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GERR > Drugs and the kidneys > Flashcards

Drugs and the kidneys Flashcards

1
Q

What is the relation between half life of a drug and clearance rate?

A
  • half life and clearance rate inversely proportional

- clearance rate lowered if renal impairment

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2
Q

What is the most common drug given in patients with sepsis?

A

Tazocin (piperacillin/tazobactam)

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3
Q

How does drug dosing change in patients with renal impairment?

A

Either:

  • Give less frequently
  • Or give lower dose
  • Either way as half life of the drug will be extended due to impairment reduces overdosing
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4
Q

Which drugs are less effective in renal impairment due to effects on pharmacodynamics?

A
  • Thiazide diuretics give loop instead

- Nitrofurantoin (antibiotic used for UTIs) give trimethoprim instead

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5
Q

Which drugs will produce more adverse effects in renal impairment?

A
  • opioids/sedatives (will have an increased effect)
  • Digoxin (arrhythmias/nausea)
  • K+ sparing diuretics (Hyperkalemia)
  • Nitrofurantoin (neuropathy)
  • Tetracyclines (protein breakdown)
  • Metformin (lactic acidosis)
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6
Q

What is the most common form of acute kidney injury?

A
  • Pre-renal impairment

- change in BF going into the kidney

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7
Q

What are the types of AKI?

A
  • decreased renal perfusion

- Altered auto regulation

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8
Q

What are the causes of acute kidney injury?

A
  • vomiting/diarrhoea
  • bleeding
  • cardiac failure
  • cirrhosis
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9
Q

What are the most important first steps in treating AKI?

A
  • Discontinue nephrotoxic drugs
  • Manage BP
  • Supportive treatment usually IV fluids
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10
Q

Why does cirrhosis cause AKI?

A
  • liver failure leads to low albumin
  • can’t make proteins as so get fluid loss into abdominal cavity and peripheries (peripheral oedema)
  • loss of volume from systemic system
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11
Q

What drugs can cause AKI by reducing BF?

A
  • Diuretics (due to loss of fluid)
  • antihypertensives e.g. ACE inhibitors, ARBs, (due to blocking of RAAS) CCBs and nitrates (exacerbate any problems of low BP)
  • NSAIDs (cause peripheral oedema)
  • Ciclosporin
  • Radio contrast media (used in CAT/CT scan)
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12
Q

Why does fluid loss cause AKI?

A

Fluid loss means reduction in blood volume which means reduction in BP and so worse BF to kidney

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13
Q

Drugs which cause intrinisic renal impairment?

A
  • Aminoglycosides
  • Amphotericin B
  • other Antimicrobials
  • Anti-platelets
  • Anti-convulsants
  • DMARDs
  • Lithium
  • NSAIDs/COX-2 inhibitors
  • Radio contrast media
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14
Q

Drugs causing post - renal impairment (not very important as usually caused by larger blockage)

A
  • Aciclovir and methotrexate (Cause crystals/stones)

- Ergot derivaties and methyldopa/hydralazine/atenolol (Cause Retroperitoneal fibrosis)

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15
Q

What are the most important drugs to look out for in patients with AKI (stop use of these drug)

A 
(DAMN drugs) 
Diuretics 
Digoxin
ACE-I/ARBs
Methotrexate 
NSAIDs
Lithium 
Gentamicin
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16
Q

Why do NSAIDS need to be stopped in patients with AKI?

A
  • Nephrotoxic

- mainly due to interstitial nephritis and can also cause necrosis of tubules and glomerular nephritis

17
Q

When are ACE-I/ARBs useful in patients with kidney damage?

A
  • Reduces hyperfiltration by controlling BP of afferent arteriole
  • usually occurs in diabetes
  • means reduction in proteinuria
18
Q

When do ACE-I/ARBs cause further kidney damage to patients?

A
  • patients with AKI
  • BF already reduced so hypo filtration
  • Drugs will worsen this as block RAAS
  • RAAS is designed to increase BF/BP
  • always contraindicated in Renal artery stenosis
  • if on ACE/ARB and start feeling unwell stop drug and wait a few days
19
Q

Why are diuretics contraindicated in patients with AKI?

A

Will further reduce blood volume and so blood flow to the kidney

20
Q

What are the diuretic drug interactions?

A
  • Diuretic + diuretic can increase electrolyte disturbances
  • amino glycoside antibiotics further increase nephrotoxicity
  • impaired diuresis with NSAIDs
  • Cause hypotension when with ACE-I and the vasodilators
  • with Lithium cause lithium toxicity when co-prescribed thiazides
21
Q

Why is lithium avoided in patients with AKI?

A
  • excreted by the kidneys
  • dose needs reducing when ill as renal excretion of lithium reduced
  • over time lithium will block effects of ADH (can diabetes insipidus where difficulty concentrating urine as excrete too much salt)
  • get tubule-interstitial damage
22
Q

Why is Digoxin contraindicate din patients with AKI?

A
  • completely dependant on kidneys for clearance and very small therapeutic range
  • so changes in kidney function will have massive effects
  • risk of toxicity also increased by hypokalemia so caution with diuretics
23
Q

Why is gentamicin contraindicated?

A
  • elimination completely dependant on kidney
  • nephrotoxic also so accumulation when not eliminated will cause further damage
  • dose and frequency reduced in patients with renal impairment
  • When dosing very important to keep checking trough levels and U+E
24
Q

Is AKI reversible?

A

Yes if detected early

25
Q

What tests should be done to assess AKI?

A
  • Serum creatinine
  • eGFR
  • Urinary sediment
26
Q

What are the stages of CKD?

A

1) >90
2) 80-89
3A) 45-59
3B) 30-44
4) 15-29
5) <15 Kidney failure

27
Q

When would you qualify for kidney transplant or dialysis?

A

Stage 4

Stage 5 kidney no longer viable would need dialysis or transplant

28
Q

How does renal impairment impact drug elimination?

A
  • No affect on loading dose as doesn’t change volume of distribution
  • Maintenance dose will need to be reduced by reducing individual dose or lengthening dose interval
  • adjust dose based on eGFR levels and serum creatinine
29
Q

What drugs will need to be given in patients with stage 5 CKD?

A
  • phosphate binding agents (calcium carbonate with meals)
  • Get secondary hyperPTH / renal osteodystrophy so need to take calcitriol daily
  • symptomatic anaemia give erythropoetin
  • Put on dialysis
30
Q

What is dialysis?

A
  • blood taken from systemic system out through artificial filtration system
  • filtration system will remove small molecules with low protein binding more readily and clear drugs
  • drug dose may therefore need to be increased
31
Q

What drugs will need to have increased doses in patients on dialysis?

A
  • Theophylline
  • Metronidazole
  • Gentamicin
  • Anti-virals
32
Q

For which drugs can dialysis be used to treat acute poisoning?

A
  • Aspirin
  • Lithium
  • ethylene glycol
  • Methanol
  • Sodium valproate
33
Q

What equation is used to calculate how quickly the drug will be eliminated?

A

5 x half life

GERR (49 decks)

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