Diuretics & renal drugs Flashcards
How does Acetazdamide work as a diuretic?
Carbonic anhydrase inhibitor- inhibits HCO3- breakdown to H20 and CO2 to less HCO3- reabsorbtion so less H20 reaborbtion
Name one osmotic diuretic
Mannitol
How does amilloride work
Inhibits ENaC in DCT and also NHE in proximal tubule (minor effect), so less sodium and so less water reaborption
Name one loop diuretic and the channel it acts on?
Furosemide acts on NKCC
Name 2 thiazide diuretics
Chlorothiazide, indapamine, bendroflumethiazide
Name 2 ADH antagonists
Tolvaptan and lithium, others in caffine and alcohol
How does bumetanide work?
Loop diuretic- inhibits NCCK, is more potent than furosemide
How do ADH antagonists act? When are they used?
Inhibit ADH, so less opening of AQP in distal tubules, so less water reabsorbed. Used in treatment of hyponaturaemia as cause water excretion but not sodium excretion.
Give 3 general ADRs of diuretics
- anaphylaxis
- hypovolaemia leading to hypotension (AKI)
- electrolyte disturbances (k+, Mg+, Na+, Ca2+)
- some metabolic disturbances
Give 3 ADRs specific to loop diuretics
- Gout
- Hypokalaemia an alkalosis
- ototoxic in large quantities
- increased LDL and TAG
Give 3 ADRs specific to thiazide diuretics
- Gout
- hypokalaemia and akalosis
- erectile dysfunction
- hypercalcaemia
- hyperglyacemia (reduced insulin sensitivity)
give 3 ADRs specific to spironolactone
- hyperkalaemia–> acidosis
- impotence
- painful breast tissue enlargement in men
Describe the consequence of prescribing an ACEi and a K+ sparing diuretic like amiloride
Both will decrease K+ excretion leading to hyperkalaemia and so cardiac problems
Describe the consequence of prescribing digoxin and a thiazide or loop diuretic
Diuretic leads to hypokalaemia, this leads to increased digoxin binding and toxicity, which in turn leads to cardiac problems
What is the risk of prescribing Loop/ thiazide diruetics with steroids?
Both will increase risk of hypokalaemia, due to steroids mineralocorticoid effect to up regulate ENaC and so increase ROMK activity and the diuretics effect to increase distal salt delivery.
Give 5 uses for diuretics, and state the type of diuretic most commonly indicated
- Hypertension (usually thiazide as has additional vasodilatory properties)
- Heart failure (usually loop diuretics as are most powerful so clear odema well, spironolactone indicated for benefits in heart remodelling)
- decompensated liver disease (spironolocatone or loop to clear ascites, hypertension etc)
- Nephrotic syndrome (loop + others to reduce odema caused by albumin loss)
- CKD (loop +/- thiazide beneficial to clear fluid retention as well as prevent hyperkalaemia due to poorer removal of K+)
Why may diuretics not work very well in nephrotic syndrome
- odema in gut means less absorbtion of drug (may need IV)
- less albumin in drug reduces its half life
- If renal failure- poorer reuptake of drug so just piss it out
What dietary factor may reduce diuretic action?
high salt diet- offsets extra Na+ losses from diuretic
Give 3 nephrotoxic drugs
aminoglycosides, vancomycin, aciclovir, NSAIDS, many/ most drugs
Give 2 common drugs which may worsen GFR?
- ACEi and ARB–> Angiotensin 2 needed for efferent vasoconstriction, less of this= less GFR
- NSAIDS–> prosaglandins important in afferent vasodilation, this is inhibited= less GFR
Give 3 causes of hyperkalaemia
- Acidosis or muscle damage causing release from cells
- reduced GFR (AKI), increased distal Na+ delivery (diuretics)
- Drugs (ACEi, Spironolactone, ARB, NSAIDS, amiloride, trimethoprim)
Describe the signs and symptoms of hyperkalaemia
- tiredness or weakness
- numbness and tingling
- N+V
- trouble breathing
- chest pain
- palpitations
Describe the ECG changes of hyperkalaemia
- 1st sign = tall tented T waves, prolonged PR
- 2nd= ST elevation, loss of P wave, widened QRS, ectopic beats
- 3rd= QRS widens more and peaks lower, T wave widens until just looks like 3 large waves, leads to V. fib, asytole
How would you treat hyperkalaemia (3)
- give calcium gluconate to protect heart
- Give insulin and dextrose to lower serum K+
- give calcium resonuim or thiazide/ loop diuretic to increase K+ removal
- Can also give salbutamol if no insulin and dextrose, rarely NaCO3 will be given for acidosis
