DPI Flashcards
what kind of inhalers are DPIs?
single dose inhalers- they do not contain a propellant
how do dry powder inhalers work?
as they do not contain a propellant they rely on the inhalation of the patient to carry and inhale the drug
what was an aerohaler?
an inhaler that was designed for nasal inhilation
what was pressent in an aerohaler?
isoprenaline- b adrenoceptor agonist which caused bronchodilation
problem- poor deposition so no longer used
what was a Spinhaler (Fisons)?
an old oral inhaler
it contained Disodium cromoglicate
drug was in capsule and was ineserted into devise
and there was a fan present to deaggregate powder
what was Rotahaler(Allen and Hanburys)?
Oral Salbutamol Beclometasone Phased out 1990s
how much of the drug reaches the deep lung area?
20%
why would there be residual powder left in the device?
due to either inefficient delivery or adhesion to polymer surfaces
what are the problems associated with DPI design?
- residual powder left in the device, due to either inefficient delivery or adhesion to polymer surfaces
- inefficient separation of the coater-carrier complex (or agglomerated drug in case of Turbohaler)
- agglomeration of the drug either before or after separation
how in this design do they increases volume of dose, enhances flow and reduces drug agglomeration?
usually the micronised drug mixed with ‘carrier’ excipient
how must drug be deglomeruated?
by sheer forces during inhilation
what is airflow rate through the inhaler determined by?
airflow rate through inhaler is determined by the intrinsic resistance to airflow through the device
•dependent on inspiratory effort of user – greater effort, higher PIFR (peak inspiratory flow rate) through the device•lower resistance devices will give higher PIFR than higher resistance devices
what are the types of single dose DPIs?
spininhaler/ rotahler/ aerooliser
what is an example of a multipile dose inhaler?
Accuhaler(GSK) – salbutamol, salmeterol, fluticasone and combinations. Moulded plastic, approx8.5 cm diameter
what is the function of the multiple dose inhaler device?
device has 2 functions: delivery of dose and storing the empty foil strip (base foil and peeled lid foil)
how mant doses would be in an accuinhaler?
60
what is a Turbohaler?
100 or 200 metered doses of terbutaline, formoterol, budesonide & combinations
•pure drug, micronized particles spheronized into aggregates approx0.5 -1 mm diameter
how do you load a turbohaler?
o load, hold upright & twist the base – scraper ensures holes not overfilled i.e. dose governed by volume of holes
•on inhalation, most air enters via by-pass holes under mouthpiece, but some passes through dosing disk and carries drug to mouthpiece
•spiral channels in mouthpiece develop turbulence which breaks up agglomerates
•dessicantneeded for terbutaline
what are the advantages and limitations of DPIs?
ease of use– generally, DPIs easier to use than pMDIs. Easier to co-ordinate inhalation with drug delivery since breath actuated. • however breath-actuated pMDIsand spacer devices help overcome co-ordination issues with pMDIs• however, single dose DPIs not as convenient as multiple dose inhalers •no propellant– may cause cough, adhesion and stability issues. Environmental issues.
lack of additives– many DPIs use lactose as excipient. Turbohalerhas no excipients - lack of sensation since dose small• pMDIscontain propellants, surfactants (oleic acid – bronchospasm), co-solvents•dose counters–major compliance aid. • pMDIs– difficult and expensive for dose counters
Oropharyngealeffects– e.g. oral candidiasis –generally less with DPIs compared to pMDIs(up to 90 % of dose, but reduce with spacers)•inspiratory flow– performance of DPIs depends on PIFR through device and rise time to peak. Studies have shown adults with severe asthma can still generate suitable PIFRs and rise times to generate dose.
spacer devices– only used with pMDIs•humidity– dry powders may be affected by moisture and become less efficient. Must not exhale into devices.
