Sir

Your timely News Feature “The safety catch” (Nature 434, 554–556; 2005) points out the need for better post-marketing safety surveillance of new drugs by the US Food and Drug Administration. At present, after a drug is approved on the basis of trial results, its effects in widespread use are difficult to assess and authorities have little power to control its promotion. Let us consider the consequences of a two-stage approval process for new drugs.

During the period of a few years between initial and final approval, the drug would not be promoted to doctors or (as is legal in the United States) to patients; it would be used only by patients whose conditions had not responded to existing drugs. In return, the clock would be stopped on patent expiration, which would compensate the manufacturer for the delay in promoting the drug more widely.

The public would benefit from the gathering of necessary safety data; the risk would be taken by a limited number of patients, in return for the chance of a more helpful medicine. Both manufacturer and public would benefit from the saved cost of not promoting new drugs that fail the post-marketing safety surveillance.

Incidentally, a similar but more prolonged postponing of patent expiration on new antibiotics would help to delay bacterial resistance to them, because they would not be used initially unless the previously available agents were ineffective. This would also make the economics of limited use of new antibiotics much more fair to the manufacturers.