Pharmaceutical companies are pushing new versions of drugs to treat erectile dysfunction and enhance sexual performance in Mexico and using the country as a test market. Pfizer launched a chewable version of its pioneering Viagra exclusively in Mexico last year; Eli Lilly debuted a daily dosage of its Cialis in early 2011.

Why the special interest in Mexico?

“The market is very big,” said Alejandro Triulzi Garciadiego, manager of Lilly ICOS, the division that sells Cialis in Mexico.

And — although Mexico is already a major market for Cialis, Viagra and Bayer’s Levitra – Mexico’s potential appears barely tapped.

Erectile dysfunction affects an estimated 6 million men in Mexico, but only 15 percent have sought treatment, according to a recent Eli Lilly study.

And, according to the study, sex happens to be even more important for Mexicans, on average, than the rest of the world. Fifty-six percent of Mexicans over age 33 have sex an average of 2.03 times per week. The country ranked second only to Portugal, where the frequency is 2.05 times weekly. The world average is 1.5 times weekly.

The study also suggests that Mexican men face additional performance pressure: Nine out of 10 Mexicans preferred “spontaneous” sex — a habit that sets Mexicans apart from people in the United States, Canada and South Korea, where sexual encounters are both less frequent and more often planned.

A primary obstacle to tapping Mexico’s market potential lies in the pervasive taboos around openly discussing male sexual performance and a reluctance to visit a doctor.

Mexicans — 37 percent of men and 38 percent of women — were about as willing as men and women in the U.S. and Canada to talk about sexual health and performance issues with a doctor, according to the study, which surveyed at least 1,000 people each in Austria, Belgium, Canada, Czech Republic, Denmark, Finland, Mexico, Portugal, Romania, South Korea, Switzerland, the United Kingdom and the United States.

Triulzi Garciadiego said Eli Lilly’s marketing efforts are directed at encouraging men to see a doctor. Eli Lilly spends about $3 million annually on a television campaign in Mexico aimed at dispelling the taboos and myths that shadow erectile dysfunction. A 2010 spot featured older men happily seducing their partners, with words at the bottom of the screen saying, “Talk to your doctor. He knows us.” The 2011 spot showed a man deciding “no more excuses” and underscored that 95 percent of erectile dysfunction cases are treatable.

The campaigns — on air since the company launched Cialis in 2003 — have made a difference, said Triulzi Garciadiego.

Cialis has cornered 50 percent of the $200 million erectile dysfunction drug market in Mexico; the drug began outselling Viagra in 2006. (Viagra and Levitra roughly split the rest of the Mexican market.) Cialis sales have been growing 15 percent annually, boosted in 2011 by the debut of the daily pill.

Meanwhile, Pfizer is fighting back. Its chewable Viagra Jet is Cialis’ newest competition. Mexico is Pfizer’s top market for Viagra in the developing world, with about $55 million in sales in 2010.

The chemical patent underpinning Viagra expires in the U.S. this year — which will expose makers of erectile dysfunction drugs to lower priced generics. Hence another good reason to look south.