• Question: if a person takes some medicines, why does it have some nasty side affects if it helps you

    Asked by nikzliverpool to Lyn, Katy, Paul, PB, Ruth on 25 Jun 2013.
    • Photo: Paul Waines

      Paul Waines answered on 25 Jun 2013:

      @nikzliverpool- Unfortunately, we sometimes get some nasty side effects because the medicine we are taking might also be slightly poisonous to us, as well as the disease we are treating. The best example I can think of is when chemotherapy is used to treat cancer. This is why it can lead to hair loss and make people feel incredibly ill. We may also be slightly allergic to certain medicines- for example, I am unable to take certain antibiotics for this reason.

      These side effects vary from person to person, and from medicine to medicine, and it is important to be aware of them before you take any medicine- if the side effects are too severe, then you may have to try something else.

    • Photo: Katy Brown

      Katy Brown answered on 25 Jun 2013:

      Sometimes medicines will help one thing but cause other symptoms, and if that’s the best medicine we have you need to weigh up if your life is better with or without the medicine. Also, some people react differently to different medicines so it’s worth trying a few to find one which works well with your body.

    • Photo: Ee Lyn Lim

      Ee Lyn Lim answered on 25 Jun 2013:

      Hi Nikhil! I think most of the time this happens because we don’t fully understand what the drug DOES. When we first started inventing medicines, it was more of a ‘eat this and see what happens’ method – if it worked, we’d use it as a treatment, but we wouldn’t really know how or why it did what it did! So when it also affects other parts of your body, we’re surprised – but we really shouldn’t be!

      Of course, scientists are working hard all the time to understand exactly what our medicines do. Sometimes when we find this out, we can change the way we make the medicine to make sure it only does what it’s supposed to do. But a lot of the time, even though we know the medicine can harm people, we still have to use it to treat people because we have no other way to make them better.

      Like Paul mentioned, chemotherapy is a good example – a lot of the drugs we use kill cancer cells because they’re toxic to fast-growing cells, but that means they’re harmful to some of our healthy cells too! Hair follicle cells and blood cells also grow really fast, so they’re the first ones to go – that’s why cancer patients often lose their hair, and become really weak against infections. Many scientists around the world (I’m one of them!) are doing research to come up with drugs that kill cancer cells in other ways, so they leave healthy cells alone, but in the meantime, because we have no other way to treat cancer, we have to keep using those drugs.

      It’s not just in cancer either, this applies to all kinds of meds that we use to treat disease. The more we know about how the drug works, the more specific it is, and the less likely it is to have side effects. Of course, sometimes people’s bodies react differently to medicines, so there will always be side effects (like allergies) that we don’t expect.

    • Photo: Peter Balfe

      Peter Balfe answered on 25 Jun 2013:

      I can’t remember where this quote comes from :
      “show me a medicine without side effects and I’ll show you a medicine that doesn’t work”.
      Why is this statement made? Any chemical which targets a living thing binds to something, a chemical, a structure, a sequence of DNA.
      Unfortunately we are all mode of the same chemicals and structures, so we hit the problem of specificity. Targeting something, such as a disease organism, has the invitable risk of “off target effects”. Collateral damage if you like.
      The best medicines have high specificities. We formalise this with a ratio we call the “therapeutic index”, essentially we compare the amount of drug needed to kill the target with the amount needed to kill your cells. The bigger the difference the better. For example if the amount need to kill the target was 10, whereas you needed 10,000 to kill your cells, you’d have an index of 1,000 and a great drug.
      Many drugs however, especially some of the older more toxic cancer therapies have an index of only 10 – 20. Meaning that although they often do work, their dosing is critical and their side effects can be dreadful. Understanding the therapeutic index, and finding ways to drive it up, is a major part of pharmaceutical development.

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