Description
Query the FDA Global Substance Registration System (GSRS) API.
Description
Provides functions to query the FDA Global Substance Registration System (GSRS) REST API (<https://gsrs.ncats.nih.gov/api/v1/>). Enables programmatic access to substance records, UNII identifiers, synonyms, external codes, and chemical structures for over 170,000 registered substances.
README.md
rgsrs
Tidy R client for the FDA Global Substance Registration System (GSRS) REST API. Retrieve substance metadata, synonyms, cross-reference codes, and chemical structure information for any of the 170 000+ registered substances.
No API key required.
Installation
# install.packages("pak")
pak::pak("c1au6i0/rgsrs")
Functions
| Function | Description |
|---|---|
gsrs_search() | Free-text or Lucene-syntax search |
gsrs_substance() | Substance metadata by UNII (vectorised) |
gsrs_names() | All registered synonyms for a UNII |
gsrs_codes() | Cross-reference codes for a UNII, with optional code_system filter |
gsrs_unii_from_name() | Resolve a substance name to its UNII |
gsrs_structure() | Chemical structure data (SMILES, formula, MW, InChI, …) by UNII |
gsrs_structure_search() | Substructure / similarity / exact search by SMILES |
gsrs_chem_info() | Chemical structure info from any identifier: name, CAS, UNII, InChIKey, or SMILES |
gsrs_hierarchy() | Parent/child relationship tree for a UNII |
gsrs_all() | Convenience wrapper: substance + names + codes + structure + hierarchy |
gsrs_browse() | Page through the full GSRS substance catalogue |
gsrs_vocabularies() | Retrieve controlled vocabulary terms |
write_dataframes_to_excel() | Write a named list of data frames to .xlsx |
Usage
library(rgsrs)
# Search
gsrs_search("aspirin", top = 5)
# Fetch by UNII (aspirin = R16CO5Y76E)
gsrs_substance("R16CO5Y76E")
# All synonyms
gsrs_names("R16CO5Y76E")
# Cross-references – all systems
gsrs_codes("R16CO5Y76E")
# Cross-references – CAS only
gsrs_codes("R16CO5Y76E", code_system = "CAS")
# Name → UNII
gsrs_unii_from_name(c("aspirin", "ibuprofen"))
# Chemical structure info by name
gsrs_chem_info(c("aspirin", "ibuprofen"), type = "name")
# Chemical structure info by CAS number
gsrs_chem_info(c("50-78-2", "15687-27-1"), type = "cas")
# Chemical structure info by UNII
gsrs_chem_info("R16CO5Y76E", type = "unii")
# Chemical structure info by InChIKey
gsrs_chem_info("BSYNRYMUTXBXSQ-UHFFFAOYSA-N", type = "inchikey")
# Chemical structure info by SMILES (exact match)
gsrs_chem_info("CC(=O)Oc1ccccc1C(=O)O", type = "smiles")
# Everything at once
out <- gsrs_all("R16CO5Y76E")
str(out, max.level = 1)
All functions accept a verbose argument (default TRUE) and return tidy data frames with a query column tracking the input identifier. Failed lookups return NULL with a warning rather than throwing an error.
License
MIT © 2026 Claudio Zanettini.