The global pharmaceutical giant Pfizer has been given the go ahead this week by the European Commission for its drug, Revatio, to be used by children aged 1 to 17 in the treatment of Pulmonary Arterial Hypertension. Revatio was approved for use by adults in June 2005. Pulmonary Arterial Hypertension (PAH) also known as high blood pressure of the lungs is a serious disease of the pulmonary arteries which connect the lungs to the heart. Normally, venous blood is pumped through the lungs by the right atrium and right ventricle of the heart. However, when PAH occurs the blood flow through the pulmonary arteries is restricted putting the right side of the heart under increasing pressure to pump blood through to the lungs. The results can include shortness of breath, dizziness, fainting, all of which are exacerbated by exertion, and heart failure. Revatio works by relaxing the arterial wall, leading to decreased pulmonary arterial resistance and pressure and thus allows blood and oxygen to flow more freely. This, in turn, reduces the workload of the right ventricle of the heart and improves symptoms of right-sided heart failure. Revatio contains sildenafil which is the same medicine used in Pfizer’s big selling erectile dysfunction drug Viagra. Sildenafil is a PDE-5 inhibitor and as PDE-5 is primarily distributed within the arterial wall smooth muscle of the lungs and penis, sildenafil acts selectively in both these areas without increasing blood flow or reducing blood pressure in other areas of the body. Cara Cassino, vice president of Pfizer Medicines Development Group, noted that PAH "is a rare, devastating disease that can affect children" and with the approval of Revatio, "these young patients now have an important treatment option that may help manage their condition". The approval "is another example of our ongoing commitment to rare diseases", Dr Cassino added.