Roflumilast is a drug which acts as a selective, long-acting inhibitor of the enzyme PDE-4. It has anti-inflammatory effects and is under development as an orally administered drug for the treatment of inflammatory conditions of the lungs such as asthma, and chronic obstructive pulmonary disease (COPD). Phosphodiesterase 4 (PDE4) is a member of the PDE enzyme superfamily that inactivates cyclic adenosine monophosphate and cyclic guanosine monophosphate, and is the main PDE isoenzyme occurring in cells involved in inflammatory airway disease such as chronic obstructive pulmonary disease (COPD). Although several experimental PDE4 inhibitors are in clinical development, roflumilast, a highly selective PDE4 inhibitor, is the first in its class to be licensed, and has recently been approved in several countries for oral, once-daily treatment of severe COPD.