Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension. This includes prescription or nonprescription over-the-counter [OTC] medicines and herbal or vitamin supplements. Different brands may not work the same way. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. In some patients, the use of VIAGRA with alpha-blockers can lead to a drop in blood pressure or to fainting medicines called HIV protease inhibitors, such as ritonavir Norvir , indinavir sulfate Crixivan , saquinavir Fortovase or Invirase , or atazanavir sulfate Reyataz some types of oral antifungal medicines, such as ketoconazole Nizoral and itraconazole Sporanox some types of antibiotics, such as clarithromycin Biaxin , telithromycin Ketek , or erythromycin other medicines that treat high blood pressure other medicines or treatments for ED VIAGRA contains sildenafil, which is the same medicine found in another drug called REVATIO. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. The following information includes only the average doses of this medicine.While completing my visa application, I signed the “Saudi Laws and Regulations” form that states: “I am fully aware that the crime of smuggling narcotics and other illegal drugs into . Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash. tingling in the arms, feet, legs, or hands. numbness in the arms, feet, legs, or hands. headache. diarrhea. heartburn. trouble differentiating between colors like blue and green. seeing a blue.