Phosphodiesterase 4 inhibitors in chronic obstructive pulmonary disease: a new approach to oral treatment

Chronic obstructive pulmonary disease represents a major global health care burden for both primary and secondary care providers and is the most common respiratory condition necessitating hospital admission. Short-acting bronchodilators play a vital role in immediate relief of symptoms, while inhaled long-acting bronchodilators and inhaled corticosteroids are advocated for regular use in individuals with persistent symptoms and exacerbations. Theophylline is a nonspecific phosphodiesterase inhibitor and is usually reserved for patients with ongoing symptoms despite optimum inhaled bronchodilator treatment or when difficulty is encountered with inhaler devices. However, it is often not widely used mainly due to frequency of dose-related adverse effects, numerous drug interactions and narrow therapeutic index. This in turn has lead to the development of more selective phosphodiesterase inhibitors in an attempt to create a drug which patients can use with beneficial effects but without the problems associated with theophylline. Current data do indicate that phosphodiesterase 4 inhibitors confer some benefits in chronic obstructive pulmonary disease when compared to placebo in terms of lung function, quality of life and exacerbations. They are also generally well tolerated. Further studies are required to determine fully their long-term beneficial and adverse effect profiles and ultimately where they might comfortably sit in management algorithms.