Patient description: A 39-year-old man came to the clinic with cough and shortness of breath that was not relieved by his inhaler. He had these symptoms for 5 days during the past 2 weeks. He doubled his oral corticosteroids in the past week. He is a chef with a history of asthma for 3 years, suffering from frequent cough, wheezing, and shortness of breath and chest tightness. The symptoms become more bothersome within 1-2 hours of starting work every day and worsen throughout the work week. His symptoms improve within 1-2 hours outside the workplace. Spirometry was performed revealing a forced expiratory volume in the first second (FEV1) of 63% of the predicted. His past medical history is significant for seasonal allergic rhinitis in the summer. He doesn't smoke or use illicit drugs. His family history is significant for asthma in his father and sister. He currently uses inhaled corticosteroid (ICS) and fluticasone 500 mcg/salmeterol 50 mcg, one puff twice daily.

Clinical trial eligibility criteria: eligible ages (years): 18.0-60.0,  Asthma History of physician-diagnosed asthma Methacholine PC20 less than or equal to 16 mg/ml and/or FEV1 improvement greater than or equal to 12% in response to 180 mcg albuterol Stable asthma for at least 6 weeks prior to study entry FEV1 greater than or equal to 60% of predicted result following 180 mcg albuterol Juniper ACQ score greater than or equal to 1.5 (optimal ACQ score cut-off point for asthma that is "not well-controlled" by NIH/Global Initiative for Asthma [GINA] guidelines) Nonsmoker (less than 10 pack-per-year lifetime smoking history and no smoking in the year prior to study entry) Able to perform spirometry, as per American Thoracic Society adherence with diary cards, fluticasone (monitored with Doser), and placebo pill trial (monitored electronically with Electronic Drug Exposure Monitor [eDEM] pill dose counter) for the final 2 weeks of the four-week run-in period At Visit 1, in steroid-naïve participants, no significant adrenal suppression, defined as a plasma cortisol concentration less than 5 mcg/dL. If adrenal suppression occurs, a 250 mcg corticotropin (ACTH) stimulation test will be performed. Plasma cortisol levels will be collected at baseline, and 30 and 60 minutes after the ACTH stimulation test. Participants must have a cortisol concentration greater than 20 mcg/dL on at least one of the post-ACTH time points Absence of bronchoscopy-induced exacerbation; if bronchoscopy-induced exacerbation has occurred, prednisone therapy must have stopped at least 6 weeks prior to study entry  Presence of lung disease other than asthma Presence of vocal cord dysfunction, due to potential confounding of ACQ score Significant medical illness other than asthma History of atrial or ventricular tachyarrhythmia Use of any medication that has a significant interaction with clarithromycin, including herbal or alternative therapies Asthma exacerbation within 6 weeks of the screening visit or during the run-in period prior to bronchoscopy Use of systemic steroids or change in dose of controller therapy within 6 weeks of the screening visit Inability, in the opinion of the study investigator, to coordinate use of dry powder or metered-dose inhaler or to comply with medication regimens Inability or unwillingness to perform required study procedures Prolonged heart rate corrected QT-interval (greater than 450 msec in women and greater than 430 msec in men) on echocardiogram (ECG) at study entry