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Pharmacology > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

what is drug bioavailability

A

the fraction of unchanged drug reaching the systemic circulation following administration by any route

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2
Q

what factors affect bioavailability for drugs taken orally?

A
  • extent of absorption (lack of absorption from gut - too hydrophobic/lipophobic), reverse transported associated with P-glycoprotein
  • first pass elimination (amt excreted by liver)
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3
Q

why do people with poor liver function require a smaller dose of a drug?

A

because less is eliminated by a liver with less function, so more drug remains in the bloodstream.

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4
Q

what is distribution?

A

the process of reversible transfer of a drug between one site and another within the body (one of which is usually blood) eg from b/s to tissue, or from b/s to lrgan).

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5
Q

What are the factors affecting distribution?

A 
plasma protein binding
tissue binding
blood brain barrier
placental barrier
blood supply
capillary permeability
cardiovascular function
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6
Q

How does protein binding decrease the concentration of free drug available for distribution to the site of action?

A

Drug binds with proteins to form drug-protein complex. The Decreases the amount of drug available for distribution. Is a reversible and dynamic process with bound and unbound drug in eqm. When free drug is eliminated drug-protein complex dissociates to maintain eqm. Only free or unbound drug is able to exert a pharmacological effect.

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7
Q

what factor determines the extent of protein binding that occurs?

A

The affinity of the drug for the protein

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8
Q

What type of protein do acidic drugs mainly bind to?

A

albumin

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9
Q

What type of protein do basic drugs mainly bind to?

A

glyco-protein

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10
Q

What can happen to protein binding if two drugs are given at the same time?

A

They can compete with each other for the same binding sites and displace each other. The drug with less affinity for binding site will be more bioavailable, and have more effect on body (eg side effects) as less of it will be bound.

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11
Q

What effect does a decrease in blood proteins have on distribution?

A

There is less protein to bind to, so an increase in free drug concentration and effects.

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12
Q

what causes a decrease in blood proteins?

A
  • dietary protein insufficiency
  • liver disease (leads to decreased synthesis of plasma proteins)
  • burns (lose a lot of protein, bloodstream becomes deficient
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13
Q

What effect does an increase in blood proteins have on distribution?

A

Causes a decrease in free drug concentration and effects.

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14
Q

what is pharmacokinetics

A

What the body does to the drug

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15
Q

what is pharmacodynamics

A

what the drug does to the body

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16
Q

definition of metabolism (biotransformation)

A

chemical modification of a drug by enzymes (usually into less active products)

17
Q

What are the two reactions that occur in drug metabolism?

A

functionalisation and conjugation

18
Q

What did the two reactions in drug metabolism used to be known as?

A

Phase 1 and phase 2.

19
Q

What type of reactions occur in functionalisation reactions?

A

oxidation, reduction, hydrolysis

20
Q

What type of reaction occurs in conjugation reactions?

A

joining of a drug or its polar metabolite with an endogenous substance (eg glucuronic acid, sulfate, acetyl CoA, or glutathione)

21
Q

what is the purpose of conjugation reactions?

A

to make a substance more polar or water-soluble to enhance urinary excretion.

22
Q

what is ‘first pass metabolism’?

A

The amount of drug left to enter systemic circulation after undergoing liver biotransformation

23
Q

Which enzymes mainly carry out functionalisation reactions?

A

cytochrome P450 (CYP) enzymes

24
Q

What 4 factors influence metabolism?

A

genetic factos
age
disease states
environmental factors (eg drug interactions0

25
Q

what is induction of metabolism

A

increased enzyme activity leading to faster metabolism of other substances metabolised via the same enzymes

26
Q

what is an example of induction of metabolism?

A

cigarette smoke increases activity of one of the CYP enzyme pathways, which increases the rate of metabolism of caffeine and other drugs.

27
Q

What is inhibition of metabolism

A

pharmacokinetic competition between two drugs for the same metabolic enzyme pathways.

28
Q

what is first pass metabolism

A

how much drug is left to enter systemic circulation after it has undergone liver biotransformation

29
Q

what are the main routes of excretion?

A

hepatic (billary), kidneys, expired air, sweat and saliva, breast milk

30
Q

through which two routes are drugs excreted via the kidneys?

A

glomerular filtration and active tubular excretion

31
Q

What is clearance?

A

the ability of an individual organ or the whole body to eliminate a drug

Pharmacology (7 decks)

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