Toxicology Thursday: Opiates

Opium refers to the crude extract obtained from poppy plants. Opium itself is fairly easy to obtain directly from poppies but its effects on the body are rather mild in contrast to other modified forms of opium. Opium has been modified into several, more potent drugs known as opiates; most notably, these are morphine, codeine, and heroin.

Morphine was the first developed opiate; it is named after Morpheus (the Greek god of dreams) for it’s ability to put the user to sleep or even in a coma.

Codeine is the second most abundant alkaloid found in opium. To work in the body, enzymes must first convert codeine into morphine- codeine therefore is slower-acting and much less addictive.

Heroin (also known as diamorphine) is a modified form of morphine with two acetyl groups. The acetyl groups increase the compound’s solubility in fats meaning it can pass through the blood-brain barrier very easily, allowing it to interact directly with the opioid receptors in the brain- making it far more potent and addictive.

The greatest medical benefit  of opiates is that they provide pain-relief. However, there is a darker side to the relaxed state such drugs can put you in; in the case of an overdose, the sedation deepens rapidly into a coma and the respiration rate drops substantially since opiates reduce the sensitivity of the respirator centre. Eventually, the respiratory failure leads to death.

Toxicology Thursday: Digitalis

Digitalis is a very effective poison given that it is readily available and lethal in very small quantities. But before you start plotting the demise of your enemies, it is worth noting that digitalis is also detectable in very small quantities.

Digitalis refers to compounds extracted from foxgloves which have specific and dramatic effects on the heart . Digitoxin is one such compound ; it has a serious effect on the heart because of its ability to dampen the electrical signals that coordinate the contractions of the cardiac muscles. In low doses, this causes arrhythmia (an irregular heart beat). However, in higher doses, digitoxin can completely block electrical signalling – effectively paralysing the heart.

Interestingly enough, atropine (a different toxin) can be given to stimulate the heart and work as an antidote to digitoxin poisoning or overdose.

Toxicology Thursday: Eserine

The Calabar bean is a natural sources of poison with a rich cultural history.

In Nigeria, in the early 19th century, there was a practice of feeding a paste of these poisonous beans to people accused of witchcraft, murder, or rape. If the person on trial died from poisoning, they were guilty and, if they survived, they were innocent.

Contrary to popular belief, there may be more logic behind this judicial system than initially meets the eye; guilty defendants would be more cautious or fearful about being exposed and so might be inclined to swallow the paste more slowly than an innocent. A slow administration of the poison allows for a longer exposure time increasing the absorption of the poison and, hence, worsening its effects. If this notion was true in every case, in general, innocent defendants would become quite ill but guilty defendants would most likely die.

The active agent of Calabar beans is physostigimine (also known as eserine); this toxin also disrupts the parasympathetic nervous system but in a different manner to atropine.

Acetylcholine (an important neurotransmitter) must be broken down after it performs its task- otherwise, the neurotransmitter would keep activating receptors and produce unwanted effects in the body. Eserine inhibits the enzyme that breaks down acetylcholine – producing opposite (yet equally extreme) effects to atropine poisoning. Whilst atropine dilates the pupils, eserine constricts them. Similarly, whilst atropine causes heart palpitations ands a rapid pulse, eserine poisoning results in heart paralysis.