Table 1: Major components, advantages, and disadvantages of inhaler devices.

InhalerFormulationMetering systemAdvantagesDisadvantages

pMDIDrug suspended or dissolved in propellant (with surfactant and cosolvent) Metering valve and reservoirPortable and compact
Multidose device
Relatively cheap
Cannot contaminate contents
Available for most inhaled medications
Contains propellants
Not breath-actuated
Many patients cannot use it correctly
High oropharyngeal deposition
pMDI + spacerEasier to coordinate
Large drug doses delivered more conveniently
Less oropharyngeal deposition
Higher lung deposition than a pMDI
Less portable than pMDI
Plastic spacers may acquire static charge
Additional cost to pMDI

BA-MDIDrug suspended in propellant Metering valve and reservoirPortable and compact
Multidose device
Breath-actuated (no coordination needed)
Cannot contaminate contents
Contains propellants
“Cold Freon’’ effect
Requires moderate inspiratory flow to be triggered

DPIDrug blend in lactose, drug alone, drug/excipient particlesCapsules, blisters, multidose
blister packs reservoirs
Portable and compact
Breath-actuated (no coordination needed)
Does not contain propellants
Requires a minimum inspiratory flow
May not appropriate for emergency situations
Many patients cannot use it correctly
Most types are moisture sensitive

SMI (Respimat)Aqueous solution or suspensionUnit dose blisters or
reservoirs
Portable and compact
Multidose device
High lung deposition
Does not contain propellants
Not breath-actuated
Not currently available in most countries
Relatively expensive

NebulisersAqueous solution or suspensionNebule dispensed into reservoir chamber of nebulizerMay be used at any age
No specific inhalation technique required
Vibrating mesh is portable and does not require an outside energy source
May dispense drugs not available with pMDIs or DPIs
Jet and ultrasonic nebulisers require an outside energy source
Treatment times can be long
Performance varies between nebulisers
Jet nebulisers cannot aerosolise a certain volume of solution
Risk of bacterial contamination
Newer nebulisers are expensive

pMDI: pressurised metered-dose inhalers; BA-MDI: breath-actuated metered-dose inhaler; DPI: dry-powder inhaler; SMI: soft mist inhaler.