Proventil and ProAir are both inhalers that contain the same dosage of the same drug, albuterol, which is prescribed for respiratory conditions such as asthma and Chronic Obstructive Pulmonary Disease
(COPD), as well as for the prevention of respiratory symptoms experienced by some individuals after exercise or other forms of physical exertion. The only difference between the two is that they are made by different manufacturers. Proair is made by TEVA Pharmaceuticals, while Merck & Co. manufactures Proventil. If you have a prescription for albuterol that hasn't been specified "Dispense as Written" by your prescribing physician, your pharmacy may fill it with either Proventil or Proair, depending on what they have in stock. Sources: drugs.com, Drug Information Handbook (15th Edition, 2007-2008), and personal knowledge as a certified pharmacy technician.