Truth serum doesn't make anyone tell the truth
Sodium amytal, the barbiturate behind the truth serum legend, cannot force honesty. It loosens inhibitions and slows inventive thinking, so a sedated person may blurt things out. They may also form false memories, which is why courts no longer accept what such interviews produce. The real story of barbiturates is about danger.
Barbiturates are depressant drugs built on barbituric acid. They calm anxiety, bring on sleep and stop seizures, which made drugs such as phenobarbital standard treatments for anxiety and insomnia for many years. They are grouped by how long they act, from ultra-short types like thiopental, lasting about 30 minutes, to intermediate ones lasting three to six hours. Sodium thiopental, sold as Sodium Pentothal, is often confused with sodium amytal, the drug actually used in the so-called truth interviews.
The problem is how narrow the safety margin is. Tolerance can begin after a single dose, and it builds faster for the calming effects than for the drugs' effects on breathing and heart rate, so users chasing the same relief move closer to toxic levels. There is no antidote for an overdose. Combining them with alcohol, opioids or benzodiazepines multiplies the depressant effect: barbiturates make benzodiazepine binding sites respond more strongly, so the combined effect exceeds the sum of the two. The longest-acting types can build up in the body even after the user stops feeling them.
Withdrawal is regarded as one of the most dangerous of any addictive substance, worse than alcohol or benzodiazepine withdrawal, with a risk of fatal seizures. Treatment typically means switching the patient to a long-acting benzodiazepine and tapering it slowly. Older people clear the drugs less efficiently, and the drugs cross the placenta, so newborns can suffer withdrawal and breathing problems.
For these reasons benzodiazepines and the newer Z-drugs have mostly taken over for anxiety and sleep. Barbiturates still have roles in general anaesthesia, epilepsy treatment and some severe headaches, and in high doses they are used in assisted dying, veterinary euthanasia and lethal injection. They also drive up several liver enzymes, which can make drugs such as codeine far more potent. Chemists have also found a use far from medicine, designing artificial receptors that bind barbiturates for molecular devices.
Source: Barbiturate
