Pfizer Inc, which plans a $160-billion merger with Ireland-based Allergan Plc to slash its U.S. tax bill, on Jan. 1 raised U.S. prices for more than 100 of its drugs, some by as much as 20 percent, according to statistics compiled by global information services company Wolters Kluwer. Pfizer confirmed a 9.4 percent increase for heavily advertised pain drug Lyrica, which generated $2.3 billion in 2014 U.S. sales; a 12.9 percent increase for erectile dysfunction drug Viagra, which had 2014 U.S. sales of $1.1 billion; and a 5 percent increase for Ibrance, a novel breast cancer drug launched last year at a list price of $9,850 per month, or $118,200 per year.