Medicines and the Kidney Flashcards
Where might drugs become highly concentrated? And what might this cause?
Loop of Henle
Tubular toxicity
What does drug elimination depend on?
- Glomerular filtration
- Tubular secretion
- Diffusion (non-ionic)
- Protein-binding
How are weak acid drugs eliminated?
Actively secreted into PCT
What is the effect of impaired renal function on drug therapy?
- Toxicity - drug not excreted and reaches toxic levels
2. Ineffective treatment - e.g. UTI antibiotic not reaching place of action
Define loading dose
A loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose
How is kidney function measured? What is taken into account?
eGFR MDRD formula - age - female - black ethnicity - creatinine
Define trough concentration
Trough concentration is the lowest concentration reached by a drug before the next dose is administered, often used in therapeutic drug monitoring.
What happens if you increase dose interval?
Decrease trough concentration
What happens if you decrease drug dosage?
Decrease peak concentration
How are opioids and their metabolites excreted?
Renally
What kind of drug an gentamicin? What effect does it have on the kidney
Aminoglycoside
Antibiotics
Causes nephrotoxicity and make kidney function worse
How do ACEi work?
And what is their outcome?
Decrease Ang II
Cannot vasoconstrict efferent arteriole to maintain glomerular capillary pressure
- decrease kidney function in setting of hypovolaemia
What do NSAIDs do with respect to kidney function?
Inhibit prostaglandins
- afferent arteriole dilation
What is the main effect of diuretics?
Increase urine volume
- Natriuresis (Na+ excretion) + water.
List the different types of diuretics and where they act
- Loop diuretics inhibit NKCC on TALH
- E.g.: Furosemide and bumetanide
- Most powerful diuretics, account for 15% - Thiazides inhibit Na/Cl co-transporter (NCC) on DCT
- E.g.: bendro-flu-methi-azide and hydrochloro-thiazide
- Better tolerated than loop diuretics but are less powerful - K-Sparing inhibit Na+/K+-ATPase pump on DCT/CD
- E.g. Spironolactone and eplerenone
- limited action, account for only 2% - Aldosterone antagonists inhibit aldosterone receptors and in turn blocking ENaC on CD. Also act on DCT
- Decrease potassium excretion (can be used in hypokalaemia)
- E.g.: Amiloride
Which is the most powerful diuretic?
Loop diuretic
E.g. furosemide
Which diuretic inhibits NKCC?
Loop diuretic
E.g. furosemide
Which diuretic inhibits Na+/K+-ATPase?
K-sparing
e.g. spironolctone
Which drug indirectly acts to reduced ENaC Action
Amiloride
Aldosterone antagonist
Which diuretic can help retain potassium
K-sparing diuretics
or
Amerloride
Where do thiazides work?
DCT inhibit NCC (Na/Cl co-transporters)
Give 2 examples of thiazide drugs
Hydrochlorothiazide
Bendroflumethithiazide
Give 2 examples of loop diuretics
Furosemide
Bumetanide
Give 2 examples of K-sparing diuretics
Spironolactone
eplerenone
Give 2 common conditions where you would prescribe a diuretic
Oedema
Hypertension
Which diuretic cannot be prescribed in kidney dysfunction?
K-sparing
Patient already cannot excrete adequate K+
= risk of hyperkalaemia
Which diuretic is best prescribed to kidney dysfunction patients?
Loop diuretics
Which diuretic carries risk of ototoxicity at high doses?
Loop diuretics
Where do spironolactones act?
K-sparing drugs
- MR antagonist
Which diuretic can be useful for hyperaldosterone states?
Aldosterone = mineralocoritoid
Use spironolactone to inhibit MR
How does amiloride work?
Blocks ENaC in CD
