Lecture 40 Drugs Of The Kidney

Question 1

Ways to alter drug dosage in renal impairment

Answer 1

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

Question 2

Drugs which ↑ efffect in renal impairment

Answer 2

Opioids

Question 3

Drugs with Increased toxicity in renal impairment

Answer 3

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)

Question 4

Acute Kidney injury caused by pre renal impairment

Answer 4

↓ flow to the kidneys
↓ pressure in arterioles
Less filtration

Question 5

Causes of pre renal impairment

Answer 5

Sudden changes in blood volume
Bleeding/vomiting/diarrhoea
Cardiac failure
Cirrhosis- low albumin and fluid into abdomen

Question 6

What to do pharmacologically in acute kidney injury

Answer 6

Discontinue potentially nephrotic drugs and support blood pressure +/-

Question 7

Drugs associated with pre renal impairment

Answer 7

Diuretics- ↓ blood volume 
Antihypertensives- ↓ blood flow | RAAS blocked so renin cannot regulate blood pressure 
NSAIDS- peripheral oedema 
Ciclosporin
Radio contrast media

Question 8

Post renal impairment causes

Answer 8

Blockage of drainage, bladder not able to be emptied

Due to
Crystals or stones
- aciclovir
- methotrexate

Retroperitoneal fibrosis

• ergot derivatives
• atenolol/hydralazine/methyldopa

Question 9

STOP THE DAMN DRUGS

Answer 9

Diuretics
ACE inhibitors/ARBs
Metformin
NSAIDS

As well as,
Lithium 
Digoxin 
Gentamicin 
Methotrexate

Question 10

NSAIDS in AKI

Answer 10

Discontinue- cause nephrotoxicity
Ask about OTC use
Can cause interstitial nephritis

Question 11

ACE inhibitors and ARB in AKI

Answer 11

Can help in hypertension of the glmoerlous which causes damage
But stop as it can cause HYPOtension= ↓ renal blood flow= ↓ function= AKI

Question 12

When to discontinue ACE and ARB in AKI

Answer 12

DONT use in
Renal artery stenosis
Hypofiltration

Use in
Hyperfiltration

Question 13

Diuretic drug interactions AKI

Answer 13

↑ 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

Question 14

Drugs not to prescribe with diuretics in AKI

Answer 14

Amioglycosides
NSAIDs
ACE inhibitors
Lithium

Question 15

Lithium in AKI

Answer 15

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

Question 16

Diabetes incipidous

Answer 16

Salt excretion in the urine

Bitter urine

Question 17

Digoxin in AKI

Answer 17

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

Question 18

Gentamicin in AKI

Answer 18

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

Question 19

What we must do with gentamicin if renal impairment

Answer 19

Reduce dose
Reduce frequency
To prevent dose dependent side effects

Check levels using the trough levels
Urea and electrolytes measurement of gentamicin excretion

Question 20

AKI, what to look at and what to do

Answer 20

Look at eGFR and serum creatinine and urinary sediment
Stop nephrotic drugs
Supportive treatment (IV Fliuds)

Question 21

What happens in kidney failure

Answer 21

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

Question 22

Renal impairment, what to do with dosage of drugs

Answer 22

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

Question 23

How is adjustment of the dose worked out

Answer 23

eGFR (creatinine clearance)

Serum creatinine

Question 24

Principles of prescribing in renal failure

Answer 24

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

Question 25

Other renal activities (blood production)

Answer 25

Kidneys produce EPO
EPO stimulates RBC production in marrow
↑ blood cells

Question 26

Other renal activities (vitamin d)

Answer 26

Parathyroid hormone stimulates Ca2+ uptake

Activated vitamin D released from kidneys

Question 27

What Happens in severe CKD

• calcium
• blood

Answer 27

Calcium

• vitamin d doesn’t get activated in kidneys
• Ca2+ levels fall
• PTH ↑ secretion
• hyperparathyroidism = bone thinning (osteodystrophy)

Treated with activated vitamin d tablet (calcitriol)

Blood
- ↓ EPO production due to ↓ renal function
- ↓ blood production stimulation
= anaemia

Treatment- dialysis/renal replacement therapy

Question 28

Dialysis

Answer 28

Solutes diffuse from blood into dialysis fluid

• small molecule drugs with low protein binding will be removed
• clearance of drugs may= more drugs

Question 29

Dialysis in acute poisoning

Answer 29

Can be used in some drugs depending on how easy it is for the drug to diffuse across

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