Sildenafil may cause side effects. There were highly statistically significant improvements on the two principal IIEF questions frequency of successful penetration during sexual activity and maintenance of erections after penetration on VIAGRA compared to placebo. Men with untreated ED had relatively low baseline scores for all aspects of sexual function measured again using a 5-point scale in the IIEF. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity. According to the FDA, generic medications contain the same active ingredients as brand names, meaning there’s no difference in effectiveness or safety. Figure 6.Headache, flushing, and upset stomach are common Viagra side effects. These effects are usually mild and often resolve on their own. While rare, Viagra can cause an erection that lasts longer than 4 hours (priapism). This can result in permanent damage if left untreated. Vision changes are also possible. Save at least $5 per month on your prescription. Save at least $5 per month on your prescription. Call to get more information on how they can financially assist you with your prescription. You may be able to lower your total cost by filling a greater quantity at one time. Cut a higher-dosage pill in half to save 50% or more. The dose of Cialis you need will depend on whether you’re taking it daily or as needed. Daily doses are often between and 5 milligrams (mg). The as-needed dose is usually 10 mg but can range from 5–20 mg. The typicaldose of Viagra is 50 mg. However, the dosage can range from 25– mg.