Science Questions

I have a question about anti-diarrhoea tablets. I've never been in favour of over-the-counter remedies but recently accepted a friend's offer of some tablets after a problem an hour before an important event with successful results. How on earth do they work? Anne via email

The answer is that anti-diarrhoea tablets like Imodium contain a version of morphine and they're a morphine-like drug which has some morphine-like effects without all of the morphine effects. It doesn't make you fall asleep or make you feel high for example. One side effect of morphine or morphine-like drugs such as heroin is that it switches off the bowel. In other words it converts motility or movement through the bowel into backwards and forwards mixing motions. That's why people who tend to take a lot of morphine for pain or due to being a drug addict get very very constipated. What scientists have been able to do is to find which bit of the morphine molecule works and makes that effect, made a molecule that mimics that effect and put it in a tablet form.

March 2006