pharmacology Flashcards
where is blood filtered in the kidney?
glomerulus
what is natiuresis?
the process of excretion of sodium in the urine
what increases sodium excretion?
ventricular and atrial natriuretic peptides as well as calcitonin
what conserves sodium?
chemicals such as aldosterone
where is K appearing in the urine secreted from?
the collecting duct
where is filtered potassium reabsorbed?
the proximal tubule and the loop of henle
how is potassium transported into cells in the collecting duct?
via the N/K ATPase on the basolateral membrane
what are diuretics?
drugs that ↑ the volume of urine produced by promoting the excretion of Na+, Cl-, HCO3 and water from the kidneys.
what is the impact of diuretics?
↑ urine flow, altered pH and altered ionic composition of blood and urine
when are diuretics used?
treatment of oedema and hypertension
what are the different classes of diuretics?
Osmotic diuretics
Carbonic anhydrase inhibitors
Loop diuretics
Thiazide diuretics
Potassium sparing diuretics
where do osmotic diuretics act?
proximal tubules
loop of henle
collecting duct
what is the mechanism of osmotic diuretics?
inhibition of water and Na reabsorption
where do carbonic anhydrase inhibitors act?
the proximal tubules
what is the mechanism of carbonic anhydrase inhibitors?
inhibition of bicarbonate reabsorption
where do loop diuretics act?
loop of henle (thick ascending limb)
what is the mechanism of loop diuretics?
inhibition of Na, K and Cl
where do thiazides act?
early distal tubule
what is the mechanism of thiazides?
inhibition of Na and Cl cotransport
where do K sparing diuretics act?
late distal tubule
collecting duct
what is the mechanism of K sparing diuretics?
inhibition of Na reabsorption and K secretion
what are some examples of osmotic diuretics?
mannitol, isosorbide, glycerine and urea
what is the result of osmotic diuresis?
blood volume deacreased and a large volume of dilute urine produced
what does mannitol do?
diuresis in the prevention of acute renal failure
excretion of toxic substances
reduce IOP and ICP and cerebral oedema
what are the adverse effects of osmotic diuresis?
cardiovascular toxicity immediately after injection
contraindicated in patients with HF
what are some examples of carbonic anhydrase inhibitors?
Acetazolamide, Methazolamide
what is the function of carbonic anhydrase in the proximal collecting tubule?
anhydrase plays a major role in acid/base balance
ultimately leads to no Na or bicarbonate reabsorption
what are some indications for carbonic anhydrase inhibitors?
raised IOP in open angle glaucoma
ocular hypertension when monotherapy is inadequate
what are some side affects of carbonic anhydrase inhibitors?
metabolic acidosis
renal stones
renal potassium wasting
which binding site do loop diuretics act upon?
the chloride binding site, directly inhibiting the carrier
what are the indications for loop diuretics?
water imbalances associated with congestive HF, KF and pulmonary oedema
in patients with a high BP and less than 50% kidney function
how do loop diuretics interact with other medications?
hypokalaemia associated with loop diuretics increases the risk of digoxin toxicity ( a med prescribed for congestive HF)
corticosteroids can also cause hypokalaemia
aminoglycosides can increase the risk of kidney damage
NSAIDs can reduce the effect of loop diuretics
what are some examples of thiazide diuretics?
hydrochlorothiazide, bendroflumethiazide
what are thiazide diuretics used to treat?
high BP
congestive HF
oedema
cirrhosis
what ion do thiazides increase reabsorption of?
Ca reabsorption at the distal tubule
what are the contraindications of thiazide diuretics?
hypotension
gout
renal failure
lithium therapy
hypokalaemia
may worsen diabetes
they reduce the clearance of uric acid, hence the gout contraindication
why can thiazides and loop diuretics lead to digoxin toxicity?
Hypokalaemia resulting from loop diuretics and thiazides will potentiate the effect digoxin, thus increasing the risk of cardiac arrythmias
how does digoxin work?
Digoxin is an inhibitor of the Na+/K+ ATPase pump and binds to the alpha subunit.
This causes an increase in intracellular Na+
which diuretics are potassium sparing?
aldosterone antagonists (eg spironolactone)
sodium channel inhibitors (eg amiloride)
what are the side affects of potassium sparing diuretics?
hyperkalaemia
use with caution with meds that increase K, eg. ACEi
which drugs reduce the efficacy of thiazides?
NSAIDs
what does pharmacodynamics mean?
effects of drug on the body
