Administering drugs topically

Question 1

why not all drugs administered orally?

Answer 1

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

Question 2

example of why insulin not administered orally? and why?

Answer 2

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

Question 3

administered topical drugs can have what 2 effects?

Answer 3

systemic or local

Question 4

example of route administration that has a systemic effect topically

Answer 4

patch, inhalation

Question 5

example of route administration that has a local effect topically

Answer 5

creams, ocular drops

Question 6

define local effect

Answer 6

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

Question 7

define systemic effect

Answer 7

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

Question 8

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

Answer 8

tongue set up to absorb things, loads of blood supply

Question 9

Some examples when topical route of administration is used locally?

Answer 9

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

Question 10

Some examples when topical route of administration is used systemically?

Answer 10

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

Question 11

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

Answer 11

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

Question 12

stratum corneum

Answer 12

outer layer of epidermis , multiple layered and lipid rich

Question 13

passage of drug through stratum corneum is dependent on?

Answer 13

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

Question 14

paracellular transport

Answer 14

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

Question 15

transcellular transport

Answer 15

substance travels through the cell, passing through membrane

Question 16

lipophilic drug will use what type of transport

Answer 16

transcellular

Question 17

hydrophilic drug will use what type of transport

Answer 17

paracellular

Question 18

ointments can be

Answer 18

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

Question 19

non- emulsifying ointments contain

Answer 19

beeswax and paraffin

Question 20

disadvantage of water soluble ointment

Answer 20

easily washed off

Question 21

disadvantage of non-emulsifying ointments

Answer 21

messy and inconvenient

Question 22

creams can be either

Answer 22

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

Question 23

beeswax in drug formulation

Answer 23

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

Question 24

physiological response for when bronchioles not receiving not enough oxygen

Answer 24

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

Question 25

key points for drug formulations

Answer 25

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

Question 26

transdermal application

Answer 26

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

Question 27

transdermal application works how?

Answer 27

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

Question 28

Topical drug administration

Answer 28

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

Question 29

Steroids given orally can cause?

Answer 29

Immune suppression, high blood pressure and diabetes

Question 30

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?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

Dermis- capillary microcirculation- systemic circulation

Question 33

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

Answer 33

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

Question 34

Routes to treat lung topically

Answer 34

Powder Aerosol Nebulised solution Salbutamol (beta 2 agonist)

Question 35

Why might inhaling drug be good topically?

Answer 35

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

Question 36

Formulations to consider for topical drugs

Answer 36

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

Question 37

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

Answer 37

Yes

Question 38

Example of topical application with systemic effect

Answer 38

Inhaled anaesthetics Buccal midazolam Sublingual GTN tablet Transdermal nicotine patch

Question 39

Advantage of transdermal application

Answer 39

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

Question 40

Disadvantage of transdermal application

Answer 40

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

Question 41

Advantage of topical drug administration

Answer 41

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

Question 42

Disadvantage of topical drug administration

Answer 42

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

Question 43

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

Answer 43

increased penetration of both lipophilic & hydrophilic drugs

Question 44

salbutamol acts on what receptor? has what effect?

Answer 44

B2 adrenoceptor agonist acts on smooth muscle and dilates bronchi