Diuretics Pharmacology Quiz

Diuretics

• Diuretics are drugs that increase renal excretion of sodium and water, leading to a rise in urine volume.
• Most diuretics work by interfering with the kidney's normal sodium handling.
• Diuretic targets are specific membrane transport proteins in renal tubular epithelial cells.
• Diuretics are categorized into different types (e.g., carbonic anhydrase inhibitors, loop diuretics, thiazides, osmotic diuretics, potassium-sparing diuretics.) Each type has a unique mechanism of action, sites of action, and effects on the body.
• The five functional areas along a nephron are the proximal convoluted tubule, descending loop of Henle, ascending loop of Henle, distal convoluted tubule, and the collecting tubule and duct.
• The kidney is responsible for regulating fluids and electrolytes primarily through glomerular filtration, passive tubular re-absorption, and active tubular secretion. These processes facilitate water and solute homeostasis.

Kidney Function

• The kidney excretes metabolic wastes, regulates acid-base balance, maintains osmolarity, controls blood pressure, and secretes hormones.
• A nephron is the functional unit of the kidney, comprising a glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

Carbonic Anhydrase Inhibitors

• Acetazolamide and dorzolamide are carbonic anhydrase inhibitors.
• They inhibit carbonic anhydrase in the proximal convoluted tubule, thereby interfering with sodium bicarbonate reabsorption, leading to diuresis.
• These drugs cause a weaker diuretic effect, but cause alkaline urine and excretion of bicarbonate.

Osmotic Diuretics

• Mannitol and urea are osmotic diuretics.
• These hydrophilic substances are extensively filtered by the glomerulus and are poorly reabsorbed, leading to an increase in the osmolarity of the tubular fluid. This high osmolarity prevents further water reabsorption; promoting water excretion.
• Mannitol is administered intravenously and is primarily used to reduce intracranial pressure.

Loop Diuretics

• Furosemide, torsemide, bumetanide, and ethacrynic acid are loop diuretics. These are highly effective diuretics.
• They inhibit Na+/K+/2Cl- co-transporter in the thick ascending loop of Henle, disrupting the reabsorption of sodium, potassium, and chloride.
• They are used in emergency situations for acute pulmonary edema, heart failure, and hyperkalemia.

Thiazide Diuretics

• Thiazides, such as chlorothiazide, hydrochlorothiazide, indapamide, and metolazone, are commonly used to treat hypertension.
• They inhibit Na+/Cl co-transporter in the cortical region of the ascending loop of Henle and distal convoluted tubule, increasing sodium and chloride excretion.
• Thiazide diuretics have a moderate diuretic effect and a relatively longer duration of action.

Potassium-Sparing Diuretics

• Spironolactone and eplerenone are aldosterone antagonists.
• They block aldosterone's effect at the intracellular receptor, thus preventing sodium channels and Na+/K+ ATPase activity; reducing sodium reabsorption and leading to increased excretion of potassium.
• Amiloride and triamterene block sodium channels, preventing sodium reabsorption.
• Potassium-sparing diuretics are often used in conjunction with thiazide or loop diuretics to prevent potassium loss.

Adverse Effects of Diuretics

• Adverse effects for common diuretic classes include hypokalemia, metabolic acidosis, renal stone formation, and hypersensitivity reactions

Therapeutic Uses of Diuretics

• Therapeutic uses vary for different diuretic classes, and treatment of high blood pressure, heart conditions, glaucoma and other conditions.

Renal Anatomy and Function

• The kidney regulates body fluid and electrolyte balance, and is crucial in homeostasis.
• Nephrons are the functional units of the kidney. They contain specialized channels and pumps to filter and regulate the reabsorption of solutes.

Terminology in Nephron Function

• Reabsorption: The process of transporting solutes and water from the filtrate back into the bloodstream.
• Secretion: The process of transporting solutes from the bloodstream into the filtrate.
• Filtration: The process of filtering blood to produce the initial filtrate for urine production.