Methodology to measure onset of action

Onset of action has become one of the most topical issues in antidepressant therapy. In general, the speed of onset of action of antidepressants is re garded as too slow. Most patients who benefit from treatment require 2 or m ore weeks of therapy to show signs of response. Since the onset of therapeu tic efficacy is of current interest to physicians and health authorities, t he question arises of how to measure the onset of therapeutic efficacy. The re are many different proposals for the statistical analysis of data to det ermine early onset of action. One of the most important considerations in a nalyzing early onset of action is the definition of criteria. Conventional approaches, such as the De Paula and Omer approach and the Huitfeldt and Mo ntgomery approach, can provide useful information, although they do not tak e into account whether the early response is sustained. The use of pattern analyses does overcome the problem, but the generalizability of their findi ngs is somewhat limited by their use of stringent exclusion criteria. Survi val analyses can provide a more sensitive measure of early changes. Moreove r, this method can easily be adapted to take into account sustained respons e and be used to restrict attention only to those subjects who achieve onse t. In this article, the above-mentioned approaches will be explained with t he help of some clinical examples to achieve a further understanding of the methodology of measuring onset of action.