Is it the concentration, rather than the drug itself, that has side effects?

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Paul Anderson

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Paul Anderson  asked the Naked Scientists:
Hi Chris and team,

Scientists isolate some chemical which does x and it is held up as the new discovery and is put into a pill, but I often wonder how many times this concentration into a pill has then had side effects because of its concentration, that might not have happened if it had been consumed in its raw state in a plant where other chemicals might have had a moderating effect. Now I suppose you will say that this is why pharmaceutical companies spend so much on R and D and why it is not rushed onto the market. Okay, I will phrase my query a different way. How many times have they got it wrong and what are some examples? I cannot remember all the background to thalidomide but that certainly had repercussions.

What do you think?


Offline DoctorBeaver

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That is undoubtedly true in some cases. I have just been on a course of painkillers and taking 1 at a time was fine. If I took 2, however, I would start to feel nauseous.

Think about it, the ultimate side-effect of just about any drug is death through overdosing!
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Offline Chemistry4me

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Risk evaluation is carried out by exposing test animals (usually rats) to a chemical and then monitoring them for signs of harm. To limit the expensee and time needed, the amounts administered are hundreds or thousands of times greater than those a person might normally encounter. But then again, if a substance is harmful or not harmful to animals, is it necessarily harmful/not-harmful to humans?
Many foods contain natural ingredients that are far more toxic than synthetic food additives or pesticide residues, but the ingredients are ignored because the foods are familiar. Peanut butter, for example, may contain tiny amount of aflatoxin, a far more potent cancer threat than sodium cyclamate, an artificial sweetner that has been banned in the US because of its 'risk'
All decisions involve tradeoffs. Do the beneficial effects of  a new drug outweigh a potentially dangerous side effect in a small number of users? The answers are not always obvious...
« Last Edit: 21/01/2009 00:15:56 by Chemistry4me »


Offline lancenti

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It contains a list of drugs that were withdrawn in the United States in 2005. That should give you a pretty extensive list of drugs withdrawn, why it was approved and why it was pulled out of the market.

As DoctorBeaver has stated, OD will generally kill someone but concentration is not always the reason why a drug will kill someone. While there will always be a minimum concentration since our body is very capable of eliminating foreign chemicals, it can't do it fast enough some times or actually activates the drug's toxic properties. For example, ethylene glycol is only toxic after it is metabolized in the body. I suspect that if we remove the enzymes responsible for metabolizing ethylene glycol into oxalic acid, it would be a pretty nifty sweetener. However, if we didn't have the enzymes to metabolize ethylene glycol, we'd also not be able to enjoy alcohol.