renal 5 Flashcards
what is nephrotoxic drug
a drug that has potential to damage the kidney
when a patient has CKD/AKI what do you need to consider - the medication review
- stop the drug?
- withhold the drug?
- amend the dose?
- continue the drug?
how can kidney failure affect absorption
Patients with renal failure typically have oedema as their kidneys are less efficient at removing water and salt
Oedema can affect the wall of the bowel
This may lead to reduced absorption of drugs
how can kidney failure affect distribution
Drug distribution may also be affected by water balance
Oedema increased/dehydration will affect drugs that are more hydrophilic
Nephrotic syndrome leads to decreased protein levels in the blood. Many drugs are bound to proteins when in the blood. Lack of proteins will mean higher levels of free drug in the blood leading to toxicity e.g. phenytoin
how can kidney failure affect metabolism
Kidneys have a role in the metabolism of many drugs
Kidney failure means that these drugs will no longer be metabolised by the kidneys e.g. vitamin D
Uraemia can also reduce liver function leading to decreased metabolism of drugs
how can kidney failure affect excretion
Reduced renal clearance means increased levels of drugs or their metabolites in the blood
MDRD or Cockroft and Gault equations can be used to estimated kidney function
This value can be used to decide whether a drug should be suspended or a dose reduced
Useful resources = BNF/BNFC, SPC or Renal Drug Handbook
Cockroft & Gault = F x (140-age) x weight (kg) / serum creatinine
F = 1.04 for females and 1.23 for males
what are the nephrotoxic drugs?
CANDA Contrast media ACE Inhibitors NSAIDs Diuretics ARB’s
what makes contrast media nephrotoxic?
Contract induced nephropathy
Can occur in any patient with intra venous or intra-arterial contrast
Known renal dysfunction or CrCl = <60ml/min consider non-central imaging
Avoid in patients with renal failure!!
what makes ACE inhibitors nephrotoxic?
Used to treat hypertension, heart failure, nephropathy
Works on RAAS system inhibits conversion of angiotensin I to angiotensin II (lecture 1!)
Renal failure = reduced renal perfusion
ACEIs reduce blood pressure = worsening of renal failure (lecture 2!)
Hold in renal failure!!
NB. Renoprotective in CKD
If initiating in patients with CKD risk Vs benefit
what makes NSAIDs nephrotoxic?
Analgesic, antipyretic and anti-inflammatory
Non-selective COX inhibitors e.g. aspirin, ibuprofen, diclofenac, naproxen
Selective COX II inhibitors e.g. celecoxib
Inhibit prostaglandins = inhibits vasodilation of afferent arteriole = reduces kidney perfusion (lecture 2!)
PLUS promote sodium retention and therefore fluid retention
Hold in renal failure!!
where does ace inhibitor prevent constriction
afferent arteriole
aim of diruetics?
Diuretics cause diuresis “water tablets” take in the morning Primary aim to increase NaCl excretion and hence water excretion This can be achieved: - directly: by acting on the nephron - indirectly: by modifying the content of the filtrate The are various classes of diuretics (PLATO) - Potassium-sparing diuretics - Loop diuretics - Aldosterone antagonists - Thiazide or thiazide-like diuretics - Osmotic diuretics
what makes ARB nephrotoxic?
Blocks angiotensin ii
Renal failure = reduced renal perfusion
ACEIs reduce blood pressure = worsening of renal failure (lecture 2!)
Hold in renal failure!!
how can analgesic cause nephrotoxicity
Analgesics
- Opiates: reduced excretion = risk of accumulation = increased risk of side effects. Review dose! - Fentanyl and oxycodone = usually used in AKI/CKD
antibiotics - nephrotoxicity
avoid?
Antibiotics
- Aminoglycosides: gentamicin = avoid/reduce dose and follow guidelines - Glycopeptides: vancomycin = avoid/reduce dose and follow guidelines
