Diuretics Flashcards
Classification of diuretics
High ceiling or loop diuretics
Medium efficacy
Adjunctive / weak diuretics
Examples of high ceiling diuretics
Furosemide
Bumetanide
Torasemide
Sub classification of medium efficacy diuretics and examples
Benzothiadiazines: hydrochlorothiazide, hydroflumethazide
Thiazide like: chlorthalidone, metolazone, xipamide, indapamide, clopamide
Sub classification of weak diuretics and examples
CAse inhibitors: acetazolamide
K+ sparing:
Aldosterone antagonist- spironolactone
Renal epithelial Na+ Chanel inhibitors- amiloride, triamterene
Osmotic diuretics: mannitol, glycerol, isosorbide
Duration of action of furosemide
3-6 hours (short)
Site of action of furosemide
Thick Ascending limb of LOH inhibiting Na+-k+-2cl- cotransport
Action of furosemide in corticomedullary osmotic gradient and free water clearance
Corticomedullary osmotic gradient is abolished and positive and negative free water clearance is blocked
Action of furosemide in gfr and rbf
Rbf increases, gfr same
Why is furosemide used in LVF and pulmonary edema
Intravenous furosemide causes prompt increase in systemic venous capacitance which decreases Left ventricular pressure.
What happens to ca and mg in furosemide action
Ca and mg both decreases
Which drug is 40 times more potent than furosemide, highly effective in pulmonary edema and induced very rapid diuresis. It is preferred for oral absorption in CHF, as it is not affected by edema of the bowels
Bumetanide
Torasemide is used in
Edema and hypertension
Uses of high ceiling diuretics
Edema
Acute pulmonary edema (LVF, After MI)
Cerebral edema
Hypertension
Blood transfusion
Hypercalcemia of malignancy
Site of action of thiazide diuretics
Cortical diluting segment or early DT
Inhibits Na+-CL- symport
Action of thiazides on free water clearance and corticomedullary osmotic gradient
Corticomedullary osmotic gradient not affected
Positive free water clearance reduced
Negative free water clearance not affected
Action of thiazides on gfr
Reduces gfr
Action of thiazides on ca and mg
Ca excretion decreases
Mg excretion increases
Duration of action of thiazides
6-48 hours varies
Examples of thiazides
Chlorthalidone
Metolazone
Xipamide
Indapamide
Uses of thiazides
Edema
Hypertension
Diabetes insipidus
Hypercalciuria
Complications of high ceiling and thiazides
Hypokalemia
Acute saline depletion
Dilutional hyponatremia
GIT and CNS disturbances
Allergic reaction
Hearing loss
Dyslipedemia and hyperglycemia
Hyperuricemia
Magnesium depletion
Hypocalcemia (loop diuretics only)
Aggravated renal insufficiency (thiazides only)
Toxemia of pregnancy
Mental disturbances
Interactions of thiazides and high ceiling diuretics
Potentiate all hypertensives
Hypokalemia enhances digoxin toxicity, reduces sulphonyl urea action, increases risk of polymorphic ventricular tachycardia due to drugs which prolong Q-t interval
High ceiling diuretics and aminoglycoside antibiotic and both ototoxic and nephrotixic with concurrent use
Indomethacin and NSAID inhibits PG synthesis and diminish action of loop diuretics
Probencid inhibits diuretic action
CA present in
Renal tubular cell (PCT)
Gastric mucosa
Exocrine pancreas
Ciliary body of eye
Brain
RBC
Examples of CAse inhibitor
Acetazolamide
Methazolamide
Dichlorphenamide
Uses of CAse inhibitors
Glaucoma
Epilepsy
Mountain sickness
To alkalinise urine
Periodic paralysis
Extra renal actions of acetazolamide
Lowers Intraocular tension
Decrease gastric HCL secretion
Raised level of Co2 in brain which decreases PH
Alteration of Co2 transport in lungs and tissues
Why is acetazolamide not used as a diuretic
Because of its self limiting action, production of acidosis and Hypokalemia
Two classes of K+ sparing diuretics with examples
Aldosterone antagonist - spironolactone, eplerenone
Renal epithelial Na+ channel inhibitors- amiloride, triamterene
Spironolactone MOA
Inhibits formation of AIP by combining with Mineralocorticoid receptor (MR)
Spironolactone actions
Increases Na+ secretion
Decreases K+ excretion
Mild saluretic
Increases Ca2+ excretion
Most important active metabolite of spironolactone
Canrenone
Uses of spironolactone
Edema
To counter act K+ loss due to other diuretics
Hypertension
CHF
Primary hyperaldosteronism
Interactions of spironoloactone
Spironolactone + k+ supplements give hyperkalemia
Aspirin blocks it by inhibiting synthesis of canrenone
Hyperkalemia in presence of ACe inhibitors
Increases plasma digoxin concentration
Most serious problem with spironolactone
Hyperkalemia
And testosterone action
Alternative to spironolactone which has no androgen and progesterone action
Eplerenone
Renal epithelial Na+ channel inhibitors example
Triamterene and amiloride
Most important adverse effect of traimterene and amiloride
Hyperkalemia
Uses of mannitol
- In increased intracranial or intra ocular tension
- To maintain gfr
- To counteract low osmlolality of plasma ecf due to rapid haemodialysis
