It is necessary to define your audience before you can figure out how to reach them. For example Dr. Gerald Smith's book  "Alternative Treatments for Conquering Chronic Pain" was clearly targeted for the following audience.

1. The primary audience is the public
2. Dentists
3. Medical Doctors
4. Osteopaths and Chiropractors
5. Medical Organizations
6. Organizations and Foundations interested in the topic.
7. Educational Organziations
8. Research Organizations

Where do they hang out?