Administration, Inhalation Adrenal Cortex Hormones--administration & dosage Adrenergic beta-Agonists--administration & dosage Albuterol--administration & dosage Asthma--diagnosis Delayed-Action Preparations--administration & dosage Dose-Response Relationship, Drug Drug Administration Schedule Drug Therapy, Combination Drug-Related Side Effects and Adverse Reactions Female Humans Male Needs Assessment Randomized Controlled Trials as Topic Respiratory Function Tests Risk Assessment Salmeterol Xinafoate Severity of Illness Index Survival Rate United States United States Food and Drug Administration