NEW YORK -- ESPN bowed to public pressure Wednesday and pulled ads for the muscle-building supplement androstenedione, which is used by St. Louis Cardinals slugger Mark McGwire.
The spots for the supplement were part of a new national advertising campaign by MetRx Engineered Nutrition and first appeared Tuesday on ESPN's "American Muscle."
One day later, ESPN backtracked and said it would no longer run the commercial. The next scheduled spot was for Oct. 2.
"Given the debate in the medical and sports community, we decided for now not to run androstenedione ads," ESPN spokesman Mike Soltys said.
The National Collegiate Athletic Association, which had been critical of ESPN on Tuesday, praised the cable network for its decision to pull the ads.
"We have to be careful with our young student athletes and make sure that we providing them with enough sound information to make good judgments," said Cindy Thomas, assistant director of sports scientists for the NCAA.
MetRx defended the ads, saying they have disclaimers saying the pills should not be used by children under 18. The company said it would hold seminars for the media to educate people about the product.
The commercials are still scheduled to run on Fox Sports Net's "Muscle Sport" and fitness shows on Knowledge TV. "Muscle Sport" is a time buy on Fox Sports Net, meaning the network sells the time for the shows, not the commercials.
Debate about androstenedione grew last month after The Associated Press reported that McGwire, who broke Roger Maris' 37-year-old home run record, has used the pills for more than a year. Sales have increased nearly fivefold in that time.
Andro raises levels of the male hormone testosterone, which builds lean muscle mass and promotes recovery after injury. The pill is legal in baseball but banned by the NFL, NCAA and Olympics.
Androstenedione is an adrenal hormone produced naturally in men and women. It is converted in the liver to testosterone, which is used in muscle production.
Though no definitive studies have shown harmful side effects, skeptics say the supplements could have dangerous consequences similar to those of steroids, such as liver damage and heart problems.