Drugs and the Kidneys

Question 1

Which three processes are involved in renal excretion of drugs?

Answer 1

Glomerular filtration

Active tubular secretion

Passive tubular reabsorption

Question 2

Name a few mechanisms of which orally administered drug’s absorption may be reduced

Answer 2

Nausea, vomiting, diarrhoea
- associated with uraemia

Hypoproteinaemic oedema of GI tract
- e.g. nephrotic syndrome

Reduced intestinal motility and gastric emptying time
- uraemic nephropathy

Coadministeration of chelating agents
- e.g. phosphate binders

Question 3

Which two mechanisms affect the distribution of drugs

Answer 3

Changes in hydration state of patient

Alterations in protein binding
- due to hypoalbuminaemia, uraemia

Question 4

Why can metabolism be affected in renally-excreted drugs?

Answer 4

If metabolism is slowed due to , e.g. CKD, serum concentrations of parent drug are increased

Leads to drug toxicity and adverse effects

Question 5

How is elimination of drugs affected in renal impairment?

Answer 5

All three renal functions are reduced

Question 6

Why must opiates be used with extreme caution in patients with impaired renal function?

Answer 6

Potential accumulation of opiate metabolites due to significant increase in opiate half life

Question 7

What are the effects of uraemia in relation to medications?

Answer 7

Increased sensitivity to drugs acting on CNS e.g. benzodiazepines

Increased risk of GI bleed, e.g. NSAIDs

Increased risk of hyperkalaemia, e.g. K+-sparing agents

Question 8

Drugs that can cause hyperkalaemia?

Answer 8

ACE inhibitors
Angiotensin II receptor blockers
Spironolactone
Amiloride
NSAIDs
Potassium supplements

Question 9

Drugs that can cause hypokalaemia?

Answer 9

Loop diuretics - furosemide, bumetanide

Thiazide diuretics - bendroflumethiazide

Question 10

Name a drug that can cause lactic acidosis?

Answer 10

Meformin

Question 11

Name two drugs that a nephrotoxic which are used in renal graft anti-rejection?

Answer 11

Tacrolimus

Ciclosporin