Ipratropium vs Tiotropium

2nd-Generation Antihistamines

Albuterol vs Salmeterol

Fluticasone & Budesonide

Montelukast & Zafirlukast

Zileuton

Omalizumab

Cromolyn & Nedocromil

Guaifenesin

Endothelin Receptor Antagonists (Bosentan)

Prostaglandin Analogs (Epoprostenol, Iloprost)