The short answer is yes, in the US a new use for an existing product that is ``new, useful, and non-obvious'' (as the patent law requires/defines) may be patented. That is, a new use may not be precluded from being patented simply because it is a new use for an existing product.
In the United States, there are three types of patents, all governed by the U.S. Patent and Trademark Office (USPTO): utility, design, and plant. Chemical patents can protect chemical compounds, compositions of matter, methods of making the chemical compound or composition, and methods of use.
What cannot be patented? a discovery, scientific theory or mathematical method, an aesthetic creation, a scheme, rule or method for performing a mental act, playing a game or doing business, or a computer program, a presentation of information,