Bad Chemistry II – Poisons

In the second part of this series I’m going to have a look at some specific types of poisons and the treatments that are available for them. This will not by any means be an exhaustive reference source, but more an overview of substances that tend to feature prominently in fiction, and which tend to fit a particular type of purpose within a narrative.

Cyanide (Fast) – The exact definition of a cyanide is a little confusing, but for the purposes of toxicology it tends to be used to describe organic compounds containing the cyanide group (CN). This chemical group is very common in chemistry, but causes problems for many living creatures when released into solution as an ion, something that happens very easy with organic compounds. This ion inhibits the electron transfer chain with, a key reaction in providing energy for your cells.

Cyanide toxicity is fast, and once it’s present within the bloodstream in large quantities it does pretty much fulfill the Hollywood, drop dead in seconds image, this is most likely to happen when it is breathed in as a gas, or absorbed through the skin.

As such, the treatment of cyanide poisoning is heavily complicated by the fact that the victim is quite probably already dead by the time help arrives (as my Toxicology lecturer put it, somewhat flippantly, if a living patient presents with Hydrogen Cyanide poisoning then congratulations they’re going to live). That said in the case of lower doses, or more slowly absorbed oral poisoning, treatments do exist, mostly involving the introduction of substances into the body that the cyanide will react with. This is a not a magic cure all, but will reduce the severity of the poisoning. Prognosis for survivors is fairly good, but long term damage can result, especially to the heart, brain, and the rest of the nervous system.

Metal Toxicity (Slow) – Metal toxicity is often considered together, not because many heavy metals have the same mechanisms of effect, or even because they target the same tissues within the body, but because the body is very poor at excreting them, meaning that they will tend to concentrate within the body over time, a process known as bio-accumulation. Because of this, treatment often involves using substances, known as chelating agents, which will bind to the metal and help it to be eliminated from the body.

This tendency means that such substances have been often been (mis)used, throughout history, to poison a victim over an extended  period of time, often with the intent of avoiding detection or causing the appearance of a chronic illness. It’s important to remember that their tendency to cause slow long term poisoning does not preclude acute toxicity from occurring from a single large dose, but many of these substances tend to produce fairly general damage to organs, which can make for a long and lingering death even in a large exposure. Neurological damage is very common, especially with lead and mercury.

Another key issue with metal toxicity, is the form that they are present in. Elemental metals tend to be poorly absorbed by the body and relatively non-toxic, but when incorporated into organic compounds they can become many times more bio-available, and hence toxic. Elemental iron is sufficiently non-toxic that children’s cereal is pretty much “fortified” by mixing in iron filings, organic iron is highly toxic, which is the reason that the first thing a doctor would establish if your child had overdosed on vitamins, is whether they contain iron or not. Mercury also presents the risk that it will evaporate which makes it much more readily absorbed by the body.

Intentional heavy metal poisoning is now rare, at least in the developed world, primarily because it is very easy to detect, but environmental toxicity is still a very big deal, especially in poorer countries, often linked to us of the substances in industry, or their recovery from used electronics. Toxicity may also result due to illegal or inappropriate incorporation of the metal into another product, often as a dye.

Anticoagulants (Messy) – This usually means the classic rat poison warfarin, although there are a number of similar drugs, and aspirin can produce the same effects. In toxic concentrations these kill via blood loss, primarily resulting from internal bleeding.  Many anticoagulants merely block coagulant production, something that takes an extended period of time and which can be treated by replacing factor precursors and giving a blood transfusion, making it a relatively slow and unpleasant form of poisoning, but one that would be fairly easy to diagnose and treat where medical help is available.

Botulinum Toxin (Potent) – The most potent toxin that I’m aware of is Botulinum toxin which is produced by the bacteria Clostridum Botulinum. This substance causes the food poisoning known as botulism, and is used under the name Botox in a variety of cosmetic medical procedures, as well as some other medical applications. The toxin as released by the bacteria contains a number of very similar substances which prevent the release of neurotransmitters from nerve junctions. Depending on administration route the lethal dose for a human may be less than 0.1 micrograms (or one ten millionth of a gram).

The substance represents an obvious candidate for use in warfare or terrorism. Whilst it is not particularly well suited to use as a weapon in terms of stability or absorption, its incredible potency and relatively straightforward manufacturing process make it a very real threat.

Tetrodotoxin (exotic) – Tetrodotoxin is of interest, primarily because it occurs in a wide range of different creatures, many of which have been used prominently in fiction. Tetrodotoxin is responsible for the toxicity of Japanese pufferfish fugu, the bite of the blue ringed octopus, as well as wide and varied range of toads, sea stars, fish and worms. This is thought to be possible because the toxin is actually manufactured by one of a number of different bacteria, that are living within the creatures.

The toxin acts on the nervous system and serves to paralyze skeletal muscles, usually leading to death as a result of suffocation. The victim can remain perfectly lucid but paralysed until they expire. Whilst its true that the toxin has no antidote, this does not mean that it can not be treated. Treatment primarily consists of supporting the patients breathing mechanically and trying to prevent any further absorption of the drug, although serious cardiac symptoms can also occur as the patient loses the ability to regulate their heart rate. If the patient can be kept alive by supporting respiration for at least 24 hours the effects of the drug will start to wear of, and the patient has an excellent chance of a full recovery.

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