The VisualDX corporate recommendation does not necessarily follow the citation style guidelines that you may need for your class assignments or for publication of a manuscript or book. Please consult the appropriate style guide to cite each topic as a chapter in an electronic book titled VisualDx with editor Lowell A. Goldsmith. There are no page numbers, and publication year should be the current year.
Example:
Papier A, Craft N, Tharp MD, Shear N. Cocaine Levamisole Toxicity. In: Goldsmith LA, ed. VisualDx. Rochester, NY: VisualDx; 2013. URL: http://www.visualdx.com/visualdx/visualdx6/getDiagnosisText.do?moduleId=14&diagnosisId=54687&view=text. Accessed October 29, 2013.