Antihistamines (histamine antagonist) block the action of histamine at the H1 and H2 histamine receptors.  Antihistamines that primarily block the H1 receptor are used to treat allergies.

Allergens interact with immune cells to cause the release of histamine, which binds to the H1 receptor on other cells to produce the symptoms of an allergic reaction.

Inhibition of histamine binding to target cells reduces allergic symptoms.

*Also contains Pseudoephedrine

No generic Leukotriene Receptor Antagonists are available.

The patent for Zafirlukast (Accolate) expires in 2011, and the patent for Montelukast (Singulair) expires in 2012.

Leukotriene antagonists block the inflammatory cascade by inhibiting the action of cysteinyl leukotrienes at CysLT1 receptors in bronchial smooth muscle and other tissues.

The action of leukotriene antagonists have been shown to improve asthma and seasonal allergy symptoms, reduce asthma exacerbations, and limit markers of inflammation such as eosinophil counts in the peripheral blood and bronchoalveolar lavage fluid.