Cromolyn is a mast cell stabilizer. In vitro and in vivo animal studies have shown that cromolyn sodium inhibits the degranulation of sensitized mast cells, which occurs after exposure to specific antigens. Cromolyn sodium acts by inhibiting the release of histamine and SRS-A (slow-reacting substance of anaphylaxis) from the mast cell. Cromolyn is indicated in the management of patients with mastocytosis, prophylaxis (long-term control) of bronchial asthma, prevention of exercise-induced bronchospasm, prevention and treatment of seasonal and perennial allergic rhinitis The most frequently reported adverse reactions attributed to cromolyn sodium treatment were: throat irritation or dryness, bad taste, cough, wheeze, nausea.

Reproterol is a short-acting β2 adrenoreceptor agonist used in the treatment of asthma. Reproterol increases the generation of cAMP in isolated peripheral blood monocytes in vitro more effectively than does orciprenaline. In the presence of the highly potent but nonselective ß-antagonist, propranolol, the cAMP-generating action of reproterol was inhibited only partially. Reproterol has gained wide use when it was licensed as a fixed combination therapy with cromoglycate. Until today, the bronchodilator effects of reproterol and the bronchoprotective and anti-inflammatory actions of cromoglycate combined in one inhaler remain the successful fixed combination of a disease-modifying and symptomatic drug for the treatment of asthma.

Levalbuterol is the (R)-enantiomer of the drug substance racemic albuterol (salbutamol). Binding studies have demonstrated that (R)-albuterol binds to the beta2-adrenergic receptor with a high affinity, whereas (S)-albuterol binds with 100-fold less affinity than (R)-albuterol. Other evaluations have suggested that (R)-albuterol possesses the bronchodilatory, bronchoprotective, and ciliary-stimulatory properties of racemic albuterol, while (S)-albuterol does not contribute beneficially to the therapeutic effects of the racemate and was originally assumed to be inert. Xopenex (levalbuterol HCl) Inhalation Solution is indicated for the treatment or prevention of bronchospasm in adults, adolescents, and children 6 years of age and older with reversible obstructive airway disease.