Drug discontinuations in the United Kingdom and the United States, 1964 to 1983: issues of safety.

Since the modern era of drug regulation began in the early 1960s, fewer new drugs have been approved for marketing in the United States than in the United Kingdom. We examined whether information can be obtained about the relative safety of higher and lower introductory rate policies by comparing each country's record of drugs that have been discontinued (removed from the market, withdrawn, or whose licenses were allowed to lapse) while a question of safety existed. We have compiled a list of both older (approved before 1964) and newer (approved in 1964 or later) chemical entities discontinued in the last two decades. With the aforementioned broad criteria to define "discontinuation," and to assess whether a question of safety was involved, our study showed that a total of 24 chemical entities have been discontinued in the United States or the United Kingdom. Nearly half (10 drugs) were products that had been approved in both countries, while the remainder (drugs that had been exclusively available in one country or the other) consisted of four drugs in the United States and 10 in the United Kingdom. Among the drugs introduced during the last two decades, five have been discontinued in the United States and eight in the United Kingdom. Each country's record of discontinuations has been remarkably similar for drugs introduced after 1974: Four have been discontinued in the United States and three in the United Kingdom. Since drugs discontinued while a safety question existed represent only 2% of the new chemical entities introduced, it appears that drugs that reach the market under the prevailing regulatory systems are seldom associated with unacceptable toxicity.