Evidence-based prescribing of antidepressants

Modern antidepressants are required to undergo extensive clinical investigation before their commercialisation is authorised, and this provides the basis for the "evidence-based recommendations" for their use. Because of the rigorous methodology required in formal clinical trials in order to establish efficacy, the population studied and the conditions of use of a treatment are likely to differ substantially from those encountered in everyday clinical practice. There is limited opportunity in clinical trials for casual observation of the effects of the drug, its efficacy in patients with co-morbid disorders, or its use outside of the strict indication for which the compound seeks a licence. The observations, case studies, open trials and small comparative trials that are conducted on an antidepressant after it has been launched can provide important information. The less rigorous methodology is to some extent compensated by their relevance to everyday prescribing and their openness to chance discoveries. They can provide complementary information on responder characteristics and acceptance of side effects and can suggest potential conditions and indications not originally foreseen. This body of data can be referred to as "prescribing-based evidence". The obvious complementarity of these two bodies of information is illustrated by reference to the serotonin and noradrenaline reuptake inhibitor (SNRI), milnacipran, which has been the subject of intense post-marketing study, especially in Japan. The newly discovered efficacy of milnacipran in chronic pain, both associated with depression and in conditions such as fibromyalgia, is an example of the extended understanding that can be obtained by such studies.