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)
What is the difference between a SABA and a LABAs onset of action?
SABA: Effective within 5 minutes or less, lasts for 4 to 6 hours.
LABA: Effective within 15-40 minutes, lasts for > 12 hours.
What are SAMAs and what do they do?
- Short acting muscarinic antagonists
- Antagonise ACh-mediated contribution to bronchospasm
- RELIEVER (smooth muscle relaxation)
What adverse effects are associated with SAMAs/LAMAs?
- Dry mouth
- Blurred vision
- Constipation
- Nausea
- Urinary retention
- Tachycardia
(Ipratropium blocks all muscarinic receptors without sub-type selectivity whilst M3 is main target)
What is the difference between SAMA/LAMA onset of action?
SAMA: 30 to 40 minutes, duration of action: 3 to 6 hours
LAMA: 1 - 2 hours, duration of action: 24 hours
What are LAMAs and what are their significance?
- Long acting muscarinic antagonists
- For patients who remain breathless despite short acting bronchodilators
- Tiotropium reduces exacerbations and hospitalisations (superior to ipratropium)
Why are corticosteroids used in asthma?
- Reduces airway inflammation (acts on eosinophilic inflammation as present in asthma)
- Regular use reduces exacerbations
- …ones
What adverse effects are associated with corticosteroids?
- Oropharyngeal candidiasis (inhaled)
- Adrenal suppression
- Osteoporosis
- Growth suppression
- Cataracts
- Glaucoma
- Pneumonia
What cautions are there between the ICS’ Clenil and QVAR?
Both are beclomethasone however QVAR is twice as potent.
When are leukotriene receptors antagonists used? (name one)
- Particularly useful in exercise-induced asthma
- Blocks the effect of leukotrienes
- E.g. Montelukast
What are the adverse effects associated with leukotriene receptor antagonists?
- Churg-Strauss syndrome
- Hepatic disorders
What is theophylline/aminophylline and what must be taken account with its use?
- Last line bronchodilator therapy
- Phosphodiesterase inhibitor (reduces histamine release)
- Clearance increased by smoking (higher dose req.)
- Clearances reduced in heart failure/liver disease/COPD (lower dose/more caution)
- Drug interactions
- Dose varies by brand
- Narrow therapeutic window
What adverse effects are associated with theophylline?
- Tachycardia
- Palpitations
- Nausea
- Headache
When is aminophylline used and how does it differ to theophylline?
- Theophylline given as IV (amine group increases solubility in water so drug does not precipitate in blood)
- Used in patients with near fatal asthma/life threatening acute asthma where poor response to initial therapy is seen
- MAY gain additional benefit
- Only used when failure to respond to other treatments
- Not effective in exacerbations of COPD
What factors decrease clearance of aminophylline?
- Cimetidine, ciprofloxacin, macrolides, O/C pill,
- Viral infection, heart failure, cirrhosis,
- Elderly
(reduce dose/use with caution)
What factors increase clearance of aminophylline?
- Carbamazepine, phenytoin, St. John’s Wort,
- Smoking, chronic alcholism
(increase dose)
When is magnesium sulfate used and what is its mode of action?
- For life threatening/near fatal asthma, acute w/o good initial response to inhaled bronchodilators
- Action: smooth muscle relaxation in vitro (weak bronchodilator)
- IV 1.2-2g over 20 minutes
What is the role of the pharmacist with asthma therapy?
- Accurate drug histories and medication reviews (wary of correct brand thus dose)
- Concordance; suitability and manageability of inhalers (combination?), patient understanding, inhaler technique
- Appropriate inhaler combination
- Stepping down and review inappropriate agents
- Steroid courses (and titrating down regimes)
- Antibiotic management
- Gastro/bone protection when on steroids (PPI/Ca2+)
- Management of steroid induced diabetes
- Theophylline levels
- Lifestyle advice; smoking cessation, weight management
