Both Viagra and its generic version contain the same active ingredient, sildenafil citrate, and are similar in effectiveness and side effects. The primary difference is cost; generic Viagra is less expensive. Both are available in doses of 25 mg, 50 mg, and 100 mg. Some men may prefer the branded version despite the higher price. 

Sildenafil citrate, found in Viagra, generic Viagra, and sildenafil, typically starts working within 30 minutes to an hour and lasts about four hours. Tadalafil, the active ingredient in Cialis and its generics, starts working within 30 minutes to two hours and can last up to 36 hours, offering a longer duration of effect. 

It is recommended not to take ED medication more than once in a 24-hour period. 

ED medications do not cause an automatic erection; sexual arousal or stimulation is still necessary. These medications facilitate the erection process when aroused. 

While oral ED medications are highly effective, they might not work for everyone. Roman currently offers only ED medications, but other options include lifestyle changes like exercise, diet adjustments, quitting smoking, and limiting alcohol, as well as surgical interventions and devices like penile vacuum pumps. 

ED medications do not directly influence libido. However, achieving stronger erections might boost confidence, potentially increasing desire and eagerness for sexual activity in some men.