Arnuity Ellipta is a corticosteroid. The drug functions by preventing the release of substances in the body that are known to cause inflammation. Arnuity Ellipta is used in treating asthma patients and to prevent asthma attacks. It is important to note that this drug cannot treat an asthma attack that has already begun. It is also important that patients inform their physicians if they have been sick or have had an infection of any kind since the patient may not be able to use Arnuity Ellipta until they are well.