Use of inhalers (Drugs and drug delivery) Flashcards
How much of the drug is delivered with good inhaler technique (and how much with poor?)
- 20-50% with good inhaler technique
- 5% with poor inhaler technique
What other factors contribute to poor drug delivery?
- Large drug particles; deposited at the back of the throat/pharynx (oropharynx)
- Speed breathing in; has to be at the right pace so drug particle does not hit throat
What are the advantages of pMDIs (pressurised metered dose inhaler)?
- Compact
- Portable
- Multidose delivery
- Suitable for emergency
What are the disadvantages of pMDIs?
- Requires co-ordination
- High oropharyngeal drug deposition
- Difficult to determine remaining dose
What are the advantages of breath-actuated MDIs?
- No co-ordination issues as per pMDIs
does not require co-ordination of device and inhalation
What are the disadvantages of breath-actaued MDIs?
- Requires sufficient inspiratory flow to trigger the device
What are the counselling points for pMDIs?
- Shake (gently) before use (so propellent and drug are sufficiently mixed)
- Spray inhaler one or twice to prime device
- Take normal breath in, out, and then…
- Take breath in, SLOWLY, GENTLY AND DEEPLY
(“device produces aerosol for you so you don’t need to do the hard work”) - Hold breath for as long as is comfortable (gravity allows drug deposition in airways)
- Leave about a minute between puffs (ensuring adequate drug/propellent is expelled; pressure issues with over-use = less drug sprayed out)
What are the advantages of DPIs (dry powder inhaler)?
- Breath actuated (instead of finger)
- Less co-ordination required
- Compact (like pMDI)
- Portable (like pMDI)
- Higher lung deposition of drug than pMDI
What are the disadvantages of DPIs?
- Poor efficacy if insufficient inhalation
- Need to prime dose (twist bottom/pierce capsule etc) each time
- Most are MOISTURE SENSITIVE (counselling point; do not keep in bathroom cabinet etc)
What are the counselling points for a DPI?
- Shake before use
- Prime device (twist bottom/pierce capsule)
- Inhale and exhale normally..
- Breathe in forcefully, hardly and deeply
(dry powder clumps together; powerful inhalation required to aggregate the particles)
What are spacers, their advantages and why are they used?
- Removes need for coordination; tidal breathing is effective (taking several breaths giving a couple of seconds to inhale the drug)
- Reduces risk of oral infection (thrush) from ICS
- Suitable for managing mild/moderate acute asthma/COPD
- pMDI w/spacer equivalent to nebuliser
What are nebulisers and when are they used?
- Vaporised/mist drug inhaled via a mask through a machine
- Used when distressing/disabling breathlessness is present despite maximum inhaler therapy
- Used mainly in hospitals (less education and cooperation required)
What are the disadvantages associated with nebulisers?
- Low efficiency (about 10% of drug reaches lungs)
- Susceptible to microbiological contamination (replace mouthpiece/tubing ever 3-4 months, wash w/warm water and detergent and dry overnight with normal use)
What are SABAs and what do they do?
- Short acting beta2 agonists
- Reduce breathlessness
- RELIEVER/rescue medication (does not prevent/control airway inflammation > preventer)
What adverse effects are associated with SABAs/LABAs?
- Tachycardia due to action on beta-1 adrenoceptors in the heart
- Tremor and muscle cramp; action on beta-2 adrenoceptors in the skeletal muscle
- Results in potassium uptake thus potentially hypokalaemia (beware of patients on nebuliser for extended time)
