects.
• Indications: Hypertension, angina pectoris, supraventricular tachycardia.
• Adverse effects: Bradycard