Johnson & Johnson, the US pharmaceuticals group, has a month to decide whether to try to claim back full rights over two pivotal medicines as a result of Merck’s $41bn (£29.8bn) planned takeover of Schering-Plough.

Documents filed with the US Securities & Exchange Commission give the timetable and conditions by which Johnson & Johnson could try to cancel its partnership with Schering-Plough for sales of the blockbuster anti-inflammatory drug Remicade and of golimumab, a newer version in development.