27 February 2012
ByAppeared in BioNews 646
The Magic of Medicine
Organised by the Dana Centre
Dana Centre, Science Museum, 165 Queen's Gate, South Kensington, London SW7 5HD, UK
Thursday 16 February 2012
Is medicine magic? No, of course not. The active ingredients in the medicines we take are simply chemical compounds which interact with our bodies to produce an effect. And yet, when we take a pill and our headache promptly disappears, it can all feel a bit miraculous to someone who doesn't know the chemical mechanisms.
The study of how any substance affects our body comes under the scope of pharmacology, and the Science Museum's Dana Centre ran a fascinating talk on advances in this field throughout history. It also touched on where pharmacology might be heading. It seems that there is still plenty to be learnt from naturally occurring compounds, while advances in genetics may pave the way for better-targeted treatment, and usher in an era of personalised medicine.
Ancient civilisations were no strangers to drugs. The Greeks used to chew willow bark for pain relief (the active compound in willow bark is the main ingredient of aspirin). The Incas chewed coca leaves, which contain a trace of the active ingredient in cocaine, for strength and energy.
Indeed, modern day 'drugs of abuse' are actually concentrated forms of some of the oldest remedies in existence, Dr Chris John, senior lecturer of pharmacology at Imperial College, London, UK, pointed out. Opiates, for example, were taken for a host of ailments, from deafness to melancholy to venomous bites. According to an ancient Egyptian papyrus from 1550BC, opium mixed with fly excrement and administered for four days would prevent children from crying (I suspect that it would still do this today, but can understand why this concoction has never made it into clinical trials). As recently as the 19th century, Queen Victoria was prescribed cannabis for menstrual cramps.
Indeed, derivatives of cannabis are used in modern medicine. Other than affecting mood, cannabis also stimulates the appetite. Pharmacologists used the structure of the active compound in cannabis to create the drug dronabinol, which can boost appetite in HIV (human immunodeficiency virus) patients. Another drug, rimonabant, is prescribed as an anti-obesity pill because it reverses this effect, Dr John explained.
But 'magic bullets' do not exist and all medicines have undesired side effects. Rimonabant, for example, can produce the opposite effect of cannabis on mood and make people feel anxious and depressed.
Conversely, toxic substances can also be useful as medicines, explained Dr Steve Trim, director of the company Venomtech. His team investigates novel uses for snake, tarantula and scorpion venoms.
He described a type of rattlesnake whose venom relaxes the blood vessels. It causes blood pressure to plummet, killing nearly one in a hundred of those unlucky enough to be bitten. Sir John Vane, who went on to win the Nobel Prize for his work on aspirin, revealed the chemical mechanism at work here and inspired a hunt for a drug to lower blood pressure in a more controlled manner to treat hypertension. This search culminated in the production of captopril in the mid-seventies. Captopril is still used to treat high blood pressure today.
Drugs can also act differently depending on who you are, Professor Glenda Gillies of Imperial College in London, explained. For example, the hormone oestrogen can be used as a drug for Parkinson's disease in women. In men, however, it makes the disease worse.One major challenge for pharmacologists is to understand the likely outcome of someone taking a drug. Professor Julia Buckingham, also from Imperial College, said that two scientific disciplines are becoming increasingly important in this regard: molecular biology and genetics.
When discussion turned to the field of personalised medicine, the speakers touched only tentatively on the heated ethical debates around selective medicine prescriptions. An argument against the overuse of genetic screening was offered by Professor Donald Singer, clinical pharmacologist at the University of Warwick.
He questioned what would happen if a patient was marginally less likely to benefit from a drug, based on their genes. Would we treat them? Would we hope that the drug helped a little? Would we be less likely to offer the drug, if it was expensive? On the other hand, he pointed out that there is no point in wasting years on having a treatment with negative side-effects and no discernible benefit, if we could avoid it. There is clearly a lot more to be discussed here, and although members of the audience did raise some questions, they were generally reluctant to probe any further.
In any case, the evening had more of an educational emphasis for me and I learnt a lot. The overall message was that many chemical compounds have vast potential as medicines and that when used as such, their effects can be extraordinarily complex. That is precisely where the magic of medicine lies.