Lecture 40 Drugs Of The Kidney Flashcards
Ways to alter drug dosage in renal impairment
Lengthen the time between administration
Check for the presence of thr drug in the body and wait for it to be at a low enough level in order to avoid overdosage
Drugs which ↑ efffect in renal impairment
Opioids
Drugs with Increased toxicity in renal impairment
Digoxin (anti arithmetic) may cause arrythmias and nausea
K+ sparing diuretics (cause hyperkalaemia) already ↑ K+ in renal impairment
Nitrofurantoin (neuropathy)
Tetracyclines (↑ protein breakdown)
Metformin (lactic acidosis)
Acute Kidney injury caused by pre renal impairment
↓ flow to the kidneys
↓ pressure in arterioles
Less filtration
Causes of pre renal impairment
Sudden changes in blood volume
Bleeding/vomiting/diarrhoea
Cardiac failure
Cirrhosis- low albumin and fluid into abdomen
What to do pharmacologically in acute kidney injury
Discontinue potentially nephrotic drugs and support blood pressure +/-
Drugs associated with pre renal impairment
Diuretics- ↓ blood volume Antihypertensives- ↓ blood flow | RAAS blocked so renin cannot regulate blood pressure NSAIDS- peripheral oedema Ciclosporin Radio contrast media
Post renal impairment causes
Blockage of drainage, bladder not able to be emptied
Due to
Crystals or stones
- aciclovir
- methotrexate
Retroperitoneal fibrosis
- ergot derivatives
- atenolol/hydralazine/methyldopa
STOP THE DAMN DRUGS
Diuretics
ACE inhibitors/ARBs
Metformin
NSAIDS
As well as, Lithium Digoxin Gentamicin Methotrexate
NSAIDS in AKI
Discontinue- cause nephrotoxicity
Ask about OTC use
Can cause interstitial nephritis
ACE inhibitors and ARB in AKI
Can help in hypertension of the glmoerlous which causes damage
But stop as it can cause HYPOtension= ↓ renal blood flow= ↓ function= AKI
When to discontinue ACE and ARB in AKI
DONT use in
Renal artery stenosis
Hypofiltration
Use in
Hyperfiltration
Diuretic drug interactions AKI
↑ nephrotoxicity when combined with aminoglycocides
Impaired diuresis when combined with NSAIDs
Hypotension when paired with ACE inhibitors and other vasodilator drugs
Cause lithium toxicity when co prescribed
Drugs not to prescribe with diuretics in AKI
Amioglycosides
NSAIDs
ACE inhibitors
Lithium
Lithium in AKI
Excreted in the kidney
Avoided in severe renal impairment
Long term use can cause tubulo-interstitial damage
Can block the effects of ADH causing diabetes incipidous
Lithium toxicity if prescribed with
- diuretic
-Ace inhibitors
Diabetes incipidous
Salt excretion in the urine
Bitter urine
Digoxin in AKI
Used in atrial fibrillation
Primarily excreted in the kidney
Risk of toxicity because of ↑ half-life due to ↓ excretion in kidney damage
Toxicity ↑ by hypokalemia= caution with diuretics
Gentamicin in AKI
Eliminated by the kidneys
Antibiotic for gram -ve bacteria
Result in AKI
- less excretion of gentamicin
- if dose not ↓, leads to toxicity and liver disease
What we must do with gentamicin if renal impairment
Reduce dose
Reduce frequency
To prevent dose dependent side effects
Check levels using the trough levels
Urea and electrolytes measurement of gentamicin excretion
AKI, what to look at and what to do
Look at eGFR and serum creatinine and urinary sediment
Stop nephrotic drugs
Supportive treatment (IV Fliuds)
What happens in kidney failure
Salt, fluid and nitrogenous compounds not filtered or excreted, buildup of substances in the body which may be toxic
Ie. H+ ions, urea, ammonia, drugs
Renal impairment, what to do with dosage of drugs
Loading dose stays the same to get to the therapeutic range quickly
↓ maintenance dose in drugs eliminated by the kidneys
a) individual dose reduction
b) lengthen dose interval
How is adjustment of the dose worked out
eGFR (creatinine clearance)
Serum creatinine
Principles of prescribing in renal failure
Reduce dose of drugs eliminated by kidneys
(Due to the time taken to reach steady state will be ↑)
Avoid drugs which are nephrotixic
Adjust maintenance dose using GFR or plasma drug levels
