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Pharmcology > lecture 5 > Flashcards

lecture 5 Flashcards

1
Q

tissue perfusions 1 phase

A

-liver
-kidney
-brain

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2
Q

second distribution phase

A

muscle
viscera skin
fat (slower)

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3
Q

diffusion of the drug into the interstitial fluids

A

occur RAPID and because highly permeable nature of capillary endothelial membrane (except brain)

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4
Q

distribution

A

partitioning of drugs between BLOOD and the TISSUE

Determinants- transmembrane pH and the lipid solubility

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5
Q

tissue binding :

“depot” definition

A

drug is BOUND in tissue

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6
Q

True or false: Drugs in TISSUE are in higher concentrations than Drug in EXTRACELLULAR FLUID

A

true

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7
Q

example of slide 6: Quinacrine (anti-malaria)

A

conc in LIVER is several thousand more times than in BLOOD

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8
Q

TISSUE BINDING

A

occurs in cellular constituents - proteins, phospholipids, nuclear protein and are REVERISBLE

**CAN produce local toxicity, as in the case of “amino glycoside, antibiotic gentamicin” (in kidney)

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9
Q

amino-glycoside antibiotic gentamicin (in the kidney )

A

produces a local toxicity because of tissue binding or accumulation

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10
Q

many lipid soluble drugs are stored in

A

NEUTRAL FAT.

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11
Q

in obese people the fat content of the body is as high as

A

50%

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12
Q

bone

A

*tetracycline antibiotic
metal ion chelating agents and heavy metals can accumulate in the bone by absorption into the bone crystal surface and eventual incorporation into a crystal lattice.

Bone can be a reservoir for toxic agents- radium and lead in blood

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13
Q

Redistribution

A

Termination of drug effect- is done by metabolism, excretion, and redistribution.

redistribution of drugs from its site OF ACTION into OTHER SITES/TISSUE

  • specifically terminates highly lipid-soluble drug that acts on the brain or cardiovascular system (INJECTIONS /INHALATION)
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14
Q

bbb

A

lipid solubility, non-ionized, unbound

the drug should be very LIPOPHILIC - to cross the bbb

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15
Q

Distribution

A

Some barriers restrict flow into the CNS- BBB

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16
Q

BBB

A

the brain has capillaries that cannot seep between cells (paracellular transport), and must be transported transcellular.

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17
Q

choroid plexus

A

where the CSF is formed, and has a TIGHT JUNCTION BARRIER, epithelial in nature

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18
Q

what kind of drugs make it into the CNS ?

A

Lipid soluble and non-polar

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19
Q

Inflamed BBB

A

will enahcne the permeability

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20
Q

transport fro CSF to blood

A

ACTIVE TRANSPORT

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21
Q

BBB we can use it for drug design

A

to limit ACTION OF PERIPHERY

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22
Q

PLACENTAL TRANSFER

A

DRUGS TRANSFER TO THE FETUS
** Fetus plasma SLIGHTLY more acidic than mother, 7-7.2 compared to 7.4, ION TRAPPING OF BASIC DRUGS OCCURS

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23
Q

Volume of Distribution (Vd)

A

**APPARENT -measure
theoretical and practical significance

amount of drug in the body to the concentration of drug in plasma or blood.

Vd= amount of drug in the body (mg)/ conc mg/L

DOSE/ conc in blood (at steady state
mass/density-volume

Vd can EXCEED THE actual volume of biological system

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24
Q
A

If the volume of distribution (Vd) exceeds the actual volume of blood, it means that the drug is not confined solely to the bloodstream, but has distributed itself into tissues, organs, and other body compartments beyond the blood.

In this scenario, the drug is distributed throughout the body, not just in the bloodstream. This could mean that the drug has entered tissues, cells, or other compartments where it can exert its pharmacological effects or be metabolized and eliminated.
If the Vd is large, it suggests that the drug has a widespread distribution throughout the body and may have a longer duration of action or a larger area of effect.

This could be due to factors such as the drug’s molecular size, lipid solubility, binding to proteins or tissues, or other pharmacokinetic properties. A large Vd may also indicate that the drug is extensively distributed into tissues and organs, which can affect its pharmacokinetic profile and therapeutic efficacy

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25
Q

total body of water

A

0.6 L/kg

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26
Q

extracellular water

A

0.2 L/kg

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27
Q
A
28
Q

bone

A

0.07 L/kg

29
Q

blood

A

0.08 L/kg

30
Q

plasma

A

0.04 L/kg

31
Q

Fat

A

0.2-0.35 l/KG

32
Q

small water-soluble molecule

A

Ethanol- 37 L

33
Q

LARGE WATER SOLUBLE MOLECULES

A

gentamicin- 18L

34
Q

STRONG PLASMA protein bound molecule that is LARGE

A

heparin- 3.4 L

35
Q

highly lipid soluble molcules

A

DDT

36
Q

certain ions

A

fluoride

37
Q

Vd is large distribution

A

IS GREAT

38
Q

Vd is small distrution

A

LIMITED

39
Q

CLEARANCE

A

Ratio rate of elimination by GI LIVER AND KIDNEY/ CONCENTRATION in the fluid-like blood

renal is kidney
determine for RENAL and Liver, GI, Respiratory Sweat

40
Q

Cl=

A

rate of elimination/ conc

41
Q

RATE of elimination

A

Conc x Clearence

42
Q

total systemic clearance is

A

summing up all. the clearances of each process like Cl renal +Cl liver

43
Q

clearance

A

remains constant and FIRST-order kinetics

rate of drug removal/ conc

rate of removal: mg/ min
conc: mg/mL
clearance- ml/min

*clearance is the volume if fluid or blood that would need
to be completely free of all drugs to account for elimination

  • as the drug concentration of drug increase the rate of elimination will also increase
    BUT Clearance is remains sam
44
Q

variable clearance

A

is FIRST ORDER
*we can find clearance in a first oder by estimating the AUC

clearance= dose(conc(/ AUC

45
Q

Constant clearance

A

is zero order (clearance remains same as we increase CONC and elimination)

46
Q

main factors in renal excretion-1

A

glomerular filtration- tells us the fraction of free drugs compared to the protein-bound drug , when the drug is strongly bound to protein it DOES NOT FILITER

47
Q

main factors in renal excretion- passive tubular reabsorption

A

enhanced lipid solubility favors reabsorption, lipid-soluble readily cross renal tubular epithelial to enter pericappilary fluids

ex. thiopental, highly lipid soluble and completely reabsorbed and unchanged drug excreted in urine

48
Q

high concentration of drug causes

A

elimination to be saturated - called “capacity limited elimination”

49
Q

examples of capacity limited elimination

A

phenytoin, ethanol, aspirin

50
Q

capacity limited elimination

A

rate of elimination INDEPENDENT FROM CONC so the clearance will FALL

51
Q

OTHER NAMES FOR CAPACITY LIMITED ELIMINATION

A

conc/dose dependent (high conc)
saturable
non-linear
Michaelis menten kineitcs
elimination

52
Q

capacity limited kinetics

A

a constant amount of drug is eliminated per unit of time vs constant fraction of drug eliminated per unit of time

a state state conc cannot be reached

53
Q

rate of elimination

A

= vmax x c/ km + c

km- drug conc at which elimination half Vmax
vmax- max elimination capacity

54
Q

flow-dependent elimination

A

cleared rapidly by the organ (liver will metabolize drug completely)

clearance depends on blood flow (where the rate of drug delivery to the organ or liver)

high extraction drug

55
Q

neonates clearance

A

they have reduced hepatic metabolism and renal excretion, organ are immature still

56
Q

clearance elderly patients

A

differences in absorption, hepatic metabolism, renal clearance and vol distribution

57
Q

genetic factor-clearance

A

genetic polymorphism affects-

CYP….
2D6
2C19
2A6
2C9
N-acetyltransferase

which have significant differences in drug metabolism abilities

58
Q

half life

A

time interval after which conc is half at the beginning time interval

constant throughout the dosing interval or time interval observed

  • ONLY meaning in first order

time required to eliminate 1/2 of the total amount of drug in the body

usually the constant rate of elimination

one t 1/2 will reduce drug in the body by 50%

useful to identify steady states

Means for estimation of appropriate dosing interval

59
Q

1 half life - 6half lives

A

1-50
2-25
3-12.5
4-6.25
5-3.12
6-1.56

60
Q

approximately 4 half-lives are required to reach

A

about 94% of a new steady-state

61
Q

t1/2 = (0.693 · Vd)/CL

A

(0.693 · Vd)/CL

62
Q

Factors affecting t1/2:

A

disease states– affects the volume of distribution and clearance

acute viral hepatitis alters the plasma and tissue it DOES NOT change volume but increases clearance because more free drug (not bound to protein).

63
Q

accumulation factor

A

accumulation factor = 1/ fraction lose in one dosing interval

When drug doses are REPEATED the drug accumulates in body until dosing stops

if the dosing interval is SHORTER than 4 half-lives (a week) then the accumulations will be detectable

64
Q

loading dose

A

is used to produce a therapeutically effective blood level without delay

loading dose makes a larger initial dose

65
Q
A
66
Q
A

Pharmcology (2 decks)

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