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Pharmacology > 01&02 - Drug Absorption&Administration > Flashcards

01&02 - Drug Absorption&Administration Flashcards

1
Q

what is pharmacology

A

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

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2
Q

what s medical pharmacology

A

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

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3
Q

types of medical pharmacology

A

PHARMACOGENOMICS
PHARMACOEPIDEMIOLOGY
PHARMACOECONOMICS
TOXICOLOGY

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4
Q

what is pharmacokinetics

A
  • 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
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5
Q

pharmacodynamics

A
  • 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
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6
Q

describe the pathways of a drug

A

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

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7
Q

what happens during distribution of the drug

A

drug in extracellular fluid & intracellular sites

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8
Q

what happens during elimination of the drug

A

drug metabolized or exerted

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9
Q

what 3 factors affect the pharmacological effect

A
  1. regimen specific
  2. drug specific
  3. patient specific
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10
Q

regimen specific

A

dose
frequency
route

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11
Q

drug specific

A 
Dose-response relationship
Site of Biological Effect
Disposition of the Drug
Potency of the Drug
Dosage Form
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12
Q

patient specific

A 
Environmental/Dietary Exposures
Psychological Condition
Genetic Constitution
Organ Function
Enzyme Activity
Age/Sex
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13
Q

different plasma concentration of phenytoin can cause what

A

mental changes
ataxia
nystagmus

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14
Q

routes of drug administration

A

topical
enteral
parenteral
specific sites/cavities

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15
Q

topical

A

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

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16
Q

enteral

A

oral route, putting directly into GI

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17
Q

parenteral

A
  • by injection (ie. subcutaneous, intramuscular and IV), patches
  • bypass GI?
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18
Q

specific sites/cavities

A

intra-articular (ie. into joint, bladder irrigation)

-implants that rleease AB at a certain time

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19
Q

intravenous route absorption

A

100%; potentially immediate onset

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20
Q

intravenous route special utility

A

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

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21
Q

intravenous route limitations

A

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

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22
Q

subcutaneous absorptions

A

may be prompt or sustained

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23
Q

subcutaneous special utility

A

may be used for suspensions or slow-release implants

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24
Q

subcutaneous limitations

A

not suitable for large volumes or irritating substances

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25
Q

oral ingestion absorption

A

variable, depends on many factors

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26
Q

oral ingestion special utility

A

convenient; economical; generally safe

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27
Q

oral ingestion limitations

A

dependent on patient compliance, bioavailability potentially erratic

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28
Q

mechanisms of drug transport

A 
Passive diffusion
Facilitated/Active transport
Filtration
Endocytosis
Ion-pair transport
29
Q

name a few drug transporters

A
  1. membrane proteins

2. superfamilies - ABC and SLC

30
Q

what are membrane proteins

A

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

31
Q

what are the 2 major superfamilies of drug transporters

A
  1. ABC

2. SLC

32
Q

what is ABC

A

ATP binding cassette

33
Q

what is SLC

A
  • solute carrier

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

34
Q

what are drug transporters

A
  • 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
Q

some drug transporters serve as

A
  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
Q

pharmaceutical factors of GI absorption and passive diffusion

A

dosage form must first dissolve into solution

37
Q

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

A

molecular size
lipid solubility
ionization coefficient (pKa)

38
Q

Fick’s Law of Diffusion

A

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

39
Q

Gastrointestinal Factors

A

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

40
Q

Ionization and Effect of pH

A
  • 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
Q

the degree of ionization depends on what

A

the pKa of the drug and the local pH

42
Q

Henderson-Hasselback Equation

A

pH – pKa = log (base)/(acid)

43
Q

weak acid H-H equation

A

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

44
Q

weak base H-H equation

A

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

45
Q

lipid solubility

A

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

46
Q

importance of absorptive surface area

A

drug absorption is fastest from the small intestine

47
Q

absorption is facilitated at sites where

A

ionization is suppressed/unionized

48
Q

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

A

the overall rate of drug absorption

49
Q

the absorption of weak bases is particularly dependent on

A

arrival in the small intestine

50
Q

drugs tend to accumulate in

A

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

51
Q

what factors play a role in oral drug absorption

A
  • drug instability
  • food
  • gastric emptying
  • intestinal transit
  • transporters
  • villous blood flow
  • drug-drug interactions
52
Q

transporters can be a source of what

A

drug interactions affecting the rate of drug absorption and distribution

53
Q

what 3 fluid compartments do drugs distribute into

A
  1. vascular
  2. interstitial
  3. intracellular
54
Q

volume of distribution (Vd) relates to what

A

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

55
Q

equation for Vd

A

dose/ [plasma]

56
Q

Vd values exceeding total body water indicated what

A

binding or sequestration at an extravascular site

57
Q

along with clearance (Cl), Vd determines what

A

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

58
Q

changes in Vd can be explained by what

A

drug interactions and differences in drug response

59
Q

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

A

usually reversible

60
Q

drugs binding to plasma proteins are governed by what law

A

law of mass action

61
Q

what are the main protein targets drugs bind to

A
  1. albumin
  2. α1-acid glycoprotein
  3. lipoproteins
62
Q

what does albumin bind to

A

binds mostly to weak acids

63
Q

what does α1-acid glycoprotein bind to

A

mostly organic bases

64
Q

what do lipoproteins bind to

A

lipid soluble drugs

65
Q

what are consequences of plasma protein binding

A
  • 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
Q

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

A
  • high degree of protein binding
  • low Vd for displaced drug
  • slow elimination kinetics of displaced drug
67
Q

absorption of intramuscular

A

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

68
Q

special utility of intramuscular

A

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

69
Q

limitations of intramuscular use

A

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

Pharmacology (23 decks)

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