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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Wednesday 28th November 2012

The original planting list for the Alnwick Garden Poison Garden contained some plants where the poisonous nature was rather obscure and some that had been included because of their use as antidotes. Because these plants led some people to be a bit sneery about the garden, there was a re-planting in 2006 with the intention of focussing on well-established poison plants.

There was also a problem with some plants that weren’t suited to the outdoor life in north-east England. One tree that fell into both those problem areas was Citrus aurantium, the orange. It had to be kept indoors for eight months of the year and its justification for being in the garden was the rather weak fact that some people get contact dermatitis from citrus oil.

Now, however, it seems that whilst the species may not have been a good choice the genus was. A paper in the Canadian Medical Association Journal (behind a paywall)1 was widely reported in both the mainstream and the scientific media. Since I haven’t even found a freely available abstract of the paper itself, I’ll rely on the New Scientist to report the story well.2

New Scientist reports that David Bailey of the University of Western Ontario in London, Canada, reviewed the literature and prescribing information of various drugs for any mention of a reaction with grapefruit, Citrus × paradise. Interaction between grapefruit and some prescribed medications has been known for some time but Bailey discovered that the number of such medications has risen 24% since 2008. He found 85 drugs mentioned as interacting with grapefruit and noted 43 of those as capable of causing severe adverse effects.

There is a chemical in the fruit that destroys an enzyme in the body that acts to break down other substances included drugs. Removing the enzyme means the medicine has a greater effect than expected. In the worst examples, one glass of juice could turn a normal dose of medication into an overdose. Though no cases seem to have occurred, it is said that grapefruit and certain cancer drugs could produce fatal consequences.

That thought brings me to homeopathy.

Some months ago, my wife received a questionnaire ahead of a hospital outpatient appointment. In part it asked for details of all medications she was taking whether prescribed or other the counter. It then said ‘Remember to include any inhalers, eye drops, creams, herbal or homeopathic remedies.’

I asked the hospital to explain why it included homeopathic substances when, being completely inert, they couldn’t possibly have a bearing on anyone’s medical condition. That was in August and, last week, I received a reply saying that the Senior Clinical and Development Pharmacist - Pharmacy Department had been consulted and explained that the reference is not intended to imply an endorsement of homeopathic remedies by NHS Borders.

I think I may have touched a nerve because later in the email the sender says ‘I must emphasise again that the use of this description is not in any way intended to suggest that NHS Borders endorses homeopathy as an alternative form of medical treatment’.

I’m assuming the form is intended to guide outpatient doctors when it comes to prescribing something for the condition in front of them. Drug interactions can be very dangerous so it is essential for a doctor to consider what interactions may arise from the medication they are providing to a patient who has not taken it before. I don’t suppose that a doctor has ever decided against providing a proper medicine because the patient is taking sugar pills.

What is not on the form but, it appears, should be, is to ask about the patient’s diet; and not just whether they have grapefruit. I remember being told by a pharmacist that she had been involved in a clinical trial of a new drug and one of the subjects had a response completely unlike any of the others. Only when looking into it did they discover that he drank enormous amounts of coffee and the caffeine had interacted with the trial medication.

Still it is good to know that NHS Borders does not endorse homeopathy. I hope they have said as much to their neighbour, NHS Lothian, currently undertaking an online survey to see if it should fund homeopathy.


1. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? First published November 26, 2012, doi: 10.1503/cmaj.120951 CMAJ November 26, 2012 cmaj.120951
2. Grapefruit makes drugs pack a stronger punch New Scientist Issue 2893 27 November 2012.


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