I'm in pharmaceuticals and all my jobs have come through recruitors. I always just tell them that I have already been submitted to that company. Once a company has your info either from you applying online or from an employee or recruitor they will not pay anyone else who gives them your info. Therefore it is not worth the second person's time to submit you.
When I was looking for a job I always worked with 5-15 recruitors just because they all have relationships with different companies, but I was always open with them that I was working with other people. Sticking with only one or two recruitors can really limit your options.