How to search ClinicalTrials.gov for trials listed under alternate names or synonyms for a compound

1. Understand what ClinicalTrials.gov already does for synonyms

ClinicalTrials.gov parses user queries for UMLS concepts and automatically rewrites queries to include synonyms and alternative spellings, so a plain keyword search will often surface records listed under different names for the same concept without extra effort ^{[2] [3]}; library guides and institutional pages confirm that the site’s simple and advanced searches “automatically include synonyms” for entered terms ^[1].

2. Start with the site’s simple search but watch its blind spots

Using the main search box or the simple condition/intervention fields triggers ClinicalTrials.gov’s synonym expansion and recommended-term lists as text is entered, which makes the simple path effective for many queries ^{[1] [7]}; however, researchers should be aware that the automatic expansion is always applied and users cannot choose to require an exact phrase match through that mechanism, a limitation highlighted in analyses of the registry’s metadata ^[2].

3. Use Advanced Search and search operators when precision matters

For more control, the Advanced Search and expert/expert-search pages give fielded queries and filters that help narrow results by specific intervention, condition, or identifier, and the ClinicalTrials.gov search operators documentation should be consulted to construct complex queries that combine terms, dates, locations and identifiers ^{[4] [8] [9]}.

4. Build redundancy: search multiple synonyms, trade names and identifiers

Systematic-review guidance recommends structuring searches to cover one concept with a broad range of synonyms and related terms to maximize sensitivity, meaning explicit lists of generic names, brand names, chemical names and registry identifiers should be used in concert with ClinicalTrials.gov’s own expansion to catch records that might avoid harmonized metadata ^{[5] [6]}.

5. Check raw metadata and external resources for unharmonized records

Scholarly analyses warn that unharmonized values persist in ClinicalTrials.gov’s raw metadata—synonym expansion is applied only in the portal’s search engine and cannot be relied on to expose all hierarchical relationships or to allow users to opt out of synonym expansion—so reviewing trial records’ intervention and other raw fields and consulting ontology resources (e.g., MeSH/RxNorm via BioPortal) helps verify whether alternate names are present in the underlying data ^[2].

6. When a trial might be listed under a corporate or obscure label, widen the net

Practical advice from registry-search experts is to search at least ClinicalTrials.gov and meta-registries such as WHO ICTRP, and to use external sources like PubMed, sponsor pages or trial identifiers found elsewhere (e.g., NCT numbers) to locate trials when a compound appears under proprietary or legacy nomenclature—this cross-checking reduces missed records ^{[6] [5]}.

7. Verify findings and document the search strategy

Because ClinicalTrials.gov’s engine always includes detected synonyms and users can’t force exact-only matching, records retrieved should be inspected individually to confirm relevance, and searchers should document the exact query terms, fields used and dates searched—this follows best practice for reproducible trial searching and systematic reviews ^{[5] [6]}.

8. Know the limits of available guidance

Guidance and tools exist on ClinicalTrials.gov for constructing complex queries and using advanced features, but the public-facing documentation does not provide a fully detachable synonym list or a way to browse the MeSH hierarchy from an entered query, and some issues—such as whether a specific unpublished synonym appears only in raw metadata—may require manual checks or querying other registries ^{[8] [2] [4]}.