Hallucinogenic drugs are substances that distort the perception of objective reality. The most well-known hallucinogens include phencyclidine, otherwise known as PCP, angel dust, or loveboat; lysergic acid diethylamide, commonly known as LSD or acid; mescaline and peyote; and psilocybin, or "magic" mushrooms.

Under the influence of hallucinogens, the senses of direction, distance, and time become disoriented. These drugs can produce unpredictable, erratic, and violent behavior in users that sometimes leads to serious injuries and death. The effect of hallucinogens can last for 12 hours.

LSD produces tolerance, so that users who take the drug repeatedly must take higher and higher doses in order to achieve the same state of intoxication. This is extremely dangerous, given the unpredictability of the drug, and can result in increased risk of convulsions, coma, heart and lung failure, and even death.

Physical risks associated with using hallucinogens:

• increased heart rate and blood pressure
• sleeplessness and tremors
• lack of muscular coordination
• sparse, mangled, and incoherent speech
• decreased awareness of touch and pain that can result in self-inflicted injuries
• convulsions
• coma; heart and lung failure

Psychological risks associated with using hallucinogens:

• a sense of distance and estrangement
• depression, anxiety, and paranoia
• violent behavior
• confusion, suspicion, and loss of control
• flashbacks
• behavior similar to schizophrenic psychosis
• catatonic syndrome whereby the user becomes mute, lethargic, disoriented, and makes meaningless repetitive movements

Everyone reacts differently to hallucinogens--there's no way to predict if you can avoid a "bad trip."