DPI

Question 1

what kind of inhalers are DPIs?

Answer 1

single dose inhalers- they do not contain a propellant

Question 2

how do dry powder inhalers work?

Answer 2

as they do not contain a propellant they rely on the inhalation of the patient to carry and inhale the drug

Question 3

what was an aerohaler?

Answer 3

an inhaler that was designed for nasal inhilation

Question 4

what was pressent in an aerohaler?

Answer 4

isoprenaline- b adrenoceptor agonist which caused bronchodilation
problem- poor deposition so no longer used

Question 5

what was a Spinhaler (Fisons)?

Answer 5

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

Question 6

what was Rotahaler(Allen and Hanburys)?

Answer 6

Oral Salbutamol Beclometasone Phased out 1990s

Question 7

how much of the drug reaches the deep lung area?

Answer 7

20%

Question 8

why would there be residual powder left in the device?

Answer 8

due to either inefficient delivery or adhesion to polymer surfaces

Question 9

what are the problems associated with DPI design?

Answer 9

• 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

Question 10

how in this design do they increases volume of dose, enhances flow and reduces drug agglomeration?

Answer 10

usually the micronised drug mixed with ‘carrier’ excipient

Question 11

how must drug be deglomeruated?

Answer 11

by sheer forces during inhilation

Question 12

what is airflow rate through the inhaler determined by?

Answer 12

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

Question 13

what are the types of single dose DPIs?

Answer 13

spininhaler/ rotahler/ aerooliser

Question 14

what is an example of a multipile dose inhaler?

Answer 14

Accuhaler(GSK) – salbutamol, salmeterol, fluticasone and combinations. Moulded plastic, approx8.5 cm diameter

Question 15

what is the function of the multiple dose inhaler device?

Answer 15

device has 2 functions: delivery of dose and storing the empty foil strip (base foil and peeled lid foil)

Question 16

how mant doses would be in an accuinhaler?

Answer 16

60

Question 17

what is a Turbohaler?

Answer 17

100 or 200 metered doses of terbutaline, formoterol, budesonide & combinations
•pure drug, micronized particles spheronized into aggregates approx0.5 -1 mm diameter

Question 18

how do you load a turbohaler?

Answer 18

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

Question 19

what are the advantages and limitations of DPIs?

Answer 19

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.