How do doctors decide which antipsychotic drug to prescribe in the first instance?  

Professor David Taylor: Prescribers, I suppose, have their own favourites, favourite medications with which they’ve considerable experience and confidence, so many prescribers will feel very confident in using medicines like olanzapine or risperidone, atypical drugs which have been with us for longer than 10 years, which are reliably effective and reliably acceptable. There are other medications too which might be chosen in certain instances. Generally speaking, the choice of drug is based on different side effect profiles, so for example, some of the medicines cause weight gain, so if you have somebody who is already overweight, you might chose a medicine that is less likely to give rise to weight gain than one that actually does cause weight gain.

The discussion about side effects is the most important bit really, because people vary in what they will accept as side effects. One person might think that constipation is a terrible side effect to have, another might think that being made drowsy is an unacceptable side effect. So each person will have a different view of the side effects, both in the abstract, ie looking at them on a piece of paper and thinking about what they might be like, and also in reality, when they actually experience the side effect that they have been told might happen, they may predict that it will be acceptable to them, but find that it’s actually inacceptable.

A kind of continuing dialogue between the prescriber and the patient about medication is what should be aimed for.

You can look at the incidence or prevalence of side effects in a population of patients in a trial and you might find that, for example, 20 per cent of them put on weight but you don’t know when you are prescribing for a particular person whether they are in that 20 per cent who put on weight or in the 80 per cent that don’t. So in almost all cases you have to take the medication to find out what side effects you are going to get.