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Year 1 Intro to Pharmacology and Physiology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Name the 4 main processes in pharmacokinetics:

A

Absorption
Distribution
Metabolism
Elimination

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2
Q

What’s the most common method of drug administration?

A

Oral

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3
Q

List the 6 methods of drug administration:

A

Enteral routes: Oral, sublingual and rectal.

Parenteral: Intravenous, subcutaneous and intramuscular.

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4
Q

What distinguishes enteral and parenteral?

A

Enteral is delivered to the internal body environment by the GI tract.
Parenteral delivery does not involve the GI tract.

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5
Q

What helps oral drug absorption?

A

Gut motility mixing and presenting drugs to intestinal epithelia.
Large surface area on small intestine.

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6
Q

What are the routes of drug administration?

A

Oral
Intravenous transdermal
Intramuscular subdermal
Sublingual Inhaltion Rectal

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7
Q

What is the normal transit time of the small intestine?

A

3-5hrs

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8
Q

Name a large molecule in antibiotics that are transported across the gut epithelium using H+ ions?

A

B-lactam

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9
Q

Which common antidepressant is cotransported with Na+ in the gut?

A

Fluoxetine/ Prozac

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10
Q

What is the pH of the gut?

A

6

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11
Q

How does the gut pH help facilitated diffusion of weak acids and bases?

A

The drug will protonate or deprotonate depending on its pKa then organic anion/ cation transporters will allow them to permeate the membrane.

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12
Q

Name a common lipophillic drug

A

Steroids

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13
Q

Does secondary active transport use ATP?

A

No

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14
Q

List physiochemical actors affecting drug absorption:

A

GI length and surface area
Drug lipophilicity/ pKa
Distribution of secondary active transporters/ solute carrier transporters

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15
Q

How does eating a meal affect gut motility and drug absorption?

A

Blood flow to the gut is increased after a meal.
Motility is slowed after a meal
Food can increase or reduce absorption. Low pH in the gut may destroy drugs.

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16
Q

Why are mathematical models of pharmacokinetics useful even though they aren’t an exact replica of the real body systems?

A

Describes and predicts changing drug concentrations over time through out the body. This gives us an idea of how to optimise therapeutic effect.

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17
Q

The mneumoin Oi It Is Sir helps remember routes of administration, please list the routes.

A

Oral
IV

Intra-muscular
Transdermal

Inhalation
Sublingual

Subcutaneous
Intra-nasal
Rectal

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18
Q

List the 4 methods of drug absorption

A

Passive diffusion
Facilitated diffusion
Primary or secondary active transport
Pinocytosis

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19
Q

What type of drugs can be passively diffused?

A

Lipophilic like steroids

Weak acids and bases because they portent or deprotonate

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20
Q

What is the name given to the molecules that help drugs be absorbed by facilitated diffusion and or secondary active transport?

A

Solute carrier transport

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21
Q

What drives solute carrier transport?

A

the electrochemical gradient of the clout molecule

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22
Q

Name the two types of solute carrier transporter.

A

OAT- organic anion transporter

OCT- organic cation transport

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23
Q

Solute carrier transport is important in two parts of pharmacokinetics, what are they?

A

Absorption and elimination

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24
Q

What is first pass metabolism?

A

Reducing the availability of the drug before it reaches systemic circulation, this can happen in the liver or in the Gi tract itself.

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25
Q

What do phase 1 enzymes like CYP450 do?

A

Inactivate drug

26
Q

What do phase 2 enzymes do?

A

Make drugs soluble by conjugating- this means we can eliminate them

27
Q

What is Bioavailabilty? Consider what it would be for IV drugs.

A

Fraction of a defined dose that reaches a specific body compartment (generally the circulation is the compartment referenced).
For IV administration the bioavailability reference would be 100%.

28
Q

Oral bioavailabilty is often compared with which other administration route?

A

IV

Oral/IV

29
Q

List the three phases of drug distribution.

A
  1. Bulk Flow- vasculature is a long way
  2. Diffusion - moving between body compartments
  3. Barriers to diffusion - interactions, permeability, non target binding
30
Q

Which organs contain sinusoids?

A

Liver and spleen

31
Q

Where do you find continuous endothelial cells?

A

Blood brain barrier

32
Q

List factors that affect drug distribution.

A 
Lipophilicity 
Capillary permeability 
Drug pKa, Local pH
OAT, OCT presence
Degree of drug binding to proteins
33
Q

What affect does drug protein binding have?

A

Free drugs bind proteins and are then inactive and the free drug levels are reduced. This protein bound drug is a reservoir of drug that is an equilibrium with the free from.

34
Q

How much fluid is in the average 70kg man and how much of that is extracellular and of the extracellular fluid how much is our plasma?

A

42L
14L
3L

35
Q

What is the apparent volume distribution?

A

Groups all the main fluid compartments together and references it to plasma conc- all depends on push factors.
Vd= drug dose/ [plasma drug]

36
Q

What does a small volume distribution mean?

A

Less penetration of the interstitial fluid

37
Q

Elimination covers both …. and …. processes

A

metabolic and excretory

38
Q

Metabolism of drugs in the liver and other tissues to a lesser extent is split into?

A

Phase I and Phase II

39
Q

Why is the liver the first port of call for drug metabolism?

A

Hepatic portal system is the first place the venous drainage from the gut goes.

40
Q

Why do we want to make drugs lipophilic in the liver?

A

Enhance renal elimination.

41
Q

Phase I metabolism involves what reactions that increase the ionic charge of a molecule?

A

Hydorxylation
dealkylation
REDOX

42
Q

What happens to a pro-drug when it meets greatest CYP450 in phase I metabolism?

A

Its activated metabolite is formed

43
Q

What type of drug is codeine?

A

Pro drug converted to mophine

44
Q

Where in a cell are phase II enzymes mainly found?

A

Cytosol

45
Q

What reactions do phase II enzymes do to further increase ionic charge on the drugs?

A 
Sulphanation 
Glucorinadation 
Glutathione conjugation 
Methylation 
N-acteylation
46
Q

How can we eliminate drugs?

A

Kidney in urine

gall bladder as bile

47
Q

Name the 3 CYP450 super families

A

CYP 1,2,3

48
Q

Why is CYP450 so important in pharmacology?

A

6 isoenzymes that metabolise 90% of prescription meds

49
Q

What patient specific factors affect drug metabolism?

A

Age
Sex
General health status

50
Q

If two drugs are given simultaneously can they effect each others metabolism?

A

yes, by inducing or inhibiting CYP450

Note if one drug induced CYP450 isoenzymes then a drug given at the same time will have a lower than expected plasma concentration because it will under go higher rates of first pass metabolism

51
Q

How does grape fruit juice effect verapamil?

A

Inhibits CYP3A4

52
Q

30% of asians do not express CYP2C19 which is involved in metabolising what specific drugs?

A

Omeprazole
Valium
Phenytoin

53
Q

What happens to people who rapidly metabolism pro-drugs?

A

they may get toxic effects at a lower dose

54
Q

urine, breast milk, sweat, tears, genital secretions, saliva, breath and bile are all routes of?

A

Drug elimination

55
Q

What are the three processes of renal excretion for drugs?

A

Glomerular filtration
Active tubular secretion
Passive tubular secretion

56
Q

What is drug clearance?

A

Rate of elimination - volume of plasma completely cleared of the drug per unit time.

57
Q

Designing dosing schedules, therapeutic regimens and minimising ADRs (adverse drug rxs) we must consider… and …

A

Vd

clearance

58
Q

Whats a drug half life?

A

The amount of time over which the plasma conc of a drug halves. (log of plot is linear)

59
Q

The rate of metabolism and excretion is proportional to the conc of the drug if….

A

plenty of phase 1 and 2 enzymes

Plenty of SLCs

60
Q

What is zero order drug elimination?

A

As the drug conc increases the rate of elimination plateaus ( you are working at max to metabolise and eliminate) More likely to get toxicity and ADR.

Year 1 Intro to Pharmacology and Physiology (8 decks)

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