A quick web search turns up dozens of sellers offering not only the raw ingredients for making designer drugs, but brazenly advertising the drugs themselves.

Beyond the rapid spread of the new drugs and new drug trends, something else about these designer drugs is new. Terribly new.

In the 1960s and 1970s, people seeking psychedelic experiences usually took LSD, psilocybin (magic mushrooms), or mescaline (peyote). These drugs are potent hallucinogens. For people genetically predisposed to mental illness, or those who take the drugs in an unsafe setting, this is quite dangerous. But these drugs are not directly toxic, even at high doses.

"Things like LSD and mushrooms and mescaline have low toxicity," Nichols says. "The reason is that their target is the serotonin 2a receptor in the brain. They do not interact with receptors that control heart rate or vegetative functions that cause death. Drugs like 2C-E have effects on the serotonin receptors in the brain, but also in the blood vessels and elsewhere. So if you take a truly large dose, which is easy to do, you can have your blood vessels contract, your heart rate go way up, your temperature regulation go out of control. ... There have never been studies on what else they may hit."

LSD and psilocybin have specific effects on serotonin in the brain. But the new drugs are not nearly as specific. In addition to serotonin, they variously affect other vital chemical signals, particularly dopamine and norepinephrine. Because these chemical messengers affect cells throughout the body, they can have drastic, unexpected effects on vital functions such as heart rate and body temperature.

While the new drugs may be more dangerous, even those who value psychedelic experiences warn against the casual use of even the least dangerous psychedelic drugs.

Psychotherapist Neal M. Goldsmith, PhD, author of the book Psychedelic Healing, notes that psychedelic substances have been used for thousands of years by virtually every culture. He sees the "reintegration" of psychedelics into our science and our spirituality as a good thing -- but one "unfortunately fraught with some growing pains."

"With use increasing and prohibitions in place you find young people taking these drugs out of spiritual context, with no real knowledge of their safety or efficacy or dangers," Goldsmith tells WebMD. "It is not surprising people get into trouble. ... Knowledge increases safety ... and there is some danger in going from a state where these psychedelic drugs have been banned, as there is very little knowledge, or experience, or experienced elders to guide appropriate use."