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Is an asthma inhaler (MDI) an example of vaporization?

  1. Mar 5, 2015 #1
    I am trying to give some context to medical vaporizers in a literature review I am composing and initially decided to give asthma inhalers and nasal inhalers as examples.
    I realised however, that some sources on-line were referring to these metered dose inhalers as vaporization devices when they are in fact dispensing an aerosol rather than a vapour.

    I understand the nasal inhaler to be a good example of evaporation and therefore vaporization.Though the label of a vaporizer applied to an MDI inhaler still seems problematic.

    This quote (from The Mechanics of Inhaled Pharmaceutical Aerosols: An Introduction, but taken from Wikipedia) implied it may be somewhat accurate to propose that an asthma inhaler is using the process of vaporization for drug delivery : "Breakup of the volatile propellant into droplets, followed by rapid evaporation of these droplets, results in the generation of an aerosol consisting of micrometer-sized medication particles that are then inhaled"

    The quote suggests that the evaporation of the atomized droplets is generating an aerosol.
    I am struggling to understand how the inhaler is not a vaporization device - as it produces an aerosol, but this aerosol is produced from the evaporation of droplets of propellant and is therefore a device used for the transformation of phase from liquid to gas i.e a vaporizer.

    What is the general consensus on this?

    I will likely avoid the inclusion of the asthma inhaler as an example of a common vaporization device in my lit review if this level of confusion will be present in the mind of the examiners marking it.

    I have discussed anaesthetic vaporizers then moved onto explain that vaporization as a method of pharmaceutical delivery is more common than it first appears, thus the context of my question is my attempt to show the viability and popularity of vaporization for pulmonary delivery of medicines.
    Also I would be interested if anybody could suggest any other common, but not necessarily obvious examples of vaporization devices used for medical purposes or other favourable applications (by favourable, i mean..... not cannabis vaporizers - my institution of academia seems to frown heavily on that particular application).

    Thanks for reading, any input or information is greatly appreciated.
  2. jcsd
  3. Mar 5, 2015 #2


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    "Solids, liquids, and gases" --- plus sols, gels, emulsions --- ta-da, ta-da, ta-da. Three phases at equilibrium. The rest of the "gray" area are non-equilibrium situations, meta-stable states, whatever you will. An aerosol is not a vapor, and it's not a liquid, nor is it at equilibrium. You might dig around in Adamson's Physical Chemistry of Surfaces for some sense of what is and is not happening. Probably a good item to have in a review.
  4. Mar 7, 2015 #3


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