Tricyclic antidepressant

Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants, which is important for the management of depression. They are second-line drugs next to SSRIs. TCAs were discovered in the early 1950s and were marketed later in the decade. They are named after their chemical structure, which contains three rings of atoms. Tetracyclic antidepressants (TeCAs), which contain four rings of atoms, are a closely related group of antidepressant compounds. Although TCAs are sometimes prescribed for depressive disorders, they have been largely replaced in clinical use in most parts of the world by newer antidepressants such as selective serotonin reuptake inhibitors (SSRIs), serotonin–norepinephrine reuptake inhibitors (SNRIs) and norepinephrine reuptake inhibitors (NRIs). Adverse effects have been found to be of a similar level between TCAs and SSRIs. Another class of antidepressants, tetracyclic antidepressants, are also used around the world, and they have many similarities to the tricyclic antidepressants. The TCAs were developed amid the "explosive birth" of psychopharmacology in the early 1950s. The story begins with the synthesis of chlorpromazine in December 1950 by Rhône-Poulenc's chief chemist, Paul Charpentier, from synthetic antihistamines developed by Rhône-Poulenc in the 1940s. Its psychiatric effects were first noticed at a hospital in Paris in 1952. The first widely used psychiatric drug, by 1955 it was already generating significant revenue as an antipsychotic. Research chemists quickly began to explore other derivatives of chlorpromazine. The first TCA reported for the treatment of depression was imipramine, a dibenzazepine analogue of chlorpromazine code-named G22355. It was not originally targeted for the treatment of depression. The drug's tendency to induce manic effects was "later described as 'in some patients, quite disastrous'". The paradoxical observation of a sedative inducing mania led to testing with depressed patients.