- Current use of any systemic or inhaled immunosuppressive drugs, including systemic and inhaled corticosteroids (topical corticosteroids are permitted), long-acting β2 agonists, leukotriene antagonists, cromolyn sodium, nedocromil sodium, theophylline or any inhaled or systemic medication for asthma other than short-acting β2 agonists, for at least 4 weeks prior to study drug administration on Study Day 0.