Drug abuse and dependence

• Opiates and narcotics are powerful painkillers with sedative and euphoric qualities. These include heroin , opium, codeine, meperidine (Demerol), hydromorphone (Dilaudid), Oxycontin and others.
• Central nervous system stimulants include amphetamines, cocaine , dextroamphetamine, methamphetamine, and methylphenidate (Ritalin). The most commonly used stimulants are caffeine and nicotine. These drugs have a stimulating effect and can produce tolerance.
• Central nervous system depressants include barbiturates (amobarbital, pentobarbital, secobarbital), benzodiazepine (Valium, Ativan, Xanax), chloral hydrate, and paraldehyde. The most commonly used, by far, is alcohol. These substances produce a soothing sedative and anxiety-reducing effect and can lead to dependence.
• Hallucinogens include LSD , mescaline, psilocybin ("mushrooms"), and phencyclidine (PCP or "Angel Dust"). They have hallucinogenic properties and can produce psychological dependence.
• Tetrahydrocannabinol (THC) is the active ingredient found in cannabis, marijuana , and hashish. Although used for their relaxing properties, THC-derived drugs can also lead to paranoia and anxiety.

Drug intoxication and drug overdose may be accidental or intentional. Drug withdrawal symptoms can occur when use of a substance is stopped or reduced. Withdrawal symptoms vary, depending on the abused substance. The onset of withdrawal symptoms depends on the length of time the drug normally stays within the body. Drug intoxication, overdose, and withdrawal can be life-threatening in some situations.