Querying Openfda Labels

Querying OpenFDA drug labels, NDC, and recalls

Once OpenMed has pulled a drug name out of a note, you often need authoritative product facts: the boxed warning, approved indications, dosage form / route, package NDC codes, and whether the product is under recall. The FDA's OpenFDA API exposes the Structured Product Labeling (SPL), the NDC directory, and enforcement (recall) reports — all public and free.

This skill is enrichment: it attaches regulatory facts to an extracted drug. It is not clinical decision support — a label lookup informs a human, it does not prescribe.

When to use

• You extracted a drug and need its boxed warning or indications for display, alerting, or expectedness checks.
• You need NDC package codes, dosage form, or route for a product.
• You want to know if a drug/lot is under an open recall (enforcement).
• You want to map a brand name to its generic ingredient and RxCUI via the label's openfda block.

The three endpoints

No key needed to try it (240 req/min, 1,000/day per IP). A free api_key= raises the daily cap to 120,000.

Quick start (real OpenFDA queries)

import requests

def openfda(endpoint: str, search: str, limit: int = 1) -> list[dict]:
    url = f"https://api.fda.gov/drug/{endpoint}.json"
    r = requests.get(url, params={"search": search, "limit": limit}, timeout=30)
    if r.status_code == 404:        # OpenFDA returns 404 for zero matches
        return []
    r.raise_for_status()
    return r.json().get("results", [])

# 1) Label: boxed warning + indications for a generic drug.
label = openfda("label", 'openfda.generic_name:"warfarin"')
if label:
    rec = label[0]
    print("Boxed warning:", rec.get("boxed_warning", ["(none)"])[0][:200])
    print("Indication:", rec.get("indications_and_usage", ["(none)"])[0][:200])
    print("RxCUI:", rec.get("openfda", {}).get("rxcui"))

# 2) NDC: package codes, form, route.
ndc = openfda("ndc", 'generic_name:"warfarin"', limit=5)
for rec in ndc:
    print(rec["product_ndc"], rec.get("dosage_form"), rec.get("route"))

# 3) Enforcement: open recalls for a product.
recalls = openfda("enforcement",
                  'product_description:"warfarin"+AND+status:"Ongoing"', limit=5)
for rec in recalls:
    print(rec["classification"], "-", rec["reason_for_recall"][:120])

Workflow

1. Normalize the drug name first. Use openmed.analyze_text to get the span, then prefer the RxNorm ingredient (see normalizing-rxnorm) as your query term — openfda.generic_name and the NDC generic_name index on the ingredient, so a normalized name hits far more records than raw note text.
2. Query /drug/label with openfda.generic_name:"<ingredient>" (or openfda.rxcui:"<rxcui>" for an exact product). Read boxed_warning, indications_and_usage, warnings_and_cautions.
3. Query /drug/ndc for package-level codes, dosage form, and route.
4. Query /drug/enforcement filtered to status:"Ongoing" to surface open recalls; gate alerts on classification (Class I = most serious).
5. Cache results — labels change rarely; you do not need to re-query per note.
6. Attach the facts to the extracted drug keyed by RxCUI/NDC for traceability.

Hand-off to / from OpenMed

OpenMed's analyze_text returns a dict; result["entities"] items carry text, label, confidence, start, end.

• From extracting-clinical-entities: Pharmaceutical/Chemical entities are the query seeds. From normalizing-rxnorm: pass the RxCUI to openfda.rxcui:"..." for an exact label match.
• To reporting-adverse-events: the boxed warning / indications support an expectedness judgment (is this reaction labeled?). To detecting-pv-signals: confirm whether a disproportionality signal is already on-label before escalating.
• OpenMed runs NER on-device; only a de-identified drug name or RxCUI leaves the process to hit OpenFDA. Never send a raw note containing PHI to the API — de-identify with openmed.deidentify first if you must derive the query from patient text.

Edge cases & gotchas

• OpenFDA returns 404 for an empty result set, not an empty results list — handle it as "no match" (the helper above does).
• Multi-value fields are lists. boxed_warning, indications_and_usage, and most SPL sections are arrays of strings (rec["boxed_warning"][0]). Many products have no boxed warning — the key is simply absent.
• Brand vs generic. openfda.brand_name and openfda.generic_name differ; query the generic (ingredient) for coverage, the brand for a specific product.
• Labels are SPL snapshots, not real-time. OpenFDA mirrors DailyMed SPL; a brand-new labeling change may lag. For the definitive current label, cross-check DailyMed.
• NDC formats vary (product_ndc is the 2-segment labeler-product code; package NDCs add a third segment). Normalize before joining to claims data.
• Recall status is one of Ongoing, Completed, Terminated — filter to Ongoing for active risk; classification Class I > II > III by severity.
• Public and free, but rate-limited. Register a free key and cache; do not hammer the API per-note in a batch pipeline.

Standards & references

• OpenFDA drug label API: https://open.fda.gov/apis/drug/label/
• OpenFDA NDC directory API: https://open.fda.gov/apis/drug/ndc/
• OpenFDA drug enforcement (recalls) API: https://open.fda.gov/apis/drug/enforcement/
• OpenFDA query syntax & rate limits: https://open.fda.gov/apis/query-syntax/ , https://open.fda.gov/apis/authentication/
• FDA Structured Product Labeling (SPL): https://www.fda.gov/industry/structured-product-labeling-resources
• DailyMed (authoritative labels): https://dailymed.nlm.nih.gov/dailymed/