Baxter International Inc. (BAX), the maker of blood products and intravenous drugs, fell as much as 5.4 percent after an analyst said the company may be hurt by health insurer Aetna Inc. (AET)’s decision to favor a rival Grifols SA (GRF) treatment for immune system disorders. Aetna indicated it plans to consider Barcelona-based Grifols’s Gamunex the “preferred” brand of IVIG, a treatment for immune system disorders, said Matthew Prior, an analyst for Bank of America Merrill Lynch in Melbourne. The decision may limit use of other medications, including Baxter’s Gammagard, Prior wrote in an Oct. 12 note to investors. Baxter, based in Deerfield, Illinois, declined 1.8 percent to $55.08 at 1:32 p.m.