If it is safe to do so, bronchodilators should be stopped before the test: 8 hours for short-acting beta-2 agonists, such as albuterol; 24 hours for ipratropium; 12 to 48 hours for theophylline; 48 hours for long-acting beta-2 agonists, such as salmeterol and formoterol; and 1 week for tiotropium.