It works for up to 36 hours. 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. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. Such patients must not apply any out-of-pocket expenses incurred using this Savings Offer toward any government insurance benefit out-of-pocket spending calculations, such as Medicare Part D true out-of-pocket TrOOP costs You are responsible for reporting use of this Savings Offer to any private insurer, health plan, or other third party who pays for or reimburses any part of the prescription filled using this Savings Offer, as may be required. The company loses tens of millions of dollars to the counterfeit drug trade each year, a Pfizer spokesman said.Pfizer fights fake Viagra with RFID. Drug maker release details of high-tech plan to ensure its most frequently counterfeited product is the real thing. Photo: Viagra RFID takes aim . The study found that about 80 percent of these pills were counterfeit, and while the fake Viagra pills contained the active ingredient, sildenafil citrate, the amount was only 30 . Viagra, Cialis most popular fakes seized. John P. Leonard is the No. 2 trade official at Customs and Border Protection. U.S. Customs and Border Protection. A year veteran .