ZURICH (Reuters) - Prosecutors in Tokyo raided offices of Swiss drugmaker Novartis <NOVN.VX> on Wednesday as part of an investigation into alleged use of manipulated data to promote its best-selling blood pressure drug Diovan.
Japan's health ministry filed a criminal complaint against Novartis's local unit in January, saying it may have violated the law when it cited studies based on allegedly manipulated data in advertising.
Novartis said at the time that it had implemented corrective measures.
In a brief statement on Wednesday, it confirmed the Tokyo prosecutor's office was conducting an on-site investigation at its offices in the country and said it would cooperate fully.
Anyone found guilty of exaggerated advertising of drugs in Japan can be punished with up to two years in prison or a fine of as much as two million yen ($19,100), or both.
Several Japanese hospitals have stopped offering Diovan after two universities retracted papers printed in foreign medical journals on the drug's effectiveness in preventing strokes and heart disease.
Japan is an important market for Novartis, accounting for around a quarter of Diovan's global sales before the scandal. Annual sales of Diovan in Japan have topped 100 billion yen ($954 million) since 2005, according to Novartis Pharma.
In October, after the criticism of its use of data emerged, Novartis said it had overhauled its management in Japan and set up a compliance advisory panel to prevent future problems.
Its pharmaceuticals head David Epstein said the company would work hard to rebuild the trust of Japanese customers.
(Reporting by Caroline Copley in Zurich and Chang-Ran Kim in Toyko; editing by Tom Pfeiffer)