Scientometric assessment of drugs for chronic pain, 1979–2013: rapid growth of publications, paucity of successful drugs

The aim of this study was to find signs of progress in the pharmacotherapy of chronic pain over the past 35 years using scientometric analysis. The following scientometric indices were used: 1) popularity index, representing the share of articles on a specific drug(s) relative to all articles in the field of chronic pain; 2) index of change, representing the degree of growth in publications on a topic from one period to the next; 3) index of expectations, representing the ratio of the number of articles on a topic in the top 20 journals relative to the number of articles in all (>5,000) biomedical journals covered by PubMed; and 4) index of ultimate success, representing a publication outcome when a new drug takes the place of a common drug previously used for the same purpose. Publications on 55 drugs used in the treatment of chronic pain were assessed during seven 5-year periods, from 1979 to 2013. The rate of rise in the number of publications on chronic pain was exponential, with an increase of nearly ninefold from 2,346 articles over the 5-year period 1979-1983 to 21,095 articles in 2009-2013. However, despite this huge increase in publications, our scientometric analysis did not reveal signs of really successful drugs in this field. For the 2009-2013 period, the popularity index had a meaningful magnitude (from 0.5-2.8) for only 13 of 55 drugs. Five of them were opioids, including morphine, which had the highest index value of all drugs (2.8). None of the drugs had a high index of expectations in 2009-2013. The index of ultimate success was positive only with triptans in the relatively limited area of acute treatment of migraine. As a result, despite rapid growth in the number of publications, our scientometric analysis did not reveal signs of substantial progress in the field of pharmacotherapy for chronic pain.