GlaxoSmithKline PLC, the world''s second largest drug maker by revenue, has posted a fourth-quarter loss after taking a massive charge to provide for U.S. litigation over its diabetes drug, Avandia, according to the Associated Press. Glaxo on Thursday posted a net loss of 690 million pounds ($1.12 billion) for the three months to Dec. 31, compared with a profit of 1.63 billion pounds a year ago. Revenue dropped 13 percent to 7.19 billion pounds, but the company is reinstating its share buyback program. Glaxo took a 2.2 billion pound charge to settle claims relating to Avandia and past U.S. sales practices. In September, European regulators ordered Avandia off the market and the U.S. Food and Drug Administration restricted its use because of evidence that the drug increased the risk of heart attacks.