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GERR > Lecture 40: Drugs and the Kidney > Flashcards

Lecture 40: Drugs and the Kidney Flashcards

1
Q

outline the pharmacokinetics of penicillins

A
  • oral absorption variable
  • widely distributed in body fluids
  • mainly renal excretion (tubular secretion)
  • short plasma half life
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2
Q

how might penicillin dose be adjusted for Px w/ renal impairment

A
  • reduce dose delivery by extending period between each dose
  • still give same amount w/ each dose
  • (can also reduce dose amount but should check guidelines)
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3
Q

give an example of a drug that may be less effective in renal impairment and how this issue is resolved

A
  • thiazide diuretics less effective

- can use an alternative e.g. loop diuretics (cautiously)

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4
Q

give examples of drugs that can have more adverse effects in renal impairment

A

^ effect of drug:
- opioids/ sedatives

^ toxicity:

  • K+ sparing diuretics (hyperkalaemia)
  • metformin (lactic acidosis)
  • digoxin (arrhythmias/nausea)
  • nitrofurantoin (neuropathy)
  • tetracyclines (^ prot breakdown)
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5
Q

describe pre renal impairment in AKI and any pharmacological caution recommended in this case

A

pre renal impairment:
- dec. renal perfusion/ altered auto regulation, esp if sudden changes in volume state

caution:
- should discontinue potentially nephrotoxic drugs
- +/- support BP

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6
Q

give examples of drugs that can cause pre renal impairment

A
  • diuretics
  • antihypertensives
  • NSAIDs
  • ciclosporin (DMARD)
  • radio contrast media
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7
Q

give examples of drugs that can have an intrinsic effect on renal impairment

A
  • aminoglycosides (gentamicin)
  • amphotericin B
  • other antimicrobials (quinolone, macrolides)
  • anti platelets (clopidogrel)
  • anticonvulsants (carbamazepine, phenytoin)
  • DMARDs (ciclosporin, gold, penicillamine)
  • Lithium
  • NSAIDs / COX 2 inhibitors
  • radio contrast media
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8
Q

give examples of drugs that can cause post renal impairment

A

crystals/stones:

  • aciclovir
  • methotrexate

retroperitoneal fibrosis:

  • ergot derivatives
  • methyldopa/hydralazine/atenolol
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9
Q

what are the main drugs to look out for in Px w/ AKI

A
  • NSAIDs
  • ACEi/ARBs
  • diuretics
  • lithium
  • digoxin
  • gentamicin
  • methotrexate

DAMN = diuretics, ACEi/ARBs, methotrexate, NSAIDs

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10
Q

describe how NSAIDs -vely affect kidney

A
  • all cause nephrotoxicity
  • can cause:
  • -> acute tubular necrosis
  • -> interstitial nephritis
  • -> glomerulonephritis
  • -> renal papillary necrosis

(must ask about over the counter use)

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11
Q

describe how ACEi/ARBs affect kidney

A
  • complex relationship w/ renal impairment
  • can be used to control BP and reduce intraglomerular pressure, reducing proteinuria
  • may be assc. w/ deterioration of renal function and often need to be withheld when Px is acutely unwell
  • contraindicated in renal artery stenosis
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12
Q

describe diuretic drug interactions that affect kidney function

A
  • ^ electrolyte disturbances when combined w/ other diuretics
  • (loop) ^ oto and nephrotoxicity when combined w/ amino glycoside antibiotics
  • impaired renal diuresis when combined w/ NSAIDs
  • hypotension when combined w/ ACEi and other vasodilators
  • (thiazides) likely to cause lithium toxicity when co-prescribed
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13
Q

describe how lithium interacts w/ the kidney and any cautions

A
  • excreted by kidney
  • should be avoided in severe renal impairment
  • dose often needs reduced in episodes of illness as renal excretion of lithium reduced
  • can block effect of ADH on kidney –> diabetes insipidus
  • long term use can cause tubule-interstitial damage
  • risk of lithium toxicity ^ if co prescribed with diuretics/ACEi/ARBs
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14
Q

describe how digoxin interacts w/ kidney and any cautions

A
  • primary excreted by kidney and has narrow therapeutic range
  • half life and therefore time to steady state ^ as renal function dec.
  • risk of dig toxicity ^ by hypokalaemia so caution w/ diuretics (common co prescription in HF)
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15
Q

describe how gentamicin interacts w/ kidney

A
  • highly polar therefore IV admin
  • variable penetration into body fluids
  • eliminated by kidney T1/2 2-3hrs
  • elimination mirrors eGFR
  • nephrotoxic drug
  • must reduce dose and freq. in renal impairment to prevent dose dependent side effects
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16
Q

what is important when adjusting dose of gentamicin in renal impairment

A

need to measure trough levels and U+E more often

17
Q

what is important to remember when considering drug induced AKI

A
  • injury usually reversible if detected early
  • looking at serum creatinine and eGFR along w/ urinary sediment enables early detection
  • stop potentially nephrotoxic drugs
  • ensure appropriate supportive treatment e.g. IV fluids
18
Q

describe the changes that should be made when prescribing a drug in renal impairment

A
  • no change in loading dose of drug is required since volume of distribution is unaltered
  • for drugs eliminated by kidney dose should be reduced in Px w/ significant renal impairment
  • can be achieved by individual dose reduction or lengthening dose interval
  • maintenance dose reduction is required for drugs which are primarily eliminated by kidney and have a narrow therapeutic index
  • adjustment of dosage is usually achieved using eGFR (CrCl) or serum creatinine (less accurate)
19
Q

what are the principles for prescribing drugs in renal failure

A
  • for many drugs w/ only minor or no dose related side effects a simple scheme for dose reduction is sufficient
  • reduce the dose of drugs eliminated by kidney as time taken to reach steady state will be increased
  • avoid drugs which are nephrotoxic
  • adjustment of maintenance dose should be made using GFR and where appropriate plasma drug levels
20
Q

outline some treatment options in severe CKD

A
  • phosphate binding agents –> calcium carbonate taken w/ meals
  • in 2nd hyperPTH/ renal osteodystrophy –> 1,25-OH vit D (calcitrol) daily tablet
  • if symptomatic anaemia –> specialist may use erythropoietins
  • dialysis/ renal replacement therapy
21
Q

describe the effect of dialysis on drug dosage and clearance

A
  • solutes diffuse from blood into dialysis fluid
  • drugs that are small molecules w/ low protein binding will be removed readily
  • clearance of drugs may necessitate supplementary doses of drug e.g.
  • -> theophylline
  • -> metronidazole
  • -> gentamicin/tobramicin
  • -> antivirals
22
Q

when else might dialysis be used other than severe CKD

A

certain acute poisoning (dictated by how readily drug molecule can diffuse across) e.g.

  • aspirin
  • lithium
  • ethylene glycol
  • methanol
  • sodium valproate

GERR (46 decks)

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