4. Excretion

Question 1

key ROUTES of ELIMINATION for many DRUGS

Answer 1

RENAL and BILIARY EXCRETION

Question 2

RENAL CLEARANCE consists of 3 processes

Answer 2

GLOMERULAR SECRETION

TUBULAR SECRETION

REABSORPTION

Question 3

GLOMERULAR FILTRATION of…

Answer 3

UNBOUND DRUG

only unbound drug filtered

Question 4

RENAL ABSORPTION OF..

Answer 4

LIPID SOLUBLE DRUGS

Question 5

for compounds that are NOT PROTEIN BOUND, NOT SECRETED or REABSORBED,
RENAL CLEARANCE approximates same as…

Answer 5

GFR
- GLOMERULAR FILTRATION RATE

Question 6

RENAL FILTRATION CLEARANCE of a PROTEIN-BOUND DRUG DEPENDS on the..

Answer 6

FREE FRACTION of drug in PLASMA (fu)

(cl filtration = fu x GFR)

Question 7

what does TUBULAR SECRETION involve

Answer 7

TRANSEPITHELIAL FLUX of DRUGS from BLOOD TO TUBULAR LUMEN

• ACTIVE process involving MULTIPLE TRANSPORTERS
• mainly in PCT of nephron

Question 8

when is TUBULAR SECRETION EVIDENT

Answer 8

when RENAL CLEARANCE of FREE FRUG EXCEEDS GFR

Question 9

what is REABSORPTION

Answer 9

TRANSEPITHELIAL BACK-FLUX of DRUG Molecules from lumen TO BLOOD

passive or active (transporters)

Question 10

PASSIVE REABSORPTION of which type of DRUGS

Answer 10

ONLY UNIONISED and NON-POLAR DRUGS with sufficient lipophilicity

Question 11

roughly what proportion of drugs eliminated at kidney - RENAL ELIMINATION

Answer 11

32%

Question 12

besides Genetics and patient characteristics, what also AFFECTS DRUG REABSORPTION and EXCRETION

Answer 12

URINE pH

because it determines the ionization state of a weak acid or base

and causes ability of drugs to acquire charges

Question 13

how is DRUG REABSORPTION as LOW pH (and excretion)

Answer 13

MORE REBASORBED
as MORE DRUG UNIONISED / UNCHARGED

• LESS EXCRETION

Question 14

how is DRUG CHARGE, REABSORPTION and EXCRETION at HIGH pH

Answer 14

MORE CHARGED

so LESS REABSORBED and MORE EXCRETED

Question 15

in ACIDIC URINE how is EXCRETION of WEAK ACID and WEAK BASES

Answer 15

LOWER excretion WEAK ACID

HIGHER excretion WEAK BASES

Question 16

in ALKALINE URINE how is EXCRETION of WEAK ACID and WEAK BASES

Answer 16

HIGHER Excretion WEAK ACIDS

LOWER excretion WEAK BASES

Question 17

RENAL FUNCTION usually determined by estimating the GFR by …. CLEARANCE

Answer 17

CREATININE CLEARANCE (CC)

Question 18

when might KIDNEYS have LOWER ABILITY to EXCRETE DRUGS

Answer 18

in CHRONIC KIDNEY DISEASE

Question 19

what is BILIARY EXCRETION

Answer 19

ACTIVE SECRETION of DRUG molecules or their metabolites from HEPATOCYTES INTO BILE

BILE then transported to GUT where drugs are EXCRETED

Question 20

in BILIARY EXCRETION, what in the GUT can cause metabolites DEGRADATION and DRUG REABSORPTION (enteric recirculation)

Answer 20

DECONJUGATING ENZYMES and GUT pH

Question 21

in BILIARY ELIMINATION where do the DRUGS go

Answer 21

INTO HEPATOCYTES
-> INTO BILE

(only small amount)

Question 22

what may require DRUG DOSE ADJUSTMENT

Answer 22

RENAL DISEASE