Why can't beclovent (beclomethasone) be used to stop an asthma attack when it is already in progress?

Not a bronchodilaor: Ceclovent is a steroid and can be part of a program to control asthma, but it does not cause bronchodilitator and hence cannot stop an asthmatic attack whivh is caused by bronchoconstriction.

Because...: Steroid inhalers, like beclovent, (beclomethasone) are used to treat airway inflammation. Inflammation results from a cascade of events, involving many different cells, some of which take many, many hours to stop their effect. So, to control the inflammatory cascade, these inhalers need to be used all the time because they will take too long to have their desired effect during an acute episode.