Which medication is considered a long-acting beta 2 agonist with a slow onset?

Salmeterol is classified as a long-acting beta 2 agonist (LABA) known for its therapeutic role in managing conditions such as asthma and chronic obstructive pulmonary disease (COPD). It operates by stimulating beta 2 adrenergic receptors in the airway smooth muscles, leading to bronchodilation. The key characteristic that defines salmeterol is its prolonged duration of action, which typically extends up to 12 hours, making it effective for long-term control of bronchospasm.

Additionally, salmeterol has a relatively slow onset of action when compared to short-acting bronchodilators. This slow onset is suitable for maintenance therapy rather than immediate relief of acute symptoms, differentiating it from medications like albuterol, which acts quickly.

The other medications listed do not align with the characteristics of a long-acting beta 2 agonist. Albuterol, for example, is a short-acting bronchodilator with a rapid onset. Dexamethasone is a corticosteroid that reduces inflammation but does not directly affect beta-adrenergic signaling. Dexmedetomidine is an alpha-2 adrenergic agonist used primarily for sedation in clinical settings and does not function as a bronchodilator.