Why are so many drugs involved in the treatment of bipolar disorder?

Professor David Taylor: There are several drugs involved in the treatment of bipolar disorder. One of the reasons for this, perhaps the main reason, is that bipolar disorder has 2 opposing poles, hence bipolar – the manic or hypermanic phase, and the depressive phase, and they are qualitatively different, so we need drugs that treat different stages of the illness, the hypermania or the mania, and the depression. We need drugs also that prevent people from going into mania or depression. So, antipsychotics, for example, tend to treat mania, they also are fairly effective at stopping mania recurring in the longer term. Mood stabilisers, which are usually anti-convulsants, like valproate or lithium, are good at preventing people from going into a depressive episode or a manic episode, they are also reasonably effective at treating mania, but probably not effective at all at treating bipolar depression.

Until recently, we thought antidepressants were the ideal medications for bipolar depression, but recently there have been 2 major trials which have shown that they are not effective at all, and also they give rise to a risk of switching to mania, so the use of antidepressants is now falling off and other medications are being used for bipolar depression, particularly quetiapine, which is an antipsychotic but also, by chance, is an antidepressant, and that is now licensed for the treatment of bipolar depression. Now quetiapine is unusual, although perhaps not unique, in that it treats mania, it treats bipolar depression. It also prevents relapse into mania and relapse into depression. So quetiapine ticks all the boxes really. Olanzapine has similar properties, but they’re not so well defined I suspect.