Why should you use bronchodilator before corticosteroid?

Old idea: This is an old idea, that you should open up the constricted airways with a bronchodilator before taking your corticosteroid inhaler, so the medication can get deeper into your lungs. But the reality is that if you use your steroid inhaler regularly, as prescribed, you can control the inflammation to the point that you don't have any bronchospasm, and don't have to use your albuterol first.

The BD works fast!: You did not say the condition being treated, but by the combination of drugs, it sound like an asthmatic condition. Bronchodilators open up the bronchioles immediately, while the inhaled steroids work longer, but do not work immediately. Combinations like this work well for most. Good luck!