A study conducted in Germany examined its effect on pulmonary and systemic blood systems and gas exchange parameters in patients with pulmonary arterial hypertension (PAH). Sixty PAH patients who underwent right heart catheterization (procedure to insert a thin plastic tube into an artery or vein in the arm or leg) received short-term nitric oxide inhalation and were subsequently given either sildenafil
, vardenafil, or tadalafil
. All three drugs caused significant pulmonary vasorelaxation, with maximum effects being obtained after 40 to 45 minutes (vardenafil), 60 minutes (sildenafil), and 75 to 90 minutes (tadalafil). Significant improvement in arterial oxygenation was only noted with sildenafil. Researchers assert that careful evaluation of each new drug, when being considered for PAH treatment, has to be undertaken.
Additionally, these drugs have the potential for significant drug interactions and should not be used if you are maintained on nitrates.