Prescribing in Renal disease

Question 1

What are patients with renal (or hepatic disease) less able to do with drugs?

Answer 1

metabolise or excrete them

Question 2

What is the cycle of prescribing issues in renal disease?

Answer 2

pts with renal problems are less able to metabolise/excrete them but then …
drugs also commonly cause hepatic or renal impairment

Question 3

some drugs are not effective for patients with renal impairment what are 2 common examples?

Answer 3

nitrofurantoin / trimethoprim

urine infection

Question 4

What are the dangers of prescribing in renal impairment?

Answer 4

reduced renal excretion of a drug of metabolites could increase risk of adverse reations
drug sensitivity is increased even if elimination is unimpaired
nephrotoxic drug side effects
some drugs are less effective

Question 5

what common drugs are nephrotoxic?

Answer 5

aminoglycosides
diuretics
ace inhibitors/ARBs
NSAIDs

Question 6

How do ACE inhibitors, ARB and aldosterone antagonists cause increased sensitivity to side effects in renal impaired patients?

Answer 6

they cause hyperkalaemia

Question 7

what other drugs cause increased sensitivity to side effects?

Answer 7

anticoagulants e.g. rivaroxaban
antacids
NSAIDs

Question 8

Which drugs need dose reduction in renal impairment?

Answer 8

digoxin
DM meds: metformin, sulphonylureas, insulin
many antimicrobials: penicillin, cepalosporin, vanc, antifungals
heparin
opioids

Question 9

What can i do as a prescriber about prescribing drugs for renally impaired patients?

Answer 9

think of it - check the drug (BNF) and check pts renal function
avoid it - use alternative drug, use AS FEW as possible
minimise harm - use low dose, monitor appropriately (side effects, renal function, drug concentrations), stop drugs

Question 10

How do NSAIDs cause renal harm?

Answer 10

NSAIDs -
PGs help preserve renal blood flow in cases of AKI due to effective volume depletion (HF, salt & water losses) by vasodilating the afferent arteriole…
NSAIDs inhibit PG synthesis ==> afferent vasoconstriction => reduced GFR

Question 11

Hoe do ACEI’s affect kidneys?

Answer 11

again (like NSAIDs) they cause reduced GFR/AKI in states of effective volume depletion/renal failure
Angiotensin-induced VC of efferent arteriole maintains GFR in chronic renal impairment, HF and bilateral renal artery stenosis ==> check renal function w/i 1xWeek of starting ACEI
ACEi also = hyperkalaemia because normally the RAAS system stimulates aldosterone sensing high K+ = inc urinary K+ excretion

Question 12

How do aminoglycosides affect kidney function?

Answer 12

they cause AKI due to tubular necrosis (10-20% patients)

so avoid in pts at risk of AKIs

Question 13

How does iodinated contrast affect kidneys?

Answer 13

they pose an AKI risk via vasoconstriction and direct cytotoxicity - avoid in at-risk patients

Question 14

How does gadolinium MRI contrast affect kidneys?

Answer 14

causes nephrogenic systemic fibrosis - a disorder seen in pts with renal impairment & recent exposure to gadolinium

Question 15

how do NSAIDs, gold and penicillamine cause nephrotic syndrome?

Answer 15

NB penicillamine = cystinuria, RA and metal poisoning Rx
NSAIDs –> minimal change disease
gold & penicillamine –> membranous nephropathy

Question 16

What do these drugs cause:

nsaids, penicillins, allopurinol, PPIs, 5-aminosalicylates e.g. mesalazine [IBD Rx}

Answer 16

acute tubulointerstitial nephirits

Question 17

chemotherapy and antiretrovirals e.g. tenofovir cause tubular disorders in the kidney. What condition can tenofovir cause?

Answer 17

tenofovir –> proximal tubular dysfunction –> fanconi syndrome
= where glucose, AA, bicarb and phosphate, uric acid and K is not reabsorbed by proximal tubule (–> urine)