ABSTRACT
Introduction Apart from corpus cavernosum, phosphodiesterase (PDE) type-5 isoform is expressed in various other tissues, including the arterial and venous vasculature, the skeletal visceral and tracheobronchial muscles, the brain, the retina, and platelets. 1 The differential distribution of PDE-5 isoenzyme in various tissues, as well as the different selectivity of the pharmacologic agents, forms the basis for potential tissue-specific effects of PDE-5 inhibitors. Accumulation of data in this context has delineated the overall profile of actions of PDE-5 inhibitors, has expanded indications of use to include idiopathic pulmonary hypertension (specifically for sildenafil), and even shows potential for further therapeutic applications. It should be stressed, however, that although the three currently available agents show many similar modes of actions, an effect proven for one agent does not necessarily apply to the others. Furthermore, extrapolations of experimental evidence to the clinical setting should be made with caution.
