Hooked on heroin: for a Baltimore teen, one experience with heroin led to a living nightmare. (Close-up: Heroin).

Judy was no stranger to drugs.

By the time she was 15, she smoked pot on a daily basis. She even tried ecstasy at a party or two. The Baltimore teen thought she was tough enough to handle anything that came her way.

But this was like nothing she'd ever experienced. And, suddenly, Judy was scared.

She was pressed into the mosh pit at an Incubus concert. The music was loud and she couldn't hear what her boyfriend said as he passed her a joint. Or, at least, she thought it was a joint. But, after a few puffs, Judy knew something was wrong.

"I felt this warm sensation flood over me, and then I went numb," says Judy, who is now 17 and asked that we not use her last name or picture. "The crowd was pushing me against the stage. I knew that I was getting squashed but I couldn't feel a thing. That's what really freaked me out."

The next morning, her boyfriend told her that he hadn't given her marijuana. It was heroin.

HIGH-RISK HIGH

Judy had always been a little afraid of heroin. She'd seen the hollow, zombielike faces of friends who were strung out on the drug. She even knew a few people who had died from heroin overdoses.

So it shocked Judy to hear herself say, "I want to do it again."

"It wasn't even 24 hours later," she says, "and I was already craving it."

Gail it smack. Or H. Or skag or junk. By any name, heroin is dangerous, addictive, and illegal. About 3 million Americans have used heroin-including nearly 2 percent of 8th-, 10th-, and 12th-graders, according to the National Institute on Drug Abuse (NIDA). "It can be snorted, smoked, or injected," says Dr. Cathrine Sasek, coordinator of NIDA's science education program. "But in all forms, it can lead to an intense addiction, dangerous behavior, and health risks that range from heart infections, liver disease, and breathing problems to lethal overdoses."

Or, as Judy puts it, "When you are on heroin, your whole life is getting high, getting sick, and then doing anything to get more drugs."

FAST TRACK TO ADDICTION

The day after she first smoked heroin, Judy found herself snorting white lines of the drug with her boyfriend. "I never felt anything like it. It just made me all warm and numb and sleepy" she says. "But even that second time, I didn't feel the same rush as the first. And then I started needing more and more of it to get high."

Only a few hours after a heroin high wears off, addicted people, like Judy, often start craving more of the drug. Their bodies turn on them, and they suffer through nausea, vomiting and diarrhea.

"It's like the worst flu you've ever had--and then 10 times worse than that," Judy says. "You think you are going to die. Even when you aren't sick, you're always a little pukey. Your skin feels uncomfortable on you and you're always picking at it. The only thing that makes you feel better is more heroin."

Within just a few weeks, Judy progressed from sampling heroin on the weekends to a daily habit. She dropped out of school and spent all of her time with her boyfriend and his heroin-addicted mother. On the rare occasions when she was home, Judy fought with her family. "My mother tried to get me to admit that I needed help, and I just beat her up' Judy says. "I can't believe I did that. But I was so wild. It wasn't me."

Just nine months after she first tried the drug, Judy was breaking into houses to steal anything she could trade for heroin. "I never turned to prostitution, but I knew I was going down that line," she says.

GETTING A LIFE

Finally, Judy and her boyfriend decided to get clean together. They checked into separate drug treatment facilities. And while Judy has been drug-free for more than two months at the Lois E. Jackson Unit in Cumberland, Md., her real struggles are just beginning. Even talking about heroin during her counseling sessions makes her want to start using again.

Judy knows that she'll always be an addict. But she's mending fences with her family and planning on going back to school to study accounting or interior design. "I want a life. I want a family. I want children;' she says. "I want my parents to be proud of me. And the only way to do all that is to get off this stuff."

RELATED ARTICLE: THREE DEADLY METHODS

Heroin users take the drug in three different ways: They may inject it directly into their veins or muscles with syringes; they may snort lines of it in powdered form; or they may smoke it in rolled, marijuana--like joints.

Most users inject heroin, believing it leads to a more intense high. But smoking and snorting have become popular among young people. That's because many mistakenly believe that heroin is only addicting when it is injected.

"That is a total myth," says Dr. Sasek. "Any way you take heroin is going to hook you. That's just a fact."

The more heroin you take, the more you need. Typically, an addicted individual uses it four times a day. Since the drug may be cut with anything from powdered milk to rat poison, users don't know how much they're really taking. That makes it easy to overdose. Too much of the drug will slow your respiratory system--until you stop breathing and die.

HEROIN AND YOUR BRAIN

Heroin is an opiate, a kind of drug that's culled from the seed of a poppy plant. Other opiates, like morphine, are used as powerful medications to relieve the intense pain of some illnesses, like cancer.

Depending on how the drug is taken, heroin can enter the brain very rapidly, leading to an intense rush. Within minutes--even seconds--heroin travels through the bloodstream to the brain. There, it latches on to opiate receptors located on neurons (see diagram). These cells help the body relieve pain, but can be overstimulated by drugs, such as heroin.

"Heroin floods the receptors," NIDA's Dr. Sasek says. "Eventually, the receptors become used to this overstimulation and need more heroin just to work normally."

If an addicted person stops using the drug, withdrawal symptoms result--such as fevers, sweating, shaking, and chills. This is because of changes that have happened in the brain and body in response to repeated exposure to heroin. Without treatment, the withdrawal symptoms will subside after a week or so. But the cravings can remain for years

Heroin binds to oplatc receptors en neurons (brain cells) in several parts of the brain. This creates a signal for the increased release of dopamine, a brain chemical linked to feelings of pleasure. The action of the drug triggers different responses in different parts of the brain.

THE LIMBIC SYSTEM controls emotions and feelings of pleasure. Heroin acts hero to produce an intense rush, which people addicted to the drug seek compulsively.

THE BRAIN STEM controls basic bodily functions, like heartbeat and breathing. Here, heroin can depress respiratory activity to the point that the user stops breathing and dies.

IN THE SPINAL CORD, herein has an analgesic (pain-relieving) effect. It blocks the transmission of pain messages between neurons, preventing them from reaching the brain.

Added Risk: Deadly Infections

Addiction and overdose aren't the only dangers of heroin. It can also put you at risk of being infected with HIV, the virus that causes AIDS.

HIV is spread through bodily fluids, like blood. Heroin users who share needles can pass the virus to each other. They can also spread other blood--based diseases like hepatitis C and tuberculosis.

Even heroin users who don't inject can become infected with HIV. The overpowering addiction makes them take crazy risks, like having unsafe sex. "When your whole life revolves around getting drugs, you may do anything for them," says Dr. Sasek. "If that means sharing needles or trading sex for drugs, then that's what many will do."