Mexico is the largest market for erectile dysfunction in the developing world, with about $200 million in sales every year. 

That is why Pfizer has chosen the country for the introduction of  Viagra Jet, a tablet that can be taken without water and will dissolve quickly -- making it more convenient to use in the heat of the moment. Pfizer hopes that this innovation will help it keep keep its foothold in Mexico’s lucrative erectile dysfunction drug market a year before their patent on the drug runs out and generics enter the picture.

Viagra’s success in Mexico is obvious, but experts in sexual health are not entirely sure why.

Two years after Viagra hit the market in Mexico in1998 and Pfizer launched a multi-million dollar advertising campaign, the number of visits to doctor in Mexico where patients mainly complained about erectile dysfunction increased 279 percent, according to a study.

Erectile dysfunction drugs are a cash cow -- raking in $5 billion worldwide. About 40 percent of the drugs are sold in the US; 13 percent in Latin America; 3 percent in Mexico. Viagra is Pfizer’s sixth-highest selling drug in the U.S. In the developing world, which includes Latin America, it is their fifth-highest selling drug.

And the demand is expected to grow.  According to one report, erectile dysfunction drug sales may increase 150 percent in South America by 2025.

But experts are unclear about the reasons for the drastic growth. 

“[The advertising and sales records] give the impression that everybody is wanting to be very ready and never fail. But to tell you the truth, I have my severe doubts,” said Eusebio Rubio-Aurioles, director of Asociación Mexicana para la Salud Sexual.

The stereotypical image of the hyper masculine, dominant Mexican man may be even less valid today than it was in 1950, when the issue was first discussed in essays about Mexican identity written by Octavio Paz.

The popularity of these drugs suggest it is not because men want to have multiple partners, but because they want to maintain a healthy relationship with their wives.

“Machismo culture is changing,” said Rubio-Aurioles. “Not rapidly, but fast enough to prevent generalizations.”

Researchers are finding that emotionally fulfilling marriages are becoming more important.

The move to emotionally fulfilling marriages is a new trend for the country, one that will be reported in a forthcoming journal of Men and Masculinities. Medical anthropologist Emily Wentzell noticed that shift in her examination of erectile dysfunction and it made her wonder if the market for the drugs is as big as reports indicate.

“I knew erectile dysfunction drugs were big sellers so I expected men to be talking about why they were using them,” Wentzell said. “But we were talking about those not using them.”

In America, erectile dysfunction affects 16 percent of males surveyed in a worldwide report known as The Multinational Men’s Attitude to Life Events and Sexuality Study. In that report, 22 percent who reported erectile dysfunction were from the US, 14 percent from Mexico and 14 percent from Brazil. It was most likely reported by men who were between 70 and 75 years old, and usually accompanied other diseases, such as diabetes (very common among Mexican males), heart conditions and high blood pressure.

Wentzell found that of men well into retirement age (the most likely to self report erectile dysfunction) were the least likely to consume drugs to fix their problem.

These men, who matured when Paz wrote about machismo, were not expected to be faithful, according to Wentzell. Yet in their golden years, they have grown emotionally closer to their wives as their ability to sexually perform decreased.

Younger men were most likely to seek or to expect to seek help for current and future erectile problems, which was surprising given the context. These men said they were actively rebelling against the machismo role their fathers had taken up.

They said they were aiming to be faithful to their wives. As a result, sex is an important component of the relationship and their intimacy.

Even though sexual health experts might doubt the reason -- and the validity -- for the sale of the drugs in the country, they worry about the use of the drug.

Because erectile dysfunction drugs are not funded by insurance companies, they are largely consumed by wealthier clients who pay out of pocket for the drugs and receive private treatment. According to studies, consumption drops off significantly after the first use.

Erectile dysfunction is often a symptom of other medical problems, including diabetes (which is very high among Latinos) and heart disease.

One-time users who aren’t using the drug with doctor’s supervision may be missing the fact that they have health issues that are more pressing than their sexual performance.

“I am concerned, given the fact that the drugs are not controlled as they should be, people go and treat themselves,” Rubio-Aurioles said.

“This leaves a lot of room for undiagnosed conditions that need treatment and has a significant risk for life expectancy.”

Soni Sangha is a freelance writer based in New York City.

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