Story Highlights • Authorities say there have been 21 "cheese" deaths in the Dallas area since 2005

• Schools, police have begun campaign to try to stop the drug from spreading

• Middle schoolers cheer after detective says U.S. has the most drug users

• Dad of a teenager who died says: "All it takes is once"

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DALLAS, Texas (CNN) -- A cheap, highly addictive drug known as "cheese heroin" has killed 21 teenagers in the Dallas area over the past two years, and authorities say they are hoping they can stop the fad before it spreads across the nation.

"Cheese heroin" is a blend of so-called black tar Mexican heroin and crushed over-the-counter medications that contain the antihistamine diphenhydramine, found in products such as Tylenol PM, police say. The sedative effects of the heroin and the nighttime sleep aids make for a deadly brew.

"A double whammy -- you're getting two downers at once," says Dallas police detective Monty Moncibais. "If you take the body and you start slowing everything down, everything inside your body, eventually you're going to slow down the heart until it stops and, when it stops, you're dead." (Audio slide show: A father describes his teen son's death)

Steve Robertson, a special agent with the Drug Enforcement Administration in Washington, says authorities are closely monitoring the use of "cheese" in Dallas.

Trying to keep the drug from spreading to other cities, the DEA is working with Dallas officials to raise public awareness about the problem. Authorities also are trying to identify the traffickers, Robertson says.

"We are concerned about any drug trend that is new because we want to stop it," he says.

Why should a parent outside Dallas care about what's happening there?

Robertson says it's simple: The ease of communication via the Internet and cell phones allows a drug trend to spread rapidly across the country.

"A parent in New York should be very concerned about a drug trend in Dallas, a drug trend in Kansas City, a drug trend anywhere throughout the United States," he says.

Middle schoolers acknowledge 'cheese'

"Cheese" is not only dangerous. It's cheap. About $2 for a single hit and as little as $10 per gram. The drug can be snorted with a straw or through a ballpoint pen, authorities say. It causes drowsiness and lethargy, as well as euphoria, excessive thirst and disorientation. That is, if the user survives. (Interactive: What is "cheese"? )

Authorities aren't exactly sure how the drug got its name "cheese." It's most likely because the ground-up, tan substance looks like Parmesan cheese. The other theory is it's shorthand for the Spanish word "chiva," which is street slang for heroin.

By using the name "cheese," drug dealers are marketing the low-grade heroin to a younger crowd -- many of them middle schoolers -- unaware of its potential dangers, authorities say.

"These are street dealers, dope dealers," Moncibais recently warned students at Sam Tasby Middle School. "They give you a lethal dose. What do they care?"

Moncibais then asked how many students knew a "cheese" user. Just about everyone in the auditorium raised a hand. At one point, when he mentioned that the United States has the highest rate of drug users in the world, the middle schoolers cheered. (Watch middle schoolers raise hands, admit they know drug users )

"You know, I know being No. 1 is important, but being the No. 1 dopeheads in the world, I don't know whether [that] bears applause," Moncibais shot back.

Authorities say the number of arrests involving possession of "cheese" in the Dallas area this school year was 146, up from about 90 the year before. School is out for the summer, and authorities fear that the students, with more time on their hands, could turn to the drug.

'Cheese' as common a problem as pot

School officials and police have been holding assemblies, professional lectures, PTA meetings and classroom discussions to get the word out about the drug. A public service announcement made by Dallas students is airing on local TV, and a hotline number has been created for those seeking assistance.

Drug treatment centers in Dallas say teen "cheese" addicts are now as common as those seeking help for a marijuana addiction. "It is the first drug to have even come close in my experience here," says Michelle Hemm, director of Phoenix House in Dallas.

From September 2005 to September 2006, Phoenix House received 69 "cheese" referral calls from parents. Hemm says that in the last eight months alone, that number has nearly doubled to 136. The message from the parents is always, "My kid is using 'cheese,' " she says.

Phoenix House refers them to detoxification units first, but Hemm says at least 62 teens have received additional treatment at her facility since last September.

Fernando Cortez Sr. knows all too well how devastating cheese heroin can be. A reformed drug user who has spent time in prison, Cortez had spoken to his children about the pitfalls of drug use. He thought his 15-year-old son was on the right track.

But on March 31, his boy, Fernando "Nando" Cortez Jr., was found dead after using cheese heroin.

"I should have had a better talk with him," he says. "All it takes is once. You get high once and you die, and that's what happened to my son."

He knows it's too late for his son. Now, he is using his son's story to help others.

"All I can do is try to help people now. Help the kids, help the parents."

CNN.com senior producer Wayne Drash contributed to this report.