Basic Principles VI

Question 1

renal excretion

Answer 1

most important route of elimination of drug or metabolites

Question 2

glomerular filtration

Answer 2

only free drug molecules are filtered. amount filtered depends on glomerular blood flow and free drug concentration

Question 3

amount of drug excreted formula

Answer 3

amount of drug excreted = amt entering tubule - amt reabsorbed

Question 4

active tubular secretion

Answer 4

active transport, one system for acids and one for bases. exists for endogenous compounds like uric acid or choline. inhibition is usually competitive. saturation can occur at therapeutic doses or with overdoses. changes first order processes to 0 order

Question 5

first order equation

Answer 5

v = Vmax[D]/km+[D]

Question 6

0 order equation

Answer 6

v = Vmax[D]/[D]

Question 7

passive reabsorption

Answer 7

especially common in lipid soluble drugs. after free water absorption, these are concentrated in the loop of henle. reverse concentration gradient occurs

Question 8

active reabsorption

Answer 8

active transport for endogenous compounds, works for some drugs

Question 9

amount of drug excreted formula factoring in reabsorption

Answer 9

amt of drug excreted = (glomerular filtration + active tubular secretion) - (passive reabsorption + active reabsorption)

Question 10

how to enhance renal excretion?

Answer 10

forced diuresis by increasing urine volume, or manipulate the pH of the urine, trapping the ionized drug. increase the pH of the urine!

Question 11

biliary excretion

Answer 11

enter bile by secretion (active transport system) or passive diffusion. reabsorbed by passive diffusion and the original absorption mechanism. cycling can occur.

Question 12

other routes of elimination

Answer 12

lung (exhaled air), sweat, saliva, tears, breast milk

Question 13

elimination of drugs from site of action

Answer 13

decreases the concentration in the plasma

Question 14

clearance

Answer 14

a combination of biotransformation and excretion. contribution of each process will vary for different drugs. a volume of plasma that is cleared of drug per unit of time (ml/min)

Question 15

clearance total =

Answer 15

clearance metabolic + clearance renal. in hepatic diseases, metabolic clearance is reduced. in renal disease, renal clearance is reduced.

Question 16

factors influencing clearance

Answer 16

body surface area, protein binding, cardiac output, renal function, hepatic function, blood flow to systemic organs

Question 17

alpha part of the elimination curve

Answer 17

distribution

Question 18

beta part of the elimination curve

Answer 18

elimination

Question 19

what is Ke determined by?

Answer 19

the rate limiting step in clearance. either metabolic or renal

Question 20

absorption kinetics

Answer 20

helps us understand how much dose to give. absorption rates are related to the transport processes involved, either zero order or first order. first order are sensitive to drug concentration, while 0 order are saturated

Question 21

zero order absorption rate formula

Answer 21

Ct = k t

an amount asorbed per unit time. Ct = concentration of a drug. T is time, and k is constant

Question 22

first order absorption rate formula

Answer 22

Ct = M/Vd (1-e^-kt)

M = amount of drug at site

Question 23

elimination kinetics

Answer 23

helps us understand how often to give a dose

Question 24

zero order elimination formula

Answer 24

Ct = Co -KeT

Ke is elimination constant, Co is initial conentration, Ct is concentration at time T

Question 25

first order elimination formula

Answer 25

log Ct = log Co - KeT/2.303

Question 26

when can something switch from a first order to a zero order?

Answer 26

when concentration is higher than the constant, it is a 0 order

Question 27

what has half lives? which order reaction

Answer 27

first order only have half lives

Question 28

formula for half lives

Answer 28

t1/2 = 0.693/Ke

Question 29

clearance formula involving distribution and elimination

Answer 29

Cl = Vd x Ke

t1/2 = 0.693Vd / Cl