EndNote includes a special interface which allows users to connect to remote databases, including MEDLINE. 

WARNINGS: The direct interface allows only rudimentary searching. The assistance which Ovid offers in selecting terms, selecting subheadings, expanding categories, limiting searches to English, or Reviews is not available. You may lose a significant number of relevant articles. If you are performing a subject search, it is recommended that you use Ovid, and import the results into EndNote (see How do I download citations from Ovid for use in EndNote?).

An excellent use for the direct search would be for an author search, or to verify references for a manuscript, or to add a known reference.

To search OvidSP MEDLINE in EndNote X2-X4, click on the Online Search button or choose Online Search from the Tools menu.

Select Medline (OvidSP) from the list of connections. Click Connect.

Use the search box at the bottom of the EndNote library to search.