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Pharmocokinetics > Administering drugs topically > Flashcards

Administering drugs topically Flashcards

1
Q

why not all drugs administered orally?

A

site of action best treated topically e.g skin disease
due to their pharmacological, biological and chemical properties
risk of significant systemic side effects

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2
Q

example of why insulin not administered orally? and why?

A

insulin because its a peptide and if taken orally would be destroyed by gut digestive enzymes

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3
Q

administered topical drugs can have what 2 effects?

A

systemic or local

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4
Q

example of route administration that has a systemic effect topically

A

patch, inhalation

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5
Q

example of route administration that has a local effect topically

A

creams, ocular drops

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6
Q

define local effect

A

drug applied to a localized area of body surface to minimize systemic side effects

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7
Q

define systemic effect

A

drug applied to a body surface to provide an alternative and convenient route into blood

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8
Q

why spray (eg. GTN for narrowing artery / drug) under the tongue?

A

tongue set up to absorb things, loads of blood supply

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9
Q

Some examples when topical route of administration is used locally?

A

to the skin (eczema), eye (conjunctivitis), nose (hay fever) ,lung (asthma) , rectum (constipation) , vagina (thrush)

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10
Q

Some examples when topical route of administration is used systemically?

A

to the skin (contraception), mouth mucosal membranes (chest pain)

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11
Q

steroid is a drug that can be formulated in many different ways to target different tissues examples:

A

eczema is cream, asthma is inhaled powder, nose is nasal spray

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12
Q

stratum corneum

A

outer layer of epidermis , multiple layered and lipid rich

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13
Q

passage of drug through stratum corneum is dependent on?

A

whether it is lipophilic (utilises intracellular route- readily across cell walls)
or hydrophilic (utilises the intercellular route- diffusing in fluid filled spaces between cells)

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14
Q

paracellular transport

A

transfer of substances across an epithelium by passing through the intercellular space between the cells

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15
Q

transcellular transport

A

substance travels through the cell, passing through membrane

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16
Q

lipophilic drug will use what type of transport

A

transcellular

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17
Q

hydrophilic drug will use what type of transport

A

paracellular

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18
Q

ointments can be

A

non-emulsifying (lipophilic) or water soluble (lipophilic and hydrophilic)

19
Q

non- emulsifying ointments contain

A

beeswax and paraffin

20
Q

disadvantage of water soluble ointment

A

easily washed off

21
Q

disadvantage of non-emulsifying ointments

A

messy and inconvenient

22
Q

creams can be either

A

lipophilic (water in oil) or hydrophilic (oil in water)

23
Q

beeswax in drug formulation

A

drug product stays on skin (harder to wash off)
hole of skin moist so more likely to absorb the drug

24
Q

physiological response for when bronchioles not receiving not enough oxygen

A

diverts blood to parts of the lung that have no air getting to it to the bits of the lug that have air getting to it

25
Q

key points for drug formulations

A

target site appropriate
drug properties (is drug stable in particular formulation?)
Acceptability to patient

26
Q

transdermal application

A

delivery system that releases drug through a rate controlling membrane into the skin

27
Q

transdermal application works how?

A

reservoir of drug time (lipophilic mostly) allows released delivery of reservoir

28
Q

Topical drug administration

A

Applying medication directly to a particular place on or in the body

29
Q

Steroids given orally can cause?

A

Immune suppression, high blood pressure and diabetes

30
Q

73 year old with severe chest at the gp practice. He needs GTN treatment. This can be given as a GTN spray or IV. There is no oral route. Why? What route can be used?

A

No oral route = subject to extensive first pass metabolism in the liver
Substantially higher doses required= side effects
IV (in hospital) or topically ( spray)
- well absorbed across mucosal surface of mouth

31
Q

Drugs are given locally because we can easily access that area of the body. What does this mean?

A

Means the drug targets the tissue, without affecting other receptors in the rest of the body-minimising side effects

32
Q

Drug applied to the skin may diffuse from the stratum corneum to?

A

Dermis- capillary microcirculation- systemic circulation

33
Q

How can you increase water content of the stratum corneum? What is the effect of this?

A

Occlusion (blockage/closing of blood vessel or hollow organ) or hydration
Means increased penetration of both lipophilic and hydrophilic drugs

34
Q

Routes to treat lung topically

A

Powder
Aerosol
Nebulised solution
Salbutamol (beta 2 agonist)

35
Q

Why might inhaling drug be good topically?

A

Large surface area-rapid local absorption
Ensure high Local concentration
Local side effects

36
Q

Formulations to consider for topical drugs

A

Target site
Drug properties-is the active ingredient stable in a particular formulation?
Acceptability to patient

37
Q

Topical application-systemic effect:
Does this route avoid first pass metabolism?

A

Yes

38
Q

Example of topical application with systemic effect

A

Inhaled anaesthetics
Buccal midazolam
Sublingual GTN tablet
Transdermal nicotine patch

39
Q

Advantage of transdermal application

A

Avoids fluctuation in plasma concentration
Easy to administer and acceptable to patients
Can be stopped easily
Prolonged drug action

40
Q

Disadvantage of transdermal application

A

Only small enough molecules can penetrate the skin this way
Not applying the patch appropriately will affect the dose
Local side effects
Slow to initiate effect

41
Q

Advantage of topical drug administration

A

Alternative route if oral not possible
Targets intended site of action
Reduced risk of systemic side effects
High drug concentration can be achieved
Generally accepted by patients

42
Q

Disadvantage of topical drug administration

A

Variable time of onset
Still some systemic absorption of drugs
Local side effect e.g. stinging, may be messy/inconvenient
Rapid clearance may require regular administration

43
Q

Increasing the water content of the stratum corneum via occlusion (blockage/closing of blood vessel or hollow organ) or hydration will result in?

A

increased penetration of both lipophilic & hydrophilic drugs

44
Q

salbutamol acts on what receptor? has what effect?

A

B2 adrenoceptor agonist
acts on smooth muscle and dilates bronchi

Pharmocokinetics (22 decks)

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