Bioequivalence and Bioavailability Forum

Dear Mahesh M,

❝ Can anyone suggest me what are the reasons for maintaining 30 sec gap between two inhalation (Puffs) in MDIs formulation? (Mentioned in SPC or PI)

Inhaling consistently and correctly sounds like a trivial task but is in fact quite difficult. Especially when multiple inhalations are needed. A 30sec interval between any two inhalations adds some reassurance and is likely good for the efficacy. For the clinical staff it is a great help too that they don't need to rush every inhalation through. As you will see when you start the study 30secs is not a lot in practice.

❝ And if we maintained the 30 sec gap between two puffs then chances miss to characterize the initial rate of absorption of the drug and the peak concentrations.

Yes, if you are working on e.g. Formoterol or Salmeterol MDI then you'll find it difficult to capture the Cmax properly. You will sometimes see it on the first blood sample. There is no good way around it, for example you can't just ask the clinical to "work faster", so you'll have to live with it.