Shannon-based pharmaceutical firm UCB Manufacturing Ireland recorded pre-tax profits of €573.7m in 2011.
Accounts filed with the Companies Office show that the chief factor behind the company returning to profit was an exceptional gain of €651m after a debt of that amount due to parent company, Belgian-based UCB, was waived.
The figures show that the Irish unit – formerly Schwarz Pharma – increased its turnover by 11pc to €90.2m in the 12 months to the end of December 2011.
In 2011, the numbers employed by the firm were reduced from 126 to 118, with the company's staff costs increasing from €9.6m to €9.8m.
The profit in that year follows a pre-tax loss of €71.9m in 2010.
The profit in 2011 also takes account of non-cash depreciation and amortisation costs totalling €21m.
According to the directors' report, "turnover continued to grow in 2011 with an overall increase of 11pc to over €90m due mainly to continued growth of Neupro in new and existing markets."
Neurpo is used to treat Parkinson's disease and Restless Leg Syndrome.