Barbiturates were first used in 1903. They are derivatives of the chemical molecule barbituric acid. There are over 2000 derivatives of barbituric acid that have been used in medicine.

Dependence and abuse liability

It was in 1912 that the first cases of dependence on barbiturates were reported from Germany. Dependence or physical dependence is defined as a condition when long term use of a drug results in the phenomenon of tolerance and discontinuation or dose reduction of the drug leads to onset of negative symptoms called withdrawal symptoms. Tolerance means that increasingly high doses of the drug are needed to achieve the same efficacy.

After initial reports, more followed on the same lines. These reported delirium and withdrawal symptoms on abrupt discontinuation or dose reduction of barbiturates.

It was in 1950 that researchers published a paper that finally established that physical dependence on barbiturates is a possibility that can be induced in the laboratory as well in experimental conditions.

What was surprising was that despite use of barbiturates for over five decades, it was only in the 1950’s that barbiturates were accepted as drugs that could cause dependence.

It took another two decades for the physicians to be aware that these agents could cause dependence and abuse and should be prescribed only sparingly in select cases.

Drug abuse

Drug abuse has been defined by the World Health Organization (WHO, I969) as the “persistent or sporadic excessive use of a drug inconsistent with or unrelated to acceptable medical practice”.

Both dependence and abuse are closely related and are parts of the same spectrum of conditions with abuse being at the lower end of the spectrum and dependence being at the higher end.

Abuse of barbiturates may vary between occasional use of a barbiturate hypnotic at night to intermittent use during the day leading to intoxication.

Severe cases include intravenous use of the agent and finally physical dependence and addiction.

Barbiturate abuse

Regular consumption of 450 mg of a barbiturate that is traditionally used for sedation or sleep induction for a period of eight weeks is likely to lead to a psychological and/or physical dependence. There are around 60 different barbiturate compounds that are in use:-

• The ones that have a short duration of action have a low abuse potential and their use in limited to the hospitals in general anesthesia.
• The ones that have a longer duration of action include phenobarbitone and are used as anti-seizure drugs. Dependence of these agents are also rare but not impossible.
• Barbiturates that are rapidly acting and useful for sleep induction are the ones that lead to a high or a mood change and intoxication. These have the highest abuse potential and may cause dependence. Common agents abused include amylobarbitone, quinalbarbitone, pentobarbitone etc.

Unlike the social profiles of other drug abusers barbiturate abuse is seen among socially stable, middle-aged persons who may be stably employed or housewives. These persons however do not abuse injectable barbiturates.