01&02 - Drug Absorption&Administration Flashcards Preview

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Flashcards in 01&02 - Drug Absorption&Administration Deck (69):
1

what is pharmacology

the study of substances that interact with living systems through chemical processes

2

what s medical pharmacology

the science of substances used to prevent, diagnose and treat disease

3

types of medical pharmacology

PHARMACOGENOMICS
PHARMACOEPIDEMIOLOGY
PHARMACOECONOMICS
TOXICOLOGY

4

what is pharmacokinetics

-relationship between drug dosage and time-course of drug concentration in the body, usually as reflected in plasma drug concentrations
-what the body does to the drug

5

pharmacodynamics

-concerned with the mechanism of drug action, including the relationship btwn drug concentration and the magnitude of effect (dose-response)
- what the drug goes to the body

6

describe the pathways of a drug

dose of drug administered--> (absorption)-->drug concentration in systemic circulation --> (distributed OR Elimination) --> drug concentration at site of action --> pharmacological effect --> clinical response --> toxicity OR Efficacy

7

what happens during distribution of the drug

drug in extracellular fluid & intracellular sites

8

what happens during elimination of the drug

drug metabolized or exerted

9

what 3 factors affect the pharmacological effect

1. regimen specific
2. drug specific
3. patient specific

10

regimen specific

dose
frequency
route

11

drug specific

Dose-response relationship
Site of Biological Effect
Disposition of the Drug
Potency of the Drug
Dosage Form

12

patient specific

Environmental/Dietary Exposures
Psychological Condition
Genetic Constitution
Organ Function
Enzyme Activity
Age/Sex

13

different plasma concentration of phenytoin can cause what

mental changes
ataxia
nystagmus

14

routes of drug administration

topical
enteral
parenteral
specific sites/cavities

15

topical

skin, mucous membranes, oral pharynx, eye, inside of ear, pulmonary

16

enteral

oral route, putting directly into GI

17

parenteral

-by injection (ie. subcutaneous, intramuscular and IV), patches
-bypass GI?

18

specific sites/cavities

intra-articular (ie. into joint, bladder irrigation)
-implants that rleease AB at a certain time

19

intravenous route absorption

100%; potentially immediate onset

20

intravenous route special utility

emergency use: permits dosage titration; may be the only suitable route; suitable for larger volumes & irritating substances when diluted

21

intravenous route limitations

increase risk of ADRs; not suitable for oily or insoluble substances

22

subcutaneous absorptions

may be prompt or sustained

23

subcutaneous special utility

may be used for suspensions or slow-release implants

24

subcutaneous limitations

not suitable for large volumes or irritating substances

25

oral ingestion absorption

variable, depends on many factors

26

oral ingestion special utility

convenient; economical; generally safe

27

oral ingestion limitations

dependent on patient compliance, bioavailability potentially erratic

28

mechanisms of drug transport

Passive diffusion
Facilitated/Active transport
Filtration
Endocytosis
Ion-pair transport

29

name a few drug transporters

1. membrane proteins
2. superfamilies - ABC and SLC

30

what are membrane proteins

that control the influx of essential nutrients, ions (and certain drugs) and the efflux of toxins and certain drugs

31

what are the 2 major superfamilies of drug transporters

1. ABC
2. SLC

32

what is ABC

ATP binding cassette

33

what is SLC

-solute carrier
-transport polypeptides (OATP), organic anions (OAT), and cations (OCT)

34

what are drug transporters

-play protective roles
-reducing drug absorption from the GI tract
-enhancing drug elimination into bile and urine
-impeding access of drugs to the brain and placenta

35

some drug transporters serve as

1. drug targets (eg. neurotransmitters uptake; cholesterol uptake; Na+-H+ exchange) and can be a source of drug interactions
2. drug resistance (antivirals; anticancer agents)

36

pharmaceutical factors of GI absorption and passive diffusion

dosage form must first dissolve into solution

37

chemical properties of the drug that affect GI absorption and passive diffusion

molecular size
lipid solubility
ionization coefficient (pKa)

38

Fick's Law of Diffusion

Flux = (C1-C2) x [(Area x perm Coefficient)/Membrane Thickness]

39

Gastrointestinal Factors

Gastric emptying time; intestinal transit
Presence of food
Local blood flow
Local pH

40

Ionization and Effect of pH

-most drugs are weak electrolytes
-the mucosal lining of the GI tract is largely impermeable* to the ionized form of a weak acid or base

*ionized forms may be candidates for some transporters

41

the degree of ionization depends on what

the pKa of the drug and the local pH

42

Henderson-Hasselback Equation

pH – pKa = log (base) /(acid)

43

weak acid H-H equation

pH-pKa= log [RCOO-] / [RCOOH}

44

weak base H-H equation

pH-pKa = log [RNH2] / [RNH3+]

45

lipid solubility

for a given pKa (and therefore relative degree of ionization) the larger the lipid solubility, the more rapid is absorption

46

importance of absorptive surface area

drug absorption is fastest from the small intestine

47

absorption is facilitated at sites where

ionization is suppressed/unionized

48

the rate at which the stomach empties has a significant effect on

the overall rate of drug absorption

49

the absorption of weak bases is particularly dependent on

arrival in the small intestine

50

drugs tend to accumulate in

fluid/tissue compartments where the degree of ionization is the greatest (ion trapping)

51

what factors play a role in oral drug absorption

-drug instability
-food
-gastric emptying
-intestinal transit
-transporters
-villous blood flow
-drug-drug interactions

52

transporters can be a source of what

drug interactions affecting the rate of drug absorption and distribution

53

what 3 fluid compartments do drugs distribute into

1. vascular
2. interstitial
3. intracellular

54

volume of distribution (Vd) relates to what

relates the amount of drug in the body to the plasma concentration (simple dilution principle)

55

equation for Vd

dose/ [plasma]

56

Vd values exceeding total body water indicated what

binding or sequestration at an extravascular site

57

along with clearance (Cl), Vd determines what

the pharmacokinetic behaviour of a drug (Ke= Cl/Vd)

58

changes in Vd can be explained by what

drug interactions and differences in drug response

59

drugs binding to plasma proteins, are they reversible or irreversible?

usually reversible

60

drugs binding to plasma proteins are governed by what law

law of mass action

61

what are the main protein targets drugs bind to

1. albumin
2.α1-acid glycoprotein
3. lipoproteins

62

what does albumin bind to

binds mostly to weak acids

63

what does α1-acid glycoprotein bind to

mostly organic bases

64

what do lipoproteins bind to

lipid soluble drugs

65

what are consequences of plasma protein binding

-reduces the concentration of unbound free (drug)
-may slow the distribution and/or elimination of the drug (functioning as a depot)
-represents a potential site of drug interaction

66

the risk of an adverse effect from drug interaction/displacement based on protein binding is increased with the presence of?

-high degree of protein binding
-low Vd for displaced drug
-slow elimination kinetics of displaced drug

67

absorption of intramuscular

similar absorption characteristics as subcuatenous (may be prompt or sustained)

68

special utility of intramuscular

can accept large volumes than subcuatneous as well as some irritating substances

69

limitations of intramuscular use

not for use on patients on anticoagulants; may release muscle enzymes temporarily interfering with some diagnostic tests