Which medication is NOT an oral systemic corticosteroid?

Formoterol is the correct choice as it is not an oral systemic corticosteroid. Instead, it is a long-acting beta-agonist (LABA) used primarily in the management of asthma and chronic obstructive pulmonary disease (COPD) for bronchodilation. LABAs like formoterol work by relaxing the muscles around the airways, making breathing easier, but they are not corticosteroids.

In contrast, the other options—prednisolone, methylprednisolone acetate, and prednisone—are all corticosteroids used to reduce inflammation within the body and are available in oral formulations. Prednisolone and prednisone are commonly prescribed to treat various inflammatory conditions, including asthma exacerbations. Methylprednisolone acetate, while often administered via injection, can also have systemic effects similar to oral corticosteroids when used in certain formulations. Hence, formoterol stands out as the only non-corticosteroid medication among the choices provided.