IBID

Few areas of research have been as fruitful in the identification of new therapeutic products as the serotonin receptor field. At the beginning of 1996, at least 20 drugs with a primary therapeutic action mediated via one of five distinct serotonin receptors and nine drugs interacting specifically with the serotonin transporter were listed as prescription medicines. Between them they accounted for sales of around US$5.6 billion, about 2% of world drug sales for the year 1995 (1). In nearly every case, these drugs were developed using a receptor-targeted approach to mimic, block, or augment the actions of serotonin at specific receptor subtypes. Often, serotonin itself was used as the template for medicinal chemistry. With such an impressive precedent, it is perhaps understandable that serotonin receptors and gene products remain a focus for drug discovery programs. According to published information, at least six distinct receptor targets in addition to those alluded to above are currently the subject of intense research across a broad spectrum of therapeutic categories (see Table 1). Among the most important of these are the 5-HT18 and 5-HT10 receptors, which appear to be key targets for the acute treatment of migraine and associated vascular headaches.