patches, injections and inhalers Flashcards
what is transdermal drug delivery?
drug delivered using a patch on the skin. it is a continuous drug release over a long period of time.
-the rate of delivery to be slower than the rate of absorption
does the drug enter systemic circulation in transdermal drug delivery?
yes
what are the 2 ways of controlling the rate of the release of the drug from the patches?
by matrix - drug mixed in matrix and released slowly over time,
or rate limiting membrane (drug in the reservoir)
what is the patch protected by?
an occlusive backing layer
where is the drug stored in the patch?
drug will be in solution or suspension in the matrix or reservoir
what are the advantages of transdermal drug delivery?
- avoids the GIT
- it has systemic effects
- no 1st pass metabolism
- there is controlled constant rate of delivery
- it has a long duration of action - up to 7 days
what are the disadvantages of transdermal drug delivery?
it can cause skin sensitisation / irritation
- patch may fall off
- not suitable for all drug
- appearance
- hair areas
what route of injection are vaccinations?
intramuscular
are IV injections O/W or W/O?
Oil in water
are IM injections O/W or W/O?
water in oil
what are some excipients in injections?
water for injection, preservatives, buffers, tonicity adjusting agents
rank the stability of solutions, suspensions, emulsions
solution>suspension>emulsion
what are the advantage of injections?
- they can have a local or systemic effect.
- used if oral route isnt suitable
- avoid the problems of the GIT
- no first pass metabolism
- rapid onset of action and prolong release
what are the disadvantages of injections
Invasive/painful
- patient could be scared of needles
- there is a risk of infection / embolism
- difficult to reverse effects
- difficult to adminster in some patient
can inhalers have local and systemic effects?
yes
what does actuation results in?
results in evaporation of propellant to form droplets to be inhaled into the lung?
how many actuation per inspiration in MDI’s?
one
what type of inhalers are used with spacers?
MDI
what do spacers do?
removes the need for co-ordination
what are some excipients for MDIs?
propellants, surfactants, co-solvents
what do co-solvents do in MDIs?
aid dissolution
how do dry powder inhaler work?
they are breath actuated
what type of inhalers don’t require propellants?
dry powder inhalers
do dry powder inhalers give larger doses?
yes
excipients of DPI:
carriers for the drug, pure drug
what are the advantages of inhalers
can use small doses, there are reduced systemic side effects, a fast onset of action, can use drugs with poor oral bioavailability
what are the disadvantages of inhalers
difficult technique, not suitable for all drugs, only 20% of drug reaches the lung, inflammation can reduce the size of the airways
