Pfizer formulated a medication they named 'Sildenafil Citrate'. It was invented as a medication for high blood pressure and angina but it was a real flop. The failure as a blood pressure medication was a blessing for the manufacture realizing that the men who possessed the samples refused to return it Pfizer delve a bit and realized they were onto something! So, they put it into a tablet, called it 'Viagra', and made $ millions.

Not to be caught flat footed, some clever researchers at Eli Lilly & co, (makers of Prozac amongst other things) and ICOS formed a joint venture called Lilly ICOS. They assayed samples of Sildenafil Citrate and experimented with ways to make it more effective. They hit the jackpot and called the chemical compound 'Tadalafil', and gave it the trade name Cialis.”

Since Cialis came later it was an improvement on the original-- the mother of all erectile dysfunction drugs – Viagra. It is a more effective and powerful product. It starts working up to twice as fast as Viagra and continues to work for between 24 to 36 hours, compared to Viagra's 6-8 hour effective life .In clinical tests Viagra, was found to work for 75% of people that tried it.

Under the same test conditions Cialis was found to work for 88% of men that tried it. Researchers claim it works twice as fast as Viagra with fewer side effects. In clinical studies Cialis helped 88 percent of men achieve erections in 30 minutes or less. The study also showed that Cialis continued to stay in the system for up to 24 hours!

Marketing analysis are already predicting that Eli Lilly & CO, the makers of Cialis, will hit at least US $600 million in sales within the first year. That has already put Pfizer into scrambling mode trying to develop campaigns to survive the shift in sales.

With the overwhelming success of Viagra and later Cialis Pharma companies do not want to be left behind. Men with E.D. (erectile dysfunction) have an option to choose what best suites their libido. One such product which is sold through many online pharmacies is Apcalis. Apcalis capsules are a generic form of Viagra, and sold through many online pharmacies. It claims to help men with erectile dysfunction problems achieve erections long enough to have intercourse, similar to Viagra.

While Apcalis rides piggyback on Viagra, Cialis has competition from Tadalis. Tadalis or Generic Cialis is used for the treatment of male impotence. The effectuality as well as the safety of Tadalis is equivalent to Cialis. The effect of the medication starts within 30 minutes and lasts for as long as 36 hours. Generic Cialis can help more people overcome erectile dysfunction because of its low cost.

No drug is free from side effects .Sexual enhancement pills needs all the more precaution. Consult your Doctor when on these pills. The most common side effects with Generic Cialis were headache, upset stomach, delayed backache or muscle ache. Although rare, men who experience an erection for more than 4 hours should seek immediate medical attention. Men should not drink alcohol in excess with Generic Cialis.