Pharmacokinetics Flashcards

1
Q

Absorption

A

Process by which drug enters a system in circulation followed by illustration of mouth inhalation, through skin or injection

Passage of drug from site of administration into plasma

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2
Q

What are the 4 main mechanisms for movement of small molecules?

A

Passive diffusion through lipid- conc gradient, best small and hydrophobic
Facilitated passive diffusion- molecules more polar, charged, carried molecule, with conc gradient
Active transport
Pinocytosis

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3
Q

Acidic drug best absorbed at which levels?

A

Acidic environments

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4
Q

What is sublingual administration?

A

Placing drug under tongue, to dissolve, absorb into blood stream through tissue there

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5
Q

What is transdermal administation?

A

Through skin to bloodstream

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6
Q

What are the factors affecting absorption from GI tract?

A

Particle size and formulation- liquid dissolve more quickly
Physiochemical factors- molecular sizing
Gut content- faster absorption on empty
GI motility- gastric emptying determines how quickly drug delivered to small intestine
Splanchnic blood flow- reduced in heart failure, give reduced absorption

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7
Q

What is IV administration?

A

Direct administration into plasma

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8
Q

Bioavailability

A

The fraction of the administered dose that reached the systemic circulation as the parent drug

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9
Q

Reason for incomplete bioavailability for oral admin

A

Incomplete absorption and loss in faeces

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10
Q

How does bioavailability of a drug affect the dose

A

Poor bioavailability will need a higher dose

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11
Q

Distribution

A

Process by which drug is transferred reversibly between the plasma and the tissues

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12
Q

Distribution is dependent on which 2 factors

A

Blood flow

Lipid solubility - lipid soluble more likely to cross blood brain barrier causing less side effects

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13
Q

Why are lipid soluble drugs more likely to be more slowly released from body

A

Tissue store of lipid soluble drug will be higheer resulting in slower elimination

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14
Q

Oral distribution of drug

A

Gradual increase in blood

Even filling of all compartments

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15
Q

IV distribution of drug

A

Rapid rise of drug in blood
Rapid rise in vessel rich
Slow rise in intermediate and poor vessel
Drug redistributed from vessel rich so become equal

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16
Q

Volume of distribution

A

Theoretical volume necessary to contain total amount of an administered drug at same conc that is observed in blood plasma

17
Q

Volume of distribution equation

A

total amount of drug in body/ plasma conc

18
Q

Low volume distribution drugs

A

Large, water soluble

Stay within plasma

19
Q

High volume distribution drugs

A

Small lipid soluble

Distribute into all compartments

20
Q

What is principle site of drug metabolism?

21
Q

What does liver do?

A

Aim to make drug more soluble for elimination via kidneys

22
Q

Metabolism of drug affected by 3 factors

A

Enzyme induction or inhibition
Blood flow to liver
Genetic variation in enzymes

23
Q

How do enzyme inhibitors affect activity of drug?

A

Increase activity

24
Q

How do enzyme inducers affect activity of drug?

A

Reduce activity

25
Pro-drug
Drug that is metabolised after administration to a pharmacologically active metabolite adminstered inactive form, reduces undersirable effects
26
Larger molecules are excreted how?
By bile (removed in faeces)
27
Smaller moelcules are excreted how?
Renally (urine)
28
What is first order drug elimination
Metabolism rate is proportional to drug plasma conc | Drug conc drops by fixed percentage in given time
29
What is zero order drug elimination?
Metabolism removes fixed amount of drug in given period
30
Half life of drug
Time it takes for plasma conc or amount of drug in body to be reduced by 50%
31
Clearance equation
Rate of elimination from body/ drug conc in plasma
32
Cl total equation
Cl renal + clearance non renal
33
Repeated administration
Drug administration of fixed dose at regular time interval through given route
34
Drug drug interactions
When one drug affects the activity of another when 2 are given in combination
35
Therapeutic index equation
Dose resulting in toxicity/ dose giving therapeutic response
36
High TI indicates what toxicity
Low risk of toxicity
37
Low TI or narrow indicated what
High risk of toxicity