The manufacturer has warned emergency physicians of this dangerous side effect in an effort to avoid the possibility of giving nitroglycerin to a patient with chest pain who presents to the emergency department after taking sildenafil. Paramedics across the country have also been cautioned to ask men with chest pain if sildenafil has been taken before they administer sublingual nitroglycerin. Recreational drugs such as amyl nitrite ("poppers") are thought to have the same hypotensive effect when combined with sildenafil. One of the forms of phophodiesterase is termed PDE5. The prescription PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are prescription drugs which are taken orally. They work by blocking the action of PDE5, which causes cGMP to degrade. CGMP specific phosphodiesterase type 5 causes the smooth muscle of the arteries in the penis to relax, allowing the corpus cavernosum to fill with blood. free samples viagra canadian pharmacy viagra for sale What better, Viagra or Cialis? 25mg viagra online without prescription buy Viagra 150mg here buy viagra online without prescription Staphysagria Impotence due to feelings of being shy or embarrassed Quiet in disposition Commercially, Caverject is available in doses of 10-20 mcg, but a number of pharmacists and physicians prepare PGE1 in doses appropriate to the individual patient.