Patches, injections and inhalers Flashcards
Which two methods is transdermal drug delivery achieved by?
matrix
rate limiting membrane
The adhesive layer on a transdermal patch creates a _______ gradient and adheres to the skin
diffusion
What are the advantages of transdermal drug delivery?
bypass first pass metabolism
Systemic effects
controlled constant rate of delivery
long duration of action - up to 7 days
What are the disadvantages of transdermal drug delivery?
Can cause skin sensitisation patch may fall off not suitable for all drugs appearance hairy areas of skin
Injections may be freeze dried for reconstitution with water for injection. True or false?
True
Are intravenous injections o/w or w/o?
o/w
In an emulsion injection, what happens if the globule size is too large?
may cause an embolism
Are intramuscular injections o/w or w/o?
w/o
What are the advantages of injections?
Can be used for local or systemic effects
Bypass GIT and therefore first pass metabolism
Can be used if oral route not available
Rapid onset of action or prolong release
What are the disadvantages of injections?
Invasive/painful
Difficult to administer in some patients
Patients fear of needle
Risk of infection/embolism
In inhalers, the smaller the particle size the further down the respiratory tract the drug will penetrate. True or false?
True
What happens if the particle size of a drug in the inhaler is less than 1um?
The particle will be exhaled
What happens if the particle size of a drug in the inhaler is more than 10um?
Particle will remain in the oropharynx
What is the optimum size for drug particles in inhalers?
3-5um
In MDIs, actuation results in the _______ of propellent to form droplets to be inhaled into the lung
evaporation
What must a patient do to disperse the propellant and drug?
Shake the aerosol
What type of inhalers are spacers used with?
MDIs only
What are spacers used for?
Remove the need for coordination - children and infants must always be prescribed spacers with MDI
How do breath actuated inhalers work?
Inhalation triggers actuation of the device
What are the excipients for MDIs?
Propellant - gases at room temp are maintained as liquids under pressure in metal aerosol canister
Surfactants
Co-solvents
What are surfactants used for in MDIs?
To aid wetting of the suspension
What are co-solvents used for in MDIs?
To aid dissolution
Are propellants required in dry powder inhalers?
No
What are the excipients for DPIs?
Carrier for the drug e.g. lactose
Pure drug
MDIs are more stable than DPIs. True or false?
True - because of packaging, DPIs are susceptible to moisture degradation
What are the advantages of inhalers?
Can use small doses Reduced systemic side effects Fast onset of action Can use drugs with poor oral bioavailability MDIs are cheap
What are the disadvantages of inhalers?
Difficult technique Not suitable for all drugs Only 20% of drug reaches the lungs Inflammation can reduce the size of the airways Cost of DPI
