It is important to note that each database has some degree of specialization.
For instance, while EMBASE has listed more recent medicines and novel drugs as terms in Emtree, MeSH offers a broader range of subheadings.
If you conduct a literature search in EMBASE or MEDLINE, you should be aware of the differences in the establishment of subject headings.
MEDLINE contains more than 26.000 MeSH-terms with 83 subheadings and 213.000 synonyms whereas EMBASE has over 60.000 Emtree-terms (of which more than 30.000 are drug and chemicals) with 78 subheadings (64 are drug subheadings including 47 routes of drug administration) and 260.000 synonyms (over 175.000 drug synonyms).
You see that EMBASE focuses more on drugs and chemicals whereas MEDLINE offers a lot of publications in the fields of dentistry, nursing and veterinary medicine.
So choose wisely – depending on your field of research.
For instance – what if you are not looking for a clinical study with a drug, but rather with a non-drug intervention?
Michaleff et al. rated PubMed on the third and EMBASE on the fourth rank of databases when it comes to searching for randomized controlled trials in the field of physiotherapy.
They ranked the Cochrane Central Register of Controlled Trials (CENTRAL) first and a physiotherapy-specific database (Pedro) second.
In this search scenario, the evidence based medicine quest for identifying all available evidence suddenly got more complicated.
Research institutions but also regulatory and reimbursement agencies, thus, tend to request a search at least in MEDLINE AND EMBASE (and quite often now CENTRAL as well).