While Viagra is a helpful treatment for impotence, Cialis is another type of medication which helps overcome the inconvenience of erectile dysfunction. Cialis is also known as Tadalafil. Cialis works similarly to Viagra in the sense that it also allows for blood to flow to the penis. Cialis taken ones a day results in gaining a faster and easier erection however, the side effects of Cialis include muscle pains, headache and back pain. While Cialis is a very useful product, there are some patients suffering from impotence who do not feel comfortable buying it over the counter. Levitra is a round orange pill which helps prompt an erection. Levitra relaxes the blood vessels in the penis to cause the penis to react after sexual stimulation. Levitra is usually only effective 25-60 minutes after you take it. Levitra can be taken after eating or drinking, meaning that food and even alcohol won’t affect the potential of Levitra.