page_title: Metered-dose inhaler
section_title: Propellants
hierarchical_section_title: Metered-dose inhaler / Propellants
caption_attribution_description: English: Cipla CFC-free inhaler (Generic Ventolin)
context_page_description: A metered-dose inhaler is a device that delivers a specific amount of medication to the lungs, in the form of a short burst of aerosolized medicine that is usually self-administered by the patient via inhalation. It is the most commonly used delivery system for treating asthma, chronic obstructive pulmonary disease and other respiratory diseases. The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of both for the treatment of asthma and COPD. Other medications less commonly used but also administered by MDI are mast cell stabilizers, such as cromoglicate or nedocromil.
context_section_description: One of the most crucial components of a MDI is its propellant. The propellant provides the force to generate the aerosol cloud and is also the medium in which the active component must be suspended or dissolved. Propellants in MDIs typically make up more than 99% of the delivered dose, so it is the properties of the propellant that dominate more than any other individual factor.  This is often overlooked in literature and in industry because so few propellants are used and their contribution is often taken for granted.  Suitable propellants must pass a stringent set of criteria, they must:
  have a boiling point in the range -100 to +30 °C 
  have a density of approximately 1.2 to 1.5 g cm⁻³ (approximately that of the drug to be suspended or dissolved)
  have a vapour pressure of 40 to 80 psig 
  have no toxicity to the patient 
  be non-flammable 
  be able to dissolve common additives (active ingredients should be either fully soluble or fully insoluble)
caption: CFC-free Asthalin HFA inhaler
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