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CTL > pharmokinetics > Flashcards

pharmokinetics Flashcards

wk 10

1
Q

What is encompassed in pharmacokinetics?

A

How drugs are:

Absorbed in body fluids
Distributed to sites of action
Metabolised into inactive/active metabolites
Excreted by body

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2
Q

Why is the extent of absorption important?

A

Determines magnitude of response

and time of onset of action

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3
Q

What are the main routes of administration? And where are they?

A

Oral
parenteral- injection
inhalation- lungs
epithelial - via a membrane (skin, mucosa, nasal)
sublingual - under tongue
rectal

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4
Q

What are the four types of parenteral routes of administration?

A

Intravenous (via blood)
intramuscular (into the muscle)
Subcutaneous (under the skin)
intrathecal (into subarachnoid space of spine

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5
Q

What are the two ways that routs of administration can be divided?

A

Enteral
- into GI tract
-invloing/passing through intsetine

Parenteral
-not into GI tract

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6
Q

What are the chemical factors that affect the degree of GI absorption via oral route?

A

Formulation

Physical properties

Ionisation

Solubility

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7
Q

What are the physiological factors that affect oral administartion?

A

PH of GI contents

GI motility

Disorders

Presence of food

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8
Q

What are the advantages of Parenteral (intravenous) route of administration?

A

most common

-IMMEDIATE effect

-can deliver large amounts over time (infusion)

-used for drugs that can’t be orally taken or needs to be broken by first metabolism.

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9
Q

What are the disadvantages of Parenteral (intravenous) route of administration?

A

difficult to administer

-potential risk of overdose/ throbosis/ infection

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10
Q

what is an advantage and disadvantage of
Parenteral (Subcutaneous and intramuscular) administartion?

A

-A = lower rate of absorption and longer drug action

more painful and dependant on local blood flow

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11
Q

What is an example of Parenteral (Subcutaneous and intramuscular) administration?

A

insulin

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12
Q

What is inhalation only used for which can be a limiting factor of it’s use?

A

Only used for anesthetics and drugs whose site of action is the lung

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13
Q

What is an example of a drug that uses epithelial administration?

A

oestrogen patches

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14
Q

What is the advantage of Sublingual administartion?

A

Rapid absorption directly into systemic circulation without passing through liver

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15
Q

When is rectal administartion used (advantage)?

A

For drugs that have a local effect on GI tract

or

When intravenous administration is not possible

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16
Q

Why is lipid solubility the most important factor in drug absorption?

A

because drugs must be able to cross the lipid bilayer to reach their target organ.

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17
Q

What are the characterises of an ionised molecule vs unionsed molecule?

A

charged polar
water soluble

un-polar and more lipid soluble

18
Q

What determines the extent of ionisation? Explan

A

by pH of environment that drug dissolves in.

Drug will be ionised when exposed to a pH opposite to its pKa.

19
Q

When are acidic drugs more ionised?

A

in a basic environment: higher pH

20
Q

Where is most of the drug first distributed to?

A

organs with a high blood supply.

21
Q

what does the rate that a drug enters depend on?

A

permeability of capillaries for drug and perfusion

22
Q

What is Volume of Distribution?

A

Volume of fluid needed for drug to be uniformly distributed to produce observed concentration in blood

not a rel volume

23
Q

What is Volume Distribution determined by?

A

Relative strength of binding to tissue components VS compared to plasma proteins

(if tightly bound to plasma proteins stay in circulation) V= close to blood volume.

24
Q

If the drug is tightly bound to tissues…..

A

= less drug in blood = drug dissolve and large volume

25
Q

What is volume of distribution used for?

A

Indication of drug accumulation in tissue compartments

Determinants of half-life

Calculation of loading dose

26
Q

What are the two processes of drug elimination?

A

metabolism and excretion

27
Q

What is the role of lipophilic solubility in metabolism?

A

enhance passage through cell membranes and access to site of action

Hinder elimination from body

Most lipophilic compounds readily filtered into glomerulus of kidney and then reabsorbed across tubules

28
Q

What reactions occur in Phase I of metabolism? What is this and what are the subtypes?

A

Functionalisation reactions

What: functional group is added/exposed

subtypes: oxidation/ reduction/ hydrolysis etc

29
Q

What are the properties of Phase 1 of metabolism of drugs?

A

Result in loss of pharmacological activity

Form more reactive products

Important for prodrugs

30
Q

What is Phase 2 of metabolism of drugs?

A

Covalent linkage made between functional group from drug or phase 1 metabolite

31
Q

What are the properties of Phase 2 of metabolism of drugs?

A

Result in decrased activity

Produce more active metabolites

32
Q

What are the factors that affect drug metabolism?

A
  • Interactions between drugs
  • Disease status
  • eg liver and kidney disease
  • Hormonal status / gender
  • Age function declines with age
  • Nutritional status ]
  • Genetic factors
33
Q

How do inetractions between drugs affect drug metabolism?

A
  • drug induced alteration in liver enzymes
  • competition for metabolic pathways

alters rates at which drugs are metabolised

34
Q

What is oral administration limited by?

A

First-pass metabolism

Oral drugs may be inactivated in liver/intestines before enters systemic circulation = first pass metabolism

Limits oral administration because:

Higher dose needed, large and individual variation

35
Q

What is bioavalaibility?

A

Proportion of drug that passes into systemic circulation after oral administration

36
Q

What does bioavalaibility depend on?

A

Amount absorbed from GIT q Amount escaping extraction (first-pass metabolism) by the liver

37
Q

What is elimination?

A

Irreversible less of a drug via metabolism and excretion

38
Q

What is excretion?

A

irreversible loss of chemically unchanged drug in urine, bile, air or faeces

39
Q

What is clearance?

A

Availability of individual organ or body to eliminate drug

40
Q

What is Half life?

A

Time taken for amount of drug in the body (plasma concentration) to drop by half.

41
Q

What is the relationship between Half life, clearance and Vd?

A

Half-life is increased by an increase in the volume of distribution or
a decrease in clearance

42
Q
A

CTL (11 decks)

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