Larsmont-FA is a fixed-dose combination of 3 drugs Montelukast, Fexofenadine, and Acebrophylline.

Montelukast Sodium is the orally bioavailable monosodium salt of montelukast, a selective cysteinyl leukotriene receptor antagonist with anti-inflammatory and bronchodilating activities. Montelukast selectively and competitively blocks the cysteinyl leukotriene 1 (CysLT1) receptor, preventing binding of the inflammatory mediator leukotriene D4 (LTD4). Inhibition of LTD4 activity results in inhibition of leukotriene-mediated inflammatory events including migration of eosinophils and neutrophils; adhesion of leukocytes to vascular endothelium, monocyte, and neutrophil aggregation; increased airway edema; increased capillary permeability; and bronchoconstriction.

Fexofenadine

Fexofenadine is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.

Therapeutically Fexofenadine is a selective peripheral H1 blocker. It is classified as a second-generation antihistamine because it is less able to pass the blood–brain barrier and cause sedation, compared to first-generation antihistamines.

Fexofenadine is used for relief from physical symptoms associated with seasonal allergic rhinitis and for treatment of chronic urticaria.

Acebrophylline is a compound which has been found to act as a bronchodilating, mucoregulating and anti-inflammatory drug due to its components theophylline-7-acetate and ambroxol.

Theophylline-7-acetate, as with other xanthinic derivatives, has a bronchodilator effect due to inhibition of the intracellular phosphodiesterases, followed by an increase of adenosine monophosphate cyclic levels, which promote the relaxation of bronchial muscles.

Ambroxol modifies the mucous gel phase of secretions by decreasing the viscosity and increasing the serous gel phase. It increases the mucociliary clearance by stimulating cilia motility.