Potassium Excreting (wasting) Diurectics Flashcards
What are the extra renal diuretics?
Water Alcohol Digitalis Dopamine (low dose) Colloids
Which are the K+ excreting diuretics?
CAIs
Loops
Thiazides
Name the CAIs
Acetazolamide
Dorzolamide
Brinzolamide
Name the loop diuretics
Furosemide
Bumetanide
Torsemide
Ethacrynic acid
What are the clinical indications of loop diuretics?
Acute pulmonary Edema CHF Refractory Edema Acute/chronic kidney failure Hypertension Poisoning Anion overdose Hypercalcemic states
What are the adverse effects of loop diuretics?
Hypokalemia Metabolic alkalosis Hypocalcemia Hypomagnesemia Hyperuricemia Transient deafness Secondary hyperaldosteronism Sulphonamide hypersensitivity Ototoxicity
What are the drug interactions of loops diuretics?
NSAIDs decrease their effect
Aminoglycosides may enhance their effect
They enhance the effects of muscle relaxants
How are loops administered?
Oral
Parenteral
What is the dose of furosemide?
20-40mg in the morning
What is the dose of furosemide when the GFR <20 (kidney insufficiency)?
500mg
What is the half life of loops?
Short half life
What is the half life of Furosemide?
2-3h
What are the pharmakinetic features of loops?
They act on the luminal side therefore their activity correlates with GFR
What are the clinical uses of CAIs?
Glaucoma Acute mountain sickness prophylaxis Metabolic alkalosis Urinary alkalisation Severe hyperphosphatemia
What are clinical indications of CAIs when used as adjacent therapy?
Epilepsy
Refractory Edema
CSF leakage
When would we use CAIs in case of poisoning?
Why?
We would use CAIs when we are trying to eliminate a weak acid. E.g., aspirin poisoning
Because CAIs promote the Alkalisation of the urine which promotes the excretion of weak acids
Why are CAIs indicated in glaucoma?
CA is involved in the production of aqueous humour. Therefore there is decreased AH production which reduces the IOP.
In which type of glaucoma do we use CAIs?
Chronic open angle glaucoma
How are CAIs administered?
Oral
IV
How are CAIs eliminated?
Renal elimination - active tubular secretion + passive reabsorption
What is the percentage of protein bound CAIs?
90%
What are the extra-renal actions of CAIs?
Decreased production of aqueous humour
Decreased production of CSF
Decreased production of gastric and pancreatic juice
What are the contraindications of CAIs?
Sulphonamide sensitivity
Severe kidney or hepatic disorders
What are the adverse effects of CAIs?
Hyperchloremic metabolic acidosis Hypokalemia Paresthesia Somnolence Renal stones (Ca-phosphate, cysteine) Sulphonamide sensitivity
Name the Thiazides
Bendroflumethiazide
Hydrochlorothiazide
What are the clinical indications of Thiazides?
CHF Hypertension (1st line) Edema Idiopathic hypercalciuria (kidney stones) Nephrogenic diabetes insipidus Nephrolithiasis
What are the adverse effects of thiazides?
Hypokalemia Hypercalcemia Hypomagnesemia Hyperuricemia Metabolic alkalosis Impaired glucose tolerance Weakness Hypersensitivity Secondary hyperaldosteronism
Why is hyperuricemia an adverse effect of thiazide usage?
Thiazides increase serum Uric acid by decreasing acid secreted by the organic acids secretory system which can result in gout.
Which side of the nephron do Thiazides work on?
The luminal side
How is Indapamide eliminated?
Partly via bile
How are thiazides administered?
Orally
Do Thiazides have a longer or shorter half life?
Longer half life
What is the dose of Hydrochlorothiazide in hypertension?
6.25-25mg
What is the dose of Hydrochlorothiazide in CHF?
25-100mg
Which CAIs can be used in epilepsy?
Dorzolamide
Brinzolamide
Why do we never use CAIs alone?
They are very weak and tolerance develops very quickly. Use only for short term application
Where in the nephron do CAIs act?
PCT
Where in the kidney do loop diuretics work?
Thick ascending loop
Where in the kidney do thiazides act?
Distal tubule
How are CAIs administered in the treatment of glaucoma?
Topically
Why are renal stones a side effect of CAIs use?
CAIs creates alkalisation of the urine. Calcium phosphate stones are more likely to form in alkaline urine.
Which loop can we use if the patient has a sulphonamide hypersensitivity?
Ethacrynic acid
Why are thiazides used in nephrolithiasis?
Because thiazides lower the amount of urinary calcium
Why are calcium phosphate stones likely to form in CAI usage?
Because calcium phosphate stones are more likely to form in an alkaline urine
What is the mechanism of action of loops?
they inhibit the sodium/potassium/2 chloride transporter
Where do loops work?
thick ascending limb
Where do CAI work?
PCT
Where do thiazides work?
Distal nubile
Do loops loose or reabsorb calcium?
Loops loose calcium
When shouldn’t loops be used and why?
Should not be used in osteoporosis because they loose calcium
Do thiazides promote or decrease calcium excretion?
Thiazides decrease calcium excretion
what is the effect of thiazides on on smooth muscle cells?
They hyperpolarize smooth muscle cells causing vasodilation
What is the effect of thiazides on beta cells of the pancreas?
they decrease insulin release - hyperglycaemia
Why do thiazides cause hyperglycaemia?
Because they prevent insulin release from beta cells of the pancreas
What is the mechanism of action of thiazides?
they inhibit the Sodium/Cl co-transporter in the distal tubule
What is the result of thiazide use?
Sodium and chloride loss
What are thiazide drug interactions?
They interact with digitoxin leading to increased toxicity due to electrolyte disturbances
When should thiazides be avoided and why?
In patients with DM
Because they inhibit insulin release from beta cells of the pancreas
