Pharmacology Flashcards
What is natriuresis
Process of excretion of sodium in the urine via action of the kidneys
What factors promotes natriuresis
Ventricular natriuretic peptide
ANP
Calcitonin
Ventricular natriuretic peptide is secreted by
Ventricular myocardium of the heart due to stretches of the wall
What factors inhibit natriuresis
Aldosterone
Inhibiting natriuresis =
Conserving sodium -> increase in blood volume due to osmosis
Promoting natriuresis =
Decrease in sodium in blood -> decrease in blood volume due to osmosis (water follows sodium) -> increase in urine production
Why is K+ balance important
Because K+ can effect the functions of excitable cells such as muscle cells (Na K pump maintains the potential gradient of the cell)
How does the kidneys maintain K+ balance
mechanism of diuretics
Drugs that increases the volume of urine by promoting excretion of Na+, Cl-, HCO3 and water
Net result = increase in urine flow and altered pH and ionic composition (because it takes other ions with it as well)
Diuretics causes increase in urine volume but this also means it can take other ions with it. What is a side effect of diuretic
Hypokalaemia - due to increased excretion of urine = increased excretion of K+
Symptoms of hypokalaemia
Muscle cramps & pain
Palpitations
Constipation
Arrhythmias
Rhabdomyolysis
What arrhythmia is seen in hypokalaemia
Flat T waves
ST depression
Prominent U waves
Prolonged PR
Types of diuretics
Osmotic diuretics
Carbonic anhydrase inhibitors
Loop diuretics
Thiazide
K+ sparing diuretics
Site of action of osmotic diuretics
Proximal tubule
Loop of Henle
Collecting duct
What is the mechanism of action of osmotic diuretics
Inhibition of water and Na+ reabsorption
Examples of osmotic diuretics
Mannitol
Isosorbide
Glycerine
Which osmotic diuretic is only given through IV injections and why
Mannitol
because body cells lack transport mechanisms for it hence it won’t be able to penetrate cell membranes
Which osmotic diuretic is the most preferred
Mannitol
Indications of osmotic diuretic
Prevent acute renal failure - Mannitol
Reduce intraocular pressure
Reduce intracranial pressure - Mannitol and urea
Reduce cerebral edema - Mannitol and urea
Side effects of osmotic diuretic
Cardiovascular toxicity
- injection causes osmosis of non-vascular fluids into the vessel
- increases blood volume
- increases workload of the heart
Contraindication of osmotic diuretic
Patients with congestive heart failure
Examples of carbonic anhydrase inhibitors
Acetazolamide
Methazolamide
Site of action of carbonic anhydrase inhibitors
Proximal tubule
What is the role of carbonic anhydrase in proximal tubules
- Carbonic anhydrase forms H2CO3 in cell from CO2 + H2O
- H2CO3 then dissociates into HCO3- and H+
- HCO3- is reabsorbed = conserved
- With each H+ is excreted, a Na+ is reabsorbed = retention of water
