Follow the manufacturer’s directions to use and clean the oral syringe. 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. If you are taking sildenafil for PAH, take the missed dose as soon as you remember it. If you prefer, you may contact the U. Ask your pharmacist for a list of the ingredients.Sildenafil is a generic drug, which is an exact copy of the active drug in a brand-name medication. The generic is considered to be as safe and effective as the original drug. And generics tend to. Viagra should be taken at 25 mg per 48 hours in order to be used safely along with this drug, since ritonavir increases the concentration of Viagra. CYP3A4 inhibitors. Viagra should be taken at Rev. 5/1/20 Value-Priced Medication List Price may be as low as: In addition to discounts on thousands of brand-name and most generic medications, members get even more .