What are the differences between the two types of antipsychotic drugs and is one better than the other?

Professor David Taylor: There are broadly 2 different sorts of antipsychotic medications. They have different names, which is rather confusing. Generally speaking, they are called typical antipsychotics and atypical antipsychotics. An alternative name is first generation antipsychotic and second generation antipsychotic.

The typical medications have typical side effects, so what we would expect from those is to see movement disorders when you first take them. These are called extrapyramadal side effects, so they include symptoms of Parkinson’s disease like stiffness, rigidity, a peculiar way of walking, and a mask-like face. All these things happen when you first start taking typical medications.

Atypical medications are not typical, they are atypical, in as much as they don’t typically cause these movement disorders. So if you are given a typical drug you can expect to get these movement disorders. If you are given an atypical drug, you can more or less expect not to get them.

There are some other differences too. So, for example typical drugs also cause a rise in the level of prolactin, a hormone in the body, soon after starting taking the medication. Atypical drugs, most of them do not cause this rise in prolactin. And prolactin has a number of different effects, so if you have a high prolactin level on typical drugs you might find you have a lower interest in sexual activities for example, you have a lowered libido, you may have difficulty having sex. If you are a woman, you may notice that your periods stop. Men and women both may show signs of breast tissue growth and even, in some cases, milk production. So prolactin has profound effects on the body, and typical medications typically produce high levels of prolactin. Atypical drugs with one or two exceptions, tend not to do that.

With the atypical/typical delineation, some typical drugs don’t cause as many movement disorders as some of the other typical drugs, so they are slightly atypical. With atypical drugs, some drugs cause a little bit of movement disorder, some of them cause a rise in prolactin, so Amisulpride and Risperidone for example cause a rise in prolactin.

If newer drugs have less side effects, why isn’t everyone given them?

We need to be clear about terms really, because when you talk about less or fewer side effects, that isn’t very helpful. What we need to talk about is tolerability, or perhaps better still acceptability. If we talk about the number of side effects, then one drug might cause one side effect, which is instant death, and another might cause two, which is, I don’t know, a runny nose and a stiff arm, and I know which one of those two drugs I’d rather take, and it’s the drug with the most side effects. So fewer, or more side effects doesn’t really tell you very much about the medication. Whether a drug is acceptable to the people who are taking it is a much better way of looking at things.

Generally speaking atypical drugs are more acceptable to patients than are typical drugs and that’s because with atypical drugs, you tend not to see these acute movement disorders, you tend not see increases in prolactin, and you also tend to see much less of the long term movement disorders, something called tardive dyskinesia, which involves abnormal movements round the face, and the mouth, and the tongue, which develop over time with typical drugs in about 5 per cent of people per year, but with atypical drugs, the rate is much lower, perhaps as low as 1 per cent of people per year.

Most people are given atypical drugs, perhaps three quarters of people in the UK, for example, are given atypical drugs. Those people who are on typical drugs are generally speaking those people who have been on them a long time, find them acceptable and effective, and they are usually watched closely for signs of tardive dyskinesia.