Combination therapy appears promising for patients who are refractory to treatment or whose disease progression is not well controlled with monotherapy. An optimal combination drug therapy regimen remains debatable and should be customized for individual PAH patients. Further studies are needed to determine the optimal combination therapy in PAH based upon efficacy, safety and cost.

Ambrisentan is an effective and safe treatment which is, in the authors' opinion, a valuable addition to the armamentarium against PAH. Ambrisentan offers a relative lack of drug interactions, once daily dosing and reassuring liver safety, offering safety and convenience advantages over bosentan. Presently, there is a lack of comparative studies between PDE5 inhibitors and endothelin receptor antagonists and a lack of data comparing bosentan with ambrisentan. This is hindering data-based conclusions regarding relative efficacy and further studies are needed to define the role of ambrisentan in the management of PAH.

Pulmonary arterial hypertension (PAH) is a progressive disease that causes severe disability and has no cure. Over the past 20 years, a variety of treatment options have evolved for the management of PAH. With an expanded therapeutic armamentarium come more complex decisions regarding treatment options. Agent selection depends upon several factors including efficacy, side effect profile, and cost, as well as convenience of administration. We have undertaken a review of phosphodiesterase-5 (PDE-5) inhibitors in PAH with a focus on efficacy and safety. A literature search was conducted using the Medline and Cochrane Central Register of Controlled Trials databases (1966–February 2010) for relevant randomized clinical studies. Overall, 10 studies met our inclusion criteria. Sildenafil was the most commonly studied agent, followed by tadalafil and vardenafil. Most trials found that the PDE-5 inhibitors significantly improved exercise capacity and lowered pulmonary pressures. However, there were conflicting results regarding these agents’ impact on improving cardiac function and functional class. Overall, these medications were effective and well tolerated with a relatively benign side effect profile. The PDE-5 inhibitors are an important option in treating PAH. While most of the published clinical data involved sildenafil, the other PDE-5 inhibitors show promise as well. Further studies are needed to determine the optimal doses of this therapeutic drug class, as well as its effects as adjunctive therapy with other agents in PAH.