Don't worry 'bout the 'bute

So today's news (well, what news has managed to slip through the ridiculously large amount of attention Margaret Thatcher's death has been receiving) brings us the revelation that Asda's Smart Price corned beef contains phenylbutazone. I had sort of thought that the FSA's statement after the initial horsemeat scandal might have gone some way to assuage peoples' fear, but it would appear that the media are pretty hysterically reporting about it, and a small sampling of the general public (i.e. my mum) would suggest that people are still worried about it.

"The levels of bute that have previously been found in horse carcasses mean that a person would have to eat 500 - 600 one hundred per cent horsemeat burgers a day to get close to consuming a human's daily dose."-FSA

Let's have a think about phenylbutazone then. It's a member of a group of drugs called the non-steroidal anti-inflammatory drugs (NSAIDs), the same group as ibuprofen and aspirin. This is reassuring- its not some horrifically toxic chemotherapy agent, or poison, or anything like that. It's a painkiller, related to one of the most commonly used OTC painkillers. That's already looking reassuring. It used to be used in humans as a painkiller, but it was discontinued as it was superseded by other NSAIDs which have a better safety profile.

Whoah there, I hear you say in a panicked fashion. It was withdrawn for safety reasons? What safety reasons? ARE WE ALL GOING TO DIE BECAUSE OF CORNED BEEF? Well, in short: no. Yes, phenylbutazone can be associated with some nasty side effects, as can pretty much every drug going, but these are incredibly unlikely with small (I'll come onto how small later), acute doses from the occasional corned beef hash. Aplastic anemia, for example, is associated with long-term therapeutic use of the drug- usually after about a year. Likewise with leukemia, which has an even less clear association with phenylbutazone. I sincerely doubt that there will be many people who eat Asda Smart Price corned beef in large quantities every day for a year, and if there are, I suspect their heart may be more likely to give out than them suffering from any drug toxicity. 

Let's say though that you had eaten some. This doesn't necessarily mean that you will have ingested all of the drug. Drug companies invest quite a bit of money in their drug delivery systems: tablets, capsules, injections etc. There's a reason why corned beef isn't used commonly as a drug delivery system: there's no data on stability of drugs within it or its dissolution properties. For all we know, phenylbutazone may well be broken down if its stored in such a substance for any appreciable length of time. stability. When you take a tablet, you don't absorb all of the drug within it immediately. Some of it wont even get through your GI tract or into your blood stream. Some of it will tag onto blood proteins, whilst some might be converted into inactive metabolites by the liver. Only the free drug portion that remains will actually exert any effect. And in this case, the drug has had to go through all this process already in the horse before it even gets into you. 


All of this is by-the-by when you get down to looking at amounts.  If you eat 1kg of horsemeat containing the highest possible levels of phenylbutazone, the dose you would get in the worst case scenario is 0.0019 milligrams. Back in the days when it was used therapeutically, the dose given was 100mg every 4 hours.

The corned beef in question has been found to contain 1% horse DNA. Lets say that's all horsemeat. And lets say this horsemeat had the highest possible levels of phenylbutazone in it. 

If you ate an entire 340g tin, you'd  a)be fairly greedy or hungry and b) eating 3.4g horsemeat:

3.4g horsemeat= 0.0000019 milligrams phenylbutazone

Now, by my reckoning, that works out as having to eat 100,000,000 tins of Asda Smart Price Corned Beef to get the equivalent of two therapeutic doses (and its only half of the recommended loading dose). Even by Adam Richman's standards, that is a hell of a lot of corned beef. And remember, you'd have to eat that for approximately a year before you got any of the nasty side effects. 

So really, don't worry about the 'bute. The amount of salt in there is more likely to cause toxicity first.

Hxxx