Alcohol is the oldest drug known to man, and also the most widely-used drug. So, I would imagine it is the most widely-abused drug, as well.
Marijuana.
By a substantial margin, alcohol is the most widely abused drug in every age group—including children. However, marijuana is the most widely used illicit substance among all age groups, but “club” drug use is increasing.
Alcohol is the most widely abused depressant.
Crack cocaine and nicotine, in that order.
Stimulants, in the form of caffeine (coffee and tea). These drugs can produce the desired wakefulness, alertness and sense of well-being, but can also produce cardiac arrhythmias, tremors, insomnia, as well as withdrawal symptoms for some people. The second most widely abused group of drugs are the nicotine containing substances - cigarettes, cigars, and chewing tobacco. The most widely used illegal drug is marijuana (except where it can be obtained legally, for medical purposes, in nearly a third of the states of the United States).
It contains caffeine which is a stimulant, and it is most widely available and abused drug.
Alcohol Marijuana is the most abused illicit drug in the United states army
tramadol, codeine (Tylenol 1, Tylenol 2, Tylenol 3), hydrocodone (vicodin), dihydrocodeine (dhc), oxycodone (percocet, oxycontin, etc), morphine, hydromorphone (dilaudid), oxymorphone (opana), meperidine (demerol), fentanyl (actiq, etc), buprenorphine (suboxone/subutex), methadone, and in some countries diacetylmorphine (heroin/diamorphine -- for cancer pain)opium tinctures are still, very rarely, prescribed in the united states. immodium is also technically an opioid. kratom isn't prescribed, but has opioid effects, as does myrrh to some extent.There may be others, but I don't remember them at the moment. There are also analogues of the above substances.
Alcohol
Alcohol.
alcohol