Drug scares – how do I know what is true?

We live in a social world – one philosopher once called humanity “the ape that talks”, and we’re constantly talking, discussing, arguing, and sharing ideas and opinions. In general, I think this is great – communication has the capacity to widen our scope, to let us understand each other and the world.

However, like every scientific and technical invention, modern communications (and especially social media and the internet) have their dark side. Beyond the cosy family chat, or judicious and informed news website, There be Dragons. I hope to look at data issues in veterinary practice in a later blog, but today I plan to do battle with just one of those dragons – Rumour. Specifically, the wide range of drug safety rumours that do the rounds on social media.

You’ve almost certainly seen them – Facebook groups and websites that devote themselves to recording all the side effects of a particular medication, or group of medications, and therefore conclude that these drugs are either unethical or dangerous. Perhaps the most active of these sites are those run by “anti-vaxxers”, a relatively new movement, but the drugs that have recently been targeted (mostly by very well-meaning people) include Bravecto and the Lepto 4 vaccine. Some of these claims become seriously hysterical – I have a colleague in practice who became so fed up of people refusing the L4 vaccine because “all the dogs die” that he started pointing out all the dogs in his waiting room who were vaccinated and yet were still very much alive and kicking.

The big problem with these forums is that there are so many pets in the UK (8.5 million dogs alone!) that the vast, vast majority that suffer no effects are invisible, while the tiny percentage that suffer side effects are highlighted, making it hard to determine the actual risk.


Where do these rumours come from?

There are three major reasons, I think, for the current climate of mistrust in medications.

Firstly, the anti-vaxx movement. This was originally an anti-authoritarian political movement primarily in the US, and was to a great extent jump-started by the (now struck off) ex-Dr Andrew Wakefield. Wakefield’s discredited research into links between autism and human vaccines won him first fame, then notoriety (as it emerged that his research data had been faked and that he was in fact being paid to prove the link), and finally his being struck off by the GMC and his articles retracted by the journals that published them. Unfortunately, we still hear people citing his work – even though every follow up study has found no relationship between vaccination and autism.

The second issue is the distrust of big pharma. Here I think doubters are on more solid ground – large companies (the banks especially, in the years following the 2008 financial crisis) have been shown to have acted with callous disregard for their customers, and people can, quite reasonably, be suspicious of their motivations. Years of paying for doctors’ (and, to a lesser extent, vets’) training, offering freebies, and hiding negative results have come home to roost. The problem with the argument, however, is that as taxpayers and citizens, we pay people to keep an eye on medicine safety, so while it is possible to sneak an unsafe drug out onto the market, it won’t stay there for long!

For veterinary medicines, the UK regulator is the Veterinary Medicines Directorate which is an independent agency of DEFRA – i.e. part of the UK government. It is not funded by donations from pharmaceutical companies and operates independently. Their primary role is “To authorise veterinary medicines and to monitor their safety and efficacy following authorisation.” In other words, they test medications for effectiveness and safety before they are allowed to be sold, and then monitor them for problems once they’re on the market.

The other thing to bear in mind is that the drugs companies for veterinary medicines have no motivation to release an obviously dangerous or unsafe product – as vets, we would avoid buying from one caught out doing something that stupid. The veterinary medicine market isn’t big enough for the potential rewards from such a strategy to be worth the risks! Disastrous mistakes do occasionally get made – the permethrin flea-treatment marketed for cats, for instance, where the company believed that the dose was low enough to be safe, and were terribly wrong. It’s worth noting, though, that over-the-counter products (like that one) undergo a much lower level of scrutiny than prescription only products (POM-Vs) do.

So, any harms are likely to be so subtle or so rare that they escape the normal oversight process. I would never argue that this is impossible – but the evidence currently available does not suggest that this is a reason to avoid using effective medications.

The third problem is one that all of us face every day – information overload. Human brains struggle to cope with abstracts like the incidence of adverse effects – it’s not what we really evolved to think about (!). An overload of information means we instinctively recoil and focus on the social element (“the ape that talks” indeed!) – which is why emotive stories along the lines of “my dog died because of drug X!” are much more powerful than the dry statistics quoting the millions of animals that have been safely treated with the drug.


Are you saying that all drugs are safe then?

No, of course not! In fact, I’d go further – all drugs are potentially dangerous. As a pretty good rule of thumb, if a drug has no possible side effects, it isn’t doing anything. The animal body is fantastically complicated, full of incredibly intricate, interlocking machinery; a drug is intended to alter the function of some of those molecular machines. Usually, the side effects aren’t even noticed by the patient, but occasionally they are. That’s why we tend to refer to “adverse reactions” or “adverse events” if harm occurs rather than side effects.

As an example, one of the most commonly used drugs in veterinary medicine is meloxicam – it’s a painkiller and anti-inflammatory, sold under a wide range of brand names. In general, it’s pretty safe as long as it’s used appropriately. However, the side effects may include “loss of appetite, vomiting, diarrhoea, faecal occult blood, lethargy and renal failure… haemorrhagic diarrhoea, haematemesis, gastrointestinal ulceration and elevated liver enzymes.” This is, of course, why these drugs are licensed as POM-V (prescription only medicine, veterinarian) – as vets, we’re trained in safe doses, and patient selection – that same drug at the same dose might well be safe in a young adult dog with a sprained joint, but dangerous in a puppy, a dog in shock, or a bitch in pup.

Interestingly, in human medicine, adverse drug reactions are another major concern, with one study estimating that 6.5% of all hospital admissions are due to drug side effects!

The trick (as every practicing vet has had to learn!) is to balance the risk of using a drug – ANY drug – with the benefit to be gained from it.

Here another odd human cognitive bias comes into play, the salience bias. Basically, we tend to think of exciting and strange events as being more common than they really are – meaning that we are more likely to be concerned about the (rare) side effects than the (common, but often seen) effects of not treating the condition. A good example is the Lepto L4 vaccine. The actual risk of adverse effects is about 0.069% – in that, about 7 in every 10,000 dogs will develop side effects (most of which are very minor). We can compare that to human ibuprofen tablets, where the risk of side effects (most of which are also very minor) is about 10 times greater… so why aren’t we protesting about that? Because we’re familiar with ibuprofen and it’s risks, but the L4 is a relatively new product and therefore we’re more cautious.


So how do I know what’s safe?
Every veterinary medicine has what is called a Summary of Product Characteristics, or SPC (sometimes called the Datasheet). You can access these for free on the VMD’s database and at the National Office for Animal Health (NOAH). The SPC must, by law, include the adverse effects that have been observed at normal doses, expressed as “rare”, “uncommon” etc. This uses a standard framework:

– very rare (less than 1 animal in 10,000 animals, including isolated reports)
– rare (more than 1 but less than 10 animals in 10,000 animals)
– uncommon (more than 1 but less than 10 animals in 1,000 animals )
– common (more than 1 but less than 10 animals in 100 animals)
– very common (more than 1 in 10 animals displaying adverse reaction(s) during the
course of one treatment).

You can, therefore, judge the likely risks.

However, there is a simpler answer – talk to your vet! We aren’t funded by pharmaceuticals, our salaries are paid by you, and most of us aren’t on commission. But we are trained to understand the risks and benefits, and we are ultimately responsible for the wellbeing of the animals that you entrust us with. We have no interest in causing harm to your pets – as professionals our oath is binding on us:

“I PROMISE AND SOLEMNLY DECLARE that I will pursue the work of my profession with integrity and accept my responsibilities to the public, my clients, the profession and the Royal College of Veterinary Surgeons, and that, ABOVE ALL, my constant endeavour will be to ensure the health and welfare of animals committed to my care.”


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