Each of the following is an inhalant medication used to treat asthma EXCEPT:

Inhalant medications used to treat asthma primarily function by opening the airways and reducing inflammation in the lungs. Flovent is a steroid inhaler that helps decrease inflammation, while both Ventolin and Proventil are bronchodilators that provide quick relief of asthma symptoms by relaxing the muscles around the airways.

Dilantin, on the other hand, is an anticonvulsant medication primarily used to control seizures in conditions such as epilepsy. It is not indicated for the treatment of asthma and does not have properties that would directly benefit patients with this respiratory condition. Therefore, while the other medications listed are specifically designed to manage asthma symptoms, Dilantin does not have any therapeutic role in asthma treatment, making it the correct answer to the question.