The active component of MAXAIR AUTOHALER (pirbuterol acetate) is (R,S)a6-{[(1 ,1 -dimethylethyl)amino] methyl}-3-hydroxy-2,6-pyridinedimethanol monoacetate salt, a beta-2 adrenergic bronchodilator.

Pirbuterol acetate is a white, crystalline racemic mixture of two optically active isomers. It is a powder, freely soluble in water, with a molecular weight of 300.3 and empirical formula of C₁₂H₂₀N₂O₃†C₂H₄O₂.

MAXAIR AUTOHALER is a pressurized metered-dose aerosol unit for oral inhalation. It provides a fine-particle suspension of pirbuterol acetate in the propellant mixture of trichioro-monofluoromethane and dichlorodifluoromethane, with sorbitan trioleate. Each actuation delivers 253 mcg of pirbuterol (as pirbuterol acetate) from the valve and 200 mcg of pirbuterol (as pirbuterol acetate) from the mouthpiece. The unit is breath-actuated such that the medication is delivered automatically during inspiration without the need for the patient to coordinate actuation with inspiration. Each 14.0 g canister provides 400 inhalations and each 2.8 g canister provides 80 inhalations.

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