Biomedical literature reviews always require database searches because...
Major biomedical databases include Medline, PubMed, Embase and PsycInfo. More information here.
Depending on your topic these databases may be enough. However you may also need to search:
Before staring to search make sure you have a clear statement of your question. This allows you to target your search to the most relevant material.
For advice on how to search visit our Guide to literature searching.
Searching is a iterative process, not a one off task.
As you find and review material new possibilities become apparent...