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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Sunday 9th October 2011

I’ve been accused, in the past, of being excessively distrustful of information about poisonous plants given to me by members of the public. I’d have to say I am willing to accept ‘distrustful’ but I wouldn’t say I agree with ‘excessively’. I’m not saying people set out to tell lies but it is my experience that people tend to fill in the gaps rather than admit they’ve forgotten something and it is human nature to personalise stories.

I’ve found that it makes sense to research a story before including it either on this website or in my talks because, quite often, it won’t be precise in every particular. I have made the mistake of finding a story so fascinating that I’ve begun retelling it immediately only to find, later, that it wasn’t as told to any extent.

So, when someone told me they had quit smoking using a Bulgarian product called Tabex made from one of the alkaloids of the laburnum tree I was quite suspicious. On that occasion, however, my suspicion was misplaced and I found that Tabex is a real product though, at the time I looked into it, it was only available in the UK if you were willing to buy it online from a foreign language website.

Laburnum contains the alkaloid cytisine

Laburnum contains the alkaloid cytisine

Now, however, many more people are aware of the existence of Tabex, though it is still not yet available in the UK. This is because the results of a proper randomised, double-blind placebo-controlled trial have been published in the peer-reviewed journal the New England Journal of Medicine.

Researchers from University College London, the UK Centre for Tobacco Control Studies and the Cancer Centre and Institute of Oncology, Poland, took 740 individuals who expressed a desire to stop smoking and split them into two equal groups. Half were given a short course of Tabex while the other half received a placebo. The researchers found that people who had received Tabex were three times more likely to be non-smokers a year after the trial than those who received placebo.

That is a similar result to those seen with other forms of smoking cessation treatment either drug based or using nicotine patches. The clear advantage of Tabex is that it is substantially cheaper than the other therapies available. The NHS Health News website  says that the trial was properly conducted and its results are reliable given the trial size. It says there is a need for much larger trials with different treatment periods to confirm this result and to get more information on the side effects experienced by some of the trial participants.

Just as an aside, I’ve written before about the power of the placebo effect. In the trial, 13.8% of the subjects given cytisine reported side effects including stomach-ache, dry mouth, dyspepsia and nausea but so did 8.1% of those on the placebo. These side effects, for the subjects having Tabex, are to be expected given that cytisine is toxic.

Its apparent success in helping people to quit smoking may well be because it is usually described as having effects similar to but less serious than nicotine. I haven’t been able to access the full paper so I don’t know what it says about possible mechanism but, it seems to me, the similarity between nicotine and cytisine may be at the root of its effect. The cytisine may be replacing the body’s need for nicotine but with a reduced addictive element so that a slowly reducing dose of cytisine frees the smoker from the nicotine addiction.

I have to end with a couple of more pessimistic comments. If cytisine’s main advantage over other replacement therapies is its reduced cost then that saving will be eroded if it has to go through the expense of sufficiently large trials to become fully approved for sale in the EU. And, of course, going from direct from the manufacturer online buying to over the counter from a pharmacy introduces both costs and additional profit margins.

Also, though the cessation rate was three times for Tabex versus placebo the actual figure for people who were non-smoking after twelve months was only 8.4%. So, of the 370 trial subjects, all of whom qualified for the trial by satisfying the researchers that they wanted to quit, just 31 succeeded. Some research has suggested that addiction to nicotine is harder to break than addiction to heroin so the best idea is not to become addicted to either substance in the first place.