Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Use the oral syringe provided with your medication to measure and take your dose. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry. Sildenafil may cause side effects. The body takes longer to absorb it after a high-fat meal or alcohol. Remove the cap by pushing it down and twisting it counter-clockwise.Taking a counterfeit drug could put you at risk for harmful health effects. For information on making sildenafil more affordable, see the “Ways to reduce long-term drug costs” and . 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. 1 day ago · Both Viagra and sildenafil are available in mg, mg, and mg doses. REX MD currently has a out of 5-star rating on Trustpilot as of November About 84% of the over 3, reviews.