Lecture 16 - Diuretics and Antihypertensive Drugs Flashcards
Renal Physiology
What occurs during the filtration of blood?
Waste products, toxins, and excess substances, such as electrolytes and water, are filtered from the bloodstream to form urine
Renal Physiology
What is regulated?
- Sodium, potassium, calcium, and phosphate
- Balance body fluid by adjusting the amount of water
- regulate blood pressure
Renal Physiology
What are the functions of the renal system?
- Filtration of blood
- regulation of electrolytes, fluid balance, and blood pressure
- Production of hormones
- Acid-Base balance
- Excretion of waste products and detoxification
- Pheromone secretion
Where does urine formation take place?
In the nephrons within the kidneys (includes filtration, reabsorption and secretion)
What are the steps in urine formation?
- Glomerular filtration - creates a plasmalike filtrate of the blood
- Tubular reabsorption - Removes useful solutes from the filtrate and returns them to the blood
- Tubular secretion - Removes additonal wastes from the blood and adds them to the filtrate
- Water conservation - Removes water from the urine and returns it to the blood; concentrates wastes
What substances can pass through the filter?
Water, electrolytes, glucose, amino acids, fatty acids, vitamins, urea, uric acid, creatinine (anything < 8 nm)
How are sodium and chloride ions reabsorbed?
Cation exchange and chloride ion transport
How is Water reabsorbed?
Within the proximal convoluted yubules and the collecting ducts. Water rushes toward sodium ions in the blood through aquaporins.
Role of kidney in regulating acid-base balance
How does the kidney regulate acid-base balance?
CO2 + H2O –carbonic anhydrase–> H+ + HCO-3
- H+ gets secreted
- HCO3- is reabsorbed as a buffer and added to extracellular fluid
What are diuretics used to manage?
- Anuria
- Hypertension
- Heart failure
- Edema
What are the classes of diuretics?
- Osmotic agents
- carbonic anhydrase inhibitors
- Thiazide and thiazide-like compounds
- Organic acids (loop diuretics)
- Potassium-sparing diuretics
- ADH antagonists
What is the site of action of Osmotic diuretics?
Glomerulus
What is the site of action of Carbonic anhydrase inhibitors?
Proximal convoluted tube
What is the site of action of Loop diuretics?
Ascending limb of the nephron loop
What is the site of action of Thiazide/thiazide-like diuretics?
Distal convoluted tube
Osmotic diuretics - Mechanism of action
Acts osmotically by attracting fluid from edematous tissues –> creates an osmotic gradient within the renal tubular lumen to prevent water reabsorption. Osmotic diuretics cannot cross tubular membrane. Produces a mild diuresis with no alteration in electrolyte or acid-base balance
Osmotic diuretics - Indication
Treatment of anuria, oliguria, acute kidney injury, cerebral edema, drug toxificity management
Osmotic Diuretics - Drug examples
Glycerin, isosorbide, mannitol
Carbonic Anhydrase inhibitor - Mechanism of action
Inhibition of carbonic anhydrase –> results in excretion of sodium ions into urine
Distal convoluted tubules increase the secretion of potassium ions –> leads to increased level of potassium in the urine (hypokalemia)
How do carbonic anhydrase inhibitors affect the acid-base balance?
- Prodiction of bicarbonate ions is inhibited –> metabolic acidosis (increased pH in body due to increase of bicarbonate in blood) may occur
Carbonic anhydrase inhibitors - Indication
- Weakest of the diuretics
- Main use is in the treatment of glaucoma
Carbonic anhydrase inhibitors - Drug examples
Acetazolamide - inhibits both isoforms inhibits both isoforms of carbonic anhydrase; the decreased carbonic anhydrase activity results in decreased
Na+ and HCO3– absorption
Loop diuretics - Mechanism of action
Inhibits sodium and chloride ion transport in the loop of Henle
- significant loss of sodium, potassium, chloride, and water occurs
- Targets NKCC2
-VERY efficient diuretics (highest capacity of diuresis
Loop diuretics - Drug examples
Bumetanide, ethacrynic acid, furosemide, and torsemide