This medicine works best when you take it on an empty stomach an hour before sex. Especially tell your healthcare provider if you take any of the following: medicines called nitrates medicines called guanylate cyclase stimulators such as Adempas riociguat medicines called alpha-blockers, such as Hytrin terazosin HCl , Flomax tamsulosin HCl , Cardura doxazosin mesylate , Minipress prazosin HCl , Uroxatral alfuzosin HCl , Jalyn dutasteride and tamsulosin HCl , or Rapaflo silodosin. These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. They include dutasteride Avodart, Jalyn and finasteride Propecia, Proscar. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil. Medicines that you take by mouth are called oral medicines.Most popular Safeway $ retail Save 94% $ Get free savings Low price Walgreens $ retail Save 94% $ Get free savings directions Closest store Rite Aid. Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that . If you’re interested in buying Viagra online, five of the best options available are Hims, Roman, Lemonaid, Optum Store, and REX MD. Read on for full details on the process .