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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
What do phase 1 enzymes like CYP450 do?
Inactivate drug
26
What do phase 2 enzymes do?
Make drugs soluble by conjugating- this means we can eliminate them
27
What is Bioavailabilty? Consider what it would be for IV drugs.
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
Oral bioavailabilty is often compared with which other administration route?
IV | Oral/IV
29
List the three phases of drug distribution.
1. Bulk Flow- vasculature is a long way 2. Diffusion - moving between body compartments 3. Barriers to diffusion - interactions, permeability, non target binding
30
Which organs contain sinusoids?
Liver and spleen
31
Where do you find continuous endothelial cells?
Blood brain barrier
32
List factors that affect drug distribution.
``` Lipophilicity Capillary permeability Drug pKa, Local pH OAT, OCT presence Degree of drug binding to proteins ```
33
What affect does drug protein binding have?
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
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?
42L 14L 3L
35
What is the apparent volume distribution?
Groups all the main fluid compartments together and references it to plasma conc- all depends on push factors. Vd= drug dose/ [plasma drug]
36
What does a small volume distribution mean?
Less penetration of the interstitial fluid
37
Elimination covers both .... and .... processes
metabolic and excretory
38
Metabolism of drugs in the liver and other tissues to a lesser extent is split into?
Phase I and Phase II
39
Why is the liver the first port of call for drug metabolism?
Hepatic portal system is the first place the venous drainage from the gut goes.
40
Why do we want to make drugs lipophilic in the liver?
Enhance renal elimination.
41
Phase I metabolism involves what reactions that increase the ionic charge of a molecule?
Hydorxylation dealkylation REDOX
42
What happens to a pro-drug when it meets greatest CYP450 in phase I metabolism?
Its activated metabolite is formed
43
What type of drug is codeine?
Pro drug converted to mophine
44
Where in a cell are phase II enzymes mainly found?
Cytosol
45
What reactions do phase II enzymes do to further increase ionic charge on the drugs?
``` Sulphanation Glucorinadation Glutathione conjugation Methylation N-acteylation ```
46
How can we eliminate drugs?
Kidney in urine | gall bladder as bile
47
Name the 3 CYP450 super families
CYP 1,2,3
48
Why is CYP450 so important in pharmacology?
6 isoenzymes that metabolise 90% of prescription meds
49
What patient specific factors affect drug metabolism?
Age Sex General health status
50
If two drugs are given simultaneously can they effect each others metabolism?
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
How does grape fruit juice effect verapamil?
Inhibits CYP3A4
52
30% of asians do not express CYP2C19 which is involved in metabolising what specific drugs?
Omeprazole Valium Phenytoin
53
What happens to people who rapidly metabolism pro-drugs?
they may get toxic effects at a lower dose
54
urine, breast milk, sweat, tears, genital secretions, saliva, breath and bile are all routes of?
Drug elimination
55
What are the three processes of renal excretion for drugs?
Glomerular filtration Active tubular secretion Passive tubular secretion
56
What is drug clearance?
Rate of elimination - volume of plasma completely cleared of the drug per unit time.
57
Designing dosing schedules, therapeutic regimens and minimising ADRs (adverse drug rxs) we must consider... and ...
Vd | clearance
58
Whats a drug half life?
The amount of time over which the plasma conc of a drug halves. (log of plot is linear)
59
The rate of metabolism and excretion is proportional to the conc of the drug if....
plenty of phase 1 and 2 enzymes | Plenty of SLCs
60
What is zero order drug elimination?
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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