Shares in Sanofi-Aventis, the French pharmaceutical group, fell nearly 6 per cent on unexpected indications that Germany and Luxembourg may authorise the launch of generic equivalents of its blockbuster blood-thinning treatment Plavix in the next few months.

Schweizerhall, a small Swiss-based speciality drugs business, said it expected the German medicines agency to give a positive opinion “shortly” on a version of the drug known generically as clopidogrel, and the decision could be followed by a similar authorisation in Luxembourg during the second quarter of the year.