Barbiturates are the single largest category of drugs. There is over 2,500 compounds in this category of which only about 50 derivatives of barbituric acid are marketed for medicinal use, with fewer than 15 in common use today.

Physical effects of barbiturates are similar to alcohol intoxication with a reduction of tension and anxiety. relaxation, slower reaction time, and loss of motor coordination.

In addition, these drugs have a high addiction potential as well as a high dependence potential. If physical dependence occurs, withdrawal symptoms occur if the drug is abruptly stopped. Withdrawals from these drugs produce anxiety, tremors, nightmares, insomnia, vomiting and seizures. Medical detoxification is necessary with dependence on barbiturates since the results are often life-threatening.

A high overdose potential exists with the use of barbiturates. As previously noted in other sections of this manual, all drugs have what is known as an LD ~50, the lethal dose that would kill 50% of the people who took that dosage.

As tolerance develops whenever a drug is taken for a long period of time, drug overdoses would occur more commonly if not for the fact that the LD-50 generally increases with tolerance to the drug. This is not the case with barbiturates. As the tolerance increases and as an individual takes more of the drug for the desired effect, the LD50 remains fairly constant. At some point. the user takes a dosage that exceeds the LD-50 with often fatal results.

This is especially true when the barbiturate is combined with alcohol. This combination is responsible for more overdose deaths than any other drug combination known. Since the early 1970‘s, barbiturates have been steadily replaced by the use of safer benzodiazepines that are less toxic, do not depress the respiratory centers of the brain, and do not produce sleep as often.

There continues to be a large illicit market for the drugs, however, and overdose deaths continue to be quite high.