A composition for extending the half-life of a crystalline antibody, including synergistically effective amounts of a half-life-extending compound and a crystalline antibody. A composition for extending the half-life of a crystalline antibody including synergistically effective amounts of lactulose and a crystalline anti-PCSK9 antibody. A method of extending the half-life of a crystalline antibody, by administering a synergistically effective amount of a half-life-extending compound and a crystalline antibody to an individual, and extending the half-life of the crystalline antibody. A method of promoting antibody recycling by affecting a receptor for an antibody to recycle the antibody.
