No antidotes for most drugs

science Tuesday, March 30, 2010. Post by David Bradley

A shocking thought about drugs of abuse

Dr. Shock MD PhD, aka Walter van den Broek, posted a pocket size psychiatric examination and diagnoses booklet, a small PDF file with “everything necessary to become an efficient psychiatrist.” I was quite fascinated to read these crib sheets for psych testing and diagnosis, explaining the basics and acting as a reminder for clinicians carrying out a mental status examination, differentiating between delirium, dementia, and depression and emergency room psych.

It was when I got to the chemistry section – the drugs – that I was most intrigued. Some of them have antidotes that vary in their success in saving lives, but require the victim to recognize an overdose (which is usually not possible) and for medical help to be close at hand. There are hospital antidotes for acetaminophen (paracetamol in the UK), cocaine, and benzodiazepines, and opiates (heroin and its chemical cousins), but the lethal dose varies considerably and no single antidote is 100% effective even if prescribed quickly and at precisely the right level.

The vast majority of substances of abuse have no antidote:

Alcohol – Potential lethal dose: 350–700 mg (serum)

Amphetamines – potential lethal dose: 20–25 mg/kg

Barbiturates: Short-acting (Potential lethal dose: >3 g); Long-acting (lethal dose: >6 g)

Non-benzo hypnotics – lethal dose varies with tolerance

Hydrocarbons (lighter fuel, aerosols, glue etc) can kill instantly

Phencyclidine/ketamine cause many problems and have no antidote

Salicylates – Potential lethal dose: 500 mg/kg

Tricyclics – Potential lethal dose: 35 mg/kg

Nicotine – Mortality rates in the medium term are high

There are countless other drugs on the blackmarket and available under the counter that are potentially lethal and simply have no antidote. Among them the so-called “legal high” mephedrone that is in the UK news following alleged fatal overdose cases and calls for it to be banned.

“The trouble is that most patients are used to some of the drugs and underestimate the risks,” explains van den Broek. “Most intoxications are complicated with the combination of other drugs or alcohol, also poor physical condition is also a factor that makes outcome unpredictable.”

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