Question: Why do you use animals to test medicines for children and how do you know they don't taste of anything?

Robert Ives answered on 22 Jun 2020:

Hi,

All potential medicines need to be tested before being given to humans (adults and children) to make sure they are safe and have a good chance of actually working (efficacious). The bodies of children are continually growing and changing through the first years of life and don’t fully mature until around 18 years of age. Because of all the changes happening in children, medicines do not always work in the same way as they do in adults, so sometimes, giving a child a small dose of an adult medicine might not actually work and could actually be very dangerous. Because of this, we also need to test medicines in young animals (called juvenile animal studies) to see whether they respond differently to the adults and we can use this information to help us understand if a medicine is likely to work and be safe in a human child.

We know that many (actually most) young children will not take a medicine if it tastes bad, so we need to be able to make a medicine taste ‘OK’ – not taste wonderful like a sweet, but just ‘OK’. We could carry out taste studies in adult humans (which we also do), but if a medicine does taste bad (and many do) this can result in a medicine needing to be changed (‘reformulated’) which can take a long time (up to a couple of years sometimes) and sometimes even require extra animal studies to check it is safe. Rats like very similar tastes to humans, particularly human children (if you stand outside McDonalds long enough, you will probably see rats scurrying around with bits of burger and fries in their mouths) and we can use them to ‘taste test’ medicines much earlier and make changes to the medicine much faster without using more animals and this can help get a medicine to a child much faster (normally between 6 months and 2 years faster) so can hopefully save more childrens lives.

My trained rats are placed in a special chamber where they can chose to taste a medicine in a small bottle. A computer can count every single time a rat licks the bottle during a very short amount of time (literally a few seconds) and this can tell us how much the rats like the taste. If it tastes horrible, the rats might only lick 1 or 2 times then pull a strange face, if it tastes nice, they might like 50 or 60 times and if it tastes OK, somewhere in the middle (perhaps 20 or 30 licks). By using the number of licks, we can work out how nice (or bad) a medicine is likely to test, then we can add flavours, sugars, etc to see if these make the medicine taste nicer.

Rats are the most accurate way to test the taste of medicine at moment (apart from humans of course), but I also work with scientists in other labs who use amoeba (single celled organisms) and artificial intelligence (machine learning) to predict if a medicine might taste bitter. These are OK at predicting, but not good enough at the moment, but with some more work by some great scientists, they might one day be the best way to test medicines.