Viagra, Levitra and Cialis are approved for use in the treatment of erectile dysfunction. All work by blocking an enzyme called PDE5. PDE5 is involved in holding blood in the penis, which creates an erection. A similar enzyme, PDE6, is involved in vision, especially color vision. The most common side effects of Viagra are headache and flushing. Many patients, especially those taking high doses of Viagra, will have changes to their eyesight including blurred vision and changes in color vision. These all go away in a few hours with Levitra and Viagra. They may last a bit longer with Cialis. There are some drug interactions to worry about. The most notable is the interaction between nitrates and these drugs that can cause very low blood pressure. Although people with coronary artery disease normally use nitrates, amyl nitrate (also known as poppers, liquid gold, stud and other colorful names) is used as a recreational drug. The combination of amyl nitrate and Viagra, Cialis or Levitra is likely to cause a big drop in blood pressure.
Viagra, Levitra and Cialis are too frequently used as "party drugs." For example, they are sometimes combined with club drugs like ecstasy (the combination is known as Sextasy). The danger is a higher likelihood of unprotected sex, increasing the risk of HIV and other sexually transmitted diseases.
