You can find the official citation rules here.
Format:
Platform accessed, database accessed, publisher location: publisher; date accessed.
Example:
Lexi-Comp OnlineTM , Pediatric & Neonatal Lexi-Drugs OnlineTM , Hudson, Ohio: Lexi-Comp, Inc.; January 29, 2011.
To cite a LexiComp monograph in EndNote, see the screenshot below. NOTE: when entering an institution or company name into the "Author" field, be sure and put a comma at the end of the name as shown below. Otherwise, EndNote will assume it's a person's name and will try to turn it into a "lastname, initials" format in the generated citation.
Learn more about EndNote from our EndNote Online Guide.