- Paper Report
- Open Access
Sildenafil (Viagra), hemodynamics and the lung
- Rubin Cohen1
© Biomed Central Ltd 2001
- Received: 3 April 2001
- Published: 14 September 2001
- Phosphodiesterase inhibitors, pulmonary circulation, vasodilator therapy
Pulmonary hypertension (PHT) is a disease that carries a high mortality. The only presently available treatments apart from administration of oxygen, are nitric oxide administration and lung transplantation. Vasodilators (for example calcium channel blockers) are not selective for the pulmonary circulation, as they lower mean pulmonary arterial pressure (MPAP), mean systemic arterial pressure (MAP), and cardiac output (CO).
The aims of this study were to examine the effects of sildenafil (Viagraa) on hemodynamics and pulmonary gas exchange in a porcine model. Sildenafil is a selective oral phosphodiesterase-V (PDE-V) inhibitor and is presently used to treat male impotence. PDE-V is present in high concentrations not only in the corpora cavernosa, but also in vascular, tracheal and visceral smooth muscles. Inhibition of this enzyme leads to increased cGMP, which results in vascular relaxation. Dipyridamole is also an inhibitor of PDE-V, albeit a nonselective one.
Low normal and high doses (25, 50 and 100 mg respectively) of sildenafil depressed the partial pressure of arterial oxygen PaO2 most likely through increased intrapulmonary shunt flow. CO was increased, MAP was reduced, and MPAP decreased after high dose (100 mg).
Porcine model, nasogastric administration, hemodynamic measurements, multiple inert gas elimination technique