Pharmaceutical firm Elan was the eighth best performing ADRs (American depositary receipts) in the first half of 2011, returning 98 per cent, according to statistics compiled by BNY Mellon.

Depositary receipts (DRs) are used by foreign investors as a means of investing in international stocks – such as those from Ireland – in their home countries.

ADRs are used by Irish companies to list in the US. The index of eight Irish companies advanced by 10.4 per cent in the first six months of the year, propelled by Elan’s strong performance.