Patients should always ask their doctors for medical advice about adverse events. Although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels. Box , Mission, KS If your pharmacy does not participate, you may be able to submit a request for a rebate in connection with this Savings Offer. 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 have an erection that lasts more than 4 hours, get medical help right away. The major circulating metabolite results from N-desmethylation of sildenafil, and is itself further metabolized. Before starting, stopping, or changing any medications while taking sildenafil, please get the advice of your doctor or pharmacist.Side Effects. Dizziness, headache, flushing, or stomach upset may occur. Vision changes such as increased sensitivity to light, blurred vision, or trouble telling blue and green colors apart may. AdFind the lowest available Sildenafil prices in your area. No sign-up required. Save now! Search & compare local Sildenafil prices. Save up to 80% on Sildenafil instantly!More: HELP · How It Works · FIND A PHARMACY. AdDon’t go to the pharmacy without checking prices at GoodRx® first. No commitment or fees. Find the lowest price in your neighborhood & use our free coupons to save up to 80%5-Star Reviews · No Credit Card Required · Over 70k Pharmacies · No Insurance Required””GoodRx can help you save, whether you have insurance or not.”” – Patch.