Poison or Coke?

I’m looking at a paper written by some of my colleagues at the NZ National Poison Centre a few years back. This is an important topic for everyone to be aware of: Poisoning following exposure to chemicals stored in mislabelled or unlabelled containers: a recipe for potential disaster, by Yvette C Millard, Robin J Slaughter, Lucy M Shieffelbien, Leo J Schep; New Zealand Medical Journal 26th September 2014, Volume 127 Number 1403.

The problem

Every year people are accidentally poisoned due to hazardous substances being stored in the wrong containers or not being labelled properly. Often the substance is drunk from a bottle that is usually used for drink, such as soft drink, water, sports drink or milk bottles.

Who is at risk?

All age groups are at risk of poisoning in this way, but it is a particularly common way for adults to swallow nasty liquids by mistake. A common scenario is when the driver of a vehicle reaches for a drink bottle and inadvertently picks up a similar bottle containing oil, petrol or even antifreeze. Children are vulnerable because they associate the style of a food container with something they can eat or drink so are unaware of what it really contains.

How serious is this?

The consequences of this type of mistake can be fatal. There have been cases of people drinking paraquat by mistake because it had been kept in a drink bottle and this is almost inevitably fatal. Fortunately, most of the cases covered in by this study were unpleasant but not especially toxic.

Types of chemicals involved

Dishwashing liquid is very commonly stored in the wrong bottles. Petrol, diesel, two-stroke mix are also common culprits. Antifreeze, brake fluids, bleach, mineral turpentine, herbicides, methylated spirits, paint thinners, household cleaners all make the list. None of these are pleasant if you were expecting a refreshing drink of water or Gatorade.

It is illegal to store poisons in food containers

New Zealand food safety regulations explicitly prohibit storing chemicals or “any substance that could cause poisoning” in food containers, whether labelled or not. Yet still people do it. What I noticed in my time at the Poisons Centre is that this practise is surprisingly common in male-dominated workplaces (the list of chemicals involved backs this up). Maybe people think nobody is going to drink from a bottle on the shelf in the workshop anyway, or perhaps there is too much of a, “she’ll be right” attitude?

I do know that it shook all of us who were at work the day a call came through from a young man who had accidentally swallowed a mouthful of what turned out to be paraquat that was stored in a Coke bottle. We all knew his chances of surviving were not good.

ALWAYS KEEP POISONS IN THEIR ORIGINAL CONTAINERS!!

(No apologies for shouting.)

Serotonin and depression

This post is an attempt at summarising and explaining a paper called 5-HT and depression: is the glass half full? Authored by Trevor Sharp and Philip J. Cowen which was published in Current Opinion in Pharmacology, 2011 volume 11 pages 45–51.

The theory that abnormally low levels of the neurotransmitter serotonin (also called 5-hydroxytryptamine, 5-HT) can cause depression is now 50 years old.

The theory arose when it was noticed that depressed patients had low serotonin levels in cerebrospinal fluid, and also that the first effective antidepressant drugs had the effect of increasing the amount of serotonin in the gap between neurons (the synaptic cleft). Since then the old tricyclic antidepressants have been replaced with medications that more accurately target serotonin, the ‘selective serotonin re-uptake inhibitors’ (SSRIs) which have fewer adverse effects and tend to be more effective at relieving depression symptoms.

Despite the progress since 1967, up to half of the patients prescribed antidepressants do not get enough relief from their symptoms, and pharmacologists still don’t clearly understand how changes in serotonin translate to altered mood.

That 5-HT (serotonin) is associated with mood and depression has been shown by pharmacological studies and also positron emission tomography (PET) studies looking at the distribution of 5-HT receptors in the brains of depressed patients. Other studies have shown that artificially restricting dietary intake of the amino L-tryptophan can cause a return of depression symptoms in patients with a history of depression. This is significant because L-tryptophan is the precursor (chemical building block) of 5-HT. Similar L-tryptophan depletion in people who have a high family incidence of depression but themselves have not had depression caused a less severe lowering of mood.

Genetic components

Depression does run in families, with a moderate to high heritability (heritability is a measure of how likely a trait is inherited, low means less likely and high indicates it is more likely to be inherited in a population).

One particular gene, slc6a4, which codes for the 5-HT transporter protein, has been well studied. Levels of the 5-HT transporter can vary by up to sevenfold within the general population. Individuals with low levels of this 5-HT transporter have increased risk of depression when associated with stressful life events. The region of this gene where it is regulated (i.e., ‘the volume control’) is rich in methylation sites which can result in semi-permanent changes to gene expression as a result of environmental influences (such as a stressed or depressed mother during pregnancy, stressful events, childhood trauma).

Neuronal Repair

Current thinking is that increased synaptic 5-HT activates a downstream gene programme that leads to enhanced neuronal plasticity which has failed because of the adverse effects of stress and other environmental and genetic factors.

In effect, some sort of stress derails the ongoing repair and maintenance of brain ‘circuitry’ which can be overcome by bumping up serotonin levels in neurons.

This idea of serotonin enabling improved neuronal plasticity in depressed patients dovetails nicely with ideas of how psychological treatments (such as counselling, CBT, DBT) function to help treat depression. Psychotherapists help a patient to reframe situations and learn more positive ways to view situations. With increased serotonin levels enabling neural repair and realignment of neural pathways, learning is facilitated and so the therapy and drug treatment work together.

serotonin effects