Can beclovent (beclomethasone) be used to stop an asthma attack in progress?

No: Beclovent is an inhaled corticosteroid which is very effective in reducing inflammation in the airways, but is not a bronchodilator as albuterol is. Inhalers such as ventolin hfa, proventil hfa, pro-air hfa, xopenex (levalbuterol) hfa should be used for acute asthma attacks and open up the airways within minutes to allow you to breathe much easier.

Maintenance: I agree, beclovent is what we call a maintenance medication, it can take weeks to reach full affect. You need a "rescue" or short acting medication like nebulized albuterol, or what they call metered dose inhalers ("puffers"/inhalers) like proventil, proair maxair, ventolin or xopenex (levalbuterol) for quick relief.

NO...: There are basically 2 classes of meds for asthma: relievers and controllers. Only relievers, like albuterol, can stop an asthma exacerbation. Beclovent, (beclomethasone) a steroid inhaler, is a controller medication and decreases airway inflammation over a period of time and will not acutely stop an asthma exacerbation. It helps chronically.