Issar- Drug Excretion

Question 1

bowmans capsule is very porous for filtration. so will drug bound to a protein be filtered thru here?

Answer 1

no. because it is to big

Question 2

active tubular secretion occurs in the proximal tubule. since it is a an active process, what may occur?

Answer 2

competitve inhibition of the secretion of one compound by another (ex. penicillin competes with probenecid, which is a gout drug)

Question 3

what is used to measure renal clearance?

Answer 3

inulin

Question 4

in order to get reabsorbed what must the non-ionized form have a sufficient amount of?

Answer 4

lipophilicity

Question 5

what is the equaiton for rate in= rate out?

Answer 5

(CLr)(Cp)=(Qu)(Cu)

Question 6

if a drug is only partially reabsorbed what is the clearance drug: clearance inulin ration?

Answer 6

ratio<1

Question 7

if the ratio, CLdrug: CLinulin > 1. what is the probable mechanism of renal excretion?

Answer 7

actively secreted

Question 8

what ratio is necessary for the drug to be only filtered?

Answer 8

CLdrug: CLinulin =1

Question 9

what is the equation for renal clearance?

Answer 9

CLr= (Qu*Cu)/ Cp

Question 10

if the renal clearance for a drug has decreased, what can be implied about the plasma concentration of that drug?

Answer 10

it has increased

Question 11

what type of excretion do strongly polar groups, and high m.w compounds go through? (m.w. more than 500)

Answer 11

biliary excretion

Question 12

enterohepatic circulation works to prolong the duration of action of certain drugs. how is this done?

Answer 12

creates reservoir of recirculating drug by becoming hydrolyzed in gut by beta-gluronidase - available for reabsorption

Question 13

what factors affect biliary secretion?

Answer 13

liver disease or injury, age, chronic administration of drugs increase bile flow, competition between drugs

Question 14

are highly soluble drugs faster at being removed via pulmonary excretion?

Answer 14

no. they are removed slower (NO is not very soluble in blood and is excreted rapidly)

Question 15

what is excretion in sweat and saliva dependent on?

Answer 15

diffusion of non-ionized form of drug

Question 16

in milk, the presence of drug is dependent on?

Answer 16

maternal blood concentration, plasma protein binding, lipid solubility and pKa

Question 17

what prevent toxic drugs from entering the CNS?

Answer 17

P-glycoprotein

Question 18

what is the overall renal excretion controlled by?

Answer 18

what happens in the tubules

Question 19

what drug is extensively secreted, with clearance values approaching the renal plasma flow rate of 425-650ml/min?

Answer 19

p-aminohippuric acid (PAH)

Question 20

what else besides inulin is used to estimate the GFR

Answer 20

creatinine - is freely filtered and not reabsorbed

Question 21

what does it mean if the plasma creatinine increases?

Answer 21

the Cl(creatinine) has decreased and kidney function has decreased

Question 22

what do drugs like quinidine, ketoconazole, and verapamil do to the drug digoxin?

Answer 22

they increase the serum concentration of digoxin by inhibiting activity of Pgp (requires Pgp for excretion)

Question 23

what do drugs like rifampin or St. John’s wart do to digoxin?

Answer 23

they decrease serum concentration by inducing Pgp activity