Renal/kidney Drug Excretion

Question 1

Which drugs are reabsorbed at the kidney to become more polar for excretion

Answer 1

Lipid soluble

Question 2

Which 3 processes in renal excretion are involved in drug excretion

Answer 2

Glomerular filtration

Tubular reabsorption (loop of henle)

Tubular secretion (collecting duct)

Question 3

Only a small amount of drugs don’t pass through glomerulus, which ones and why

Answer 3

Protein bound drugs such as warfarin or heparin

Bound to albumin which stays in plasma (too large)

Question 4

What happens in active tubular secretion

Answer 4

Drugs transferred from capillaries to the tubular lumen actively against electrochemical gradient

Question 5

What 2 carrier pathways are there in drug tubular secretion into tubular lumen

Answer 5

Acidic drugs = 1 pathway

Neutral and basic drugs = second pathway

Question 6

Which process happens in tubular reabsorption (loop of henle)

Answer 6

Diffusion

Question 7

When water is reabsorbed back into capillaries which drug stays in the plasma conc

Answer 7

Lipid soluble - don’t get excreted

Question 8

Which drug is excreted due to conc gradient

Answer 8

Water soluble

Question 9

What 2 variables does reabsorption depend on

Answer 9

Pka of drug

Ph

Question 10

Which drug is excreted if the tubular fluid is alkaline

Answer 10

Acidic drugs because they are acidic so can’t be reabsorbed

Question 11

When is a drug 50% ionised (equal conjugate base to acid)

Answer 11

When the Pka is same as Ph

Question 12

What happens if ph is higher than pka

Answer 12

More is ionised

Question 13

Why is ph and pka used to allow either reabsorption or excretion tailoring

Answer 13

Something can be added to the renal fluid which either traps the drug so can’t be reabsorbed so is excreted or it can be reabsorbed into capillaries