RxClass (Drug Classifications) API

Look up drug classification hierarchies from NLM MED-RT.

Overview

RxClass provides standardized drug classification data from the NLM/VA MED-RT system. Classifications organize drugs by mechanism of action, physiologic effect, pharmacologic class, and more. FHIRfly provides fast lookups against the RxClass hierarchy, including class membership queries.

Endpoints

Method	Path	Description
GET	`/v1/rxclass/:classId`	Single class lookup
POST	`/v1/rxclass/_batch`	Batch lookup (up to 100)
GET	`/v1/rxclass/shapes`	List available response shapes
GET	`/v1/rxclass/:classId/members`	List drugs in a class

Single Lookup

Look up an Established Pharmacologic Class

Request

Node.js

const response = await fetch(
  "https://api.fhirfly.io/v1/rxclass/N0000175355",
  {
    method: "GET",
    headers: {
    "x-api-key": "YOUR_API_KEY",
  }
  }
);

const data = await response.json();
console.log(data);

Response

JSON

{
  "data": {
    "class_id": "N0000175355",
    "class_name": "Angiotensin 2 Receptor Blocker",
    "class_type": "EPC",
    "source": "FDASPL",
    "description": "Established Pharmacologic Class [EPC]"
  },
  "meta": {
    "legal": {
      "attribution_required": false,
      "citation": "NLM MED-RT via RxClass. Accessed 2026-03-01 via FHIRfly.",
      "license": "UMLS",
      "source_name": "RxClass"
    }
  }
}

Class Types

RxClass organizes drugs into multiple classification systems:

Type	Full Name	Source	Description
`MoA`	Mechanism of Action	MED-RT	How the drug works at the molecular level
`PE`	Physiologic Effect	MED-RT	The drug's effect on body processes
`EPC`	Established Pharmacologic Class	FDA SPL	FDA-designated pharmacologic class
`TC`	Therapeutic Category	VA	Therapeutic use categories
`SC`	Structural Class	MED-RT	Chemical structure classification
`PK`	Pharmacokinetics	MED-RT	Drug absorption, distribution, metabolism

Batch Lookup

Look up multiple class IDs in a single request (up to 100):

Look up multiple drug classes

Request

Node.js

const response = await fetch(
  "https://api.fhirfly.io/v1/rxclass/_batch",
  {
    method: "POST",
    headers: {
    "x-api-key": "YOUR_API_KEY",
    "Content-Type": "application/json",
  },
    body: JSON.stringify({
    "codes": [
      "N0000175355",
      "N0000000225"
    ]
  })
  }
);

const data = await response.json();
console.log(data);

Response

JSON

{
  "count": 2,
  "results": [
    {
      "input": "N0000175355",
      "class_id": "N0000175355",
      "status": "ok",
      "data": {
        "class_name": "Angiotensin 2 Receptor Blocker",
        "class_type": "EPC"
      }
    },
    {
      "input": "N0000000225",
      "class_id": "N0000000225",
      "status": "ok",
      "data": {
        "class_name": "Decreased Platelet Aggregation",
        "class_type": "PE"
      }
    }
  ],
  "meta": {
    "legal": {
      "license": "UMLS"
    }
  }
}

Batch with `shape=full`

When using shape=full on batch requests, the response includes meta.source with provenance information:

POST /v1/rxclass/_batch?shape=full

{
  "count": 2,
  "results": [
    {
      "input": "N0000175355",
      "class_id": "N0000175355",
      "status": "ok",
      "data": { "class_name": "Angiotensin 2 Receptor Blocker", "class_type": "EPC" }
    }
  ],
  "meta": {
    "source": {
      "name": "RxClass",
      "url": "https://rxnav.nlm.nih.gov/RxClassIntro.html",
      "version": "monthly",
      "fhirfly_updated_at": "2026-03-01T03:00:00Z"
    },
    "legal": {
      "license": "UMLS",
      "attribution_required": false
    }
  }
}

Class Members

Retrieve the drugs that belong to a specific class:

List drugs in Angiotensin 2 Receptor Blocker class

Request

Node.js

const response = await fetch(
  "https://api.fhirfly.io/v1/rxclass/N0000175355/members",
  {
    method: "GET",
    headers: {
    "x-api-key": "YOUR_API_KEY",
  }
  }
);

const data = await response.json();
console.log(data);

Response

JSON

{
  "data": {
    "class_id": "N0000175355",
    "class_name": "Angiotensin 2 Receptor Blocker",
    "member_count": 8,
    "members": [
      {
        "rxcui": "83818",
        "name": "valsartan",
        "tty": "IN"
      },
      {
        "rxcui": "52175",
        "name": "losartan",
        "tty": "IN"
      },
      {
        "rxcui": "29046",
        "name": "irbesartan",
        "tty": "IN"
      },
      {
        "rxcui": "321064",
        "name": "olmesartan",
        "tty": "IN"
      }
    ]
  },
  "meta": {
    "legal": {
      "license": "UMLS",
      "source_name": "RxClass"
    }
  }
}

The members endpoint returns all drugs classified under the given class, linked by RxCUI. Use this to discover drugs by their pharmacologic properties rather than brand or ingredient name.

Response Shapes

Control the level of detail in responses with the shape query parameter:

Shape	Description
`compact`	class_id, class_name, class_type
`standard`	+ source, description, parent classes
`full`	+ child classes, ingest metadata

# Minimal data
GET /v1/rxclass/N0000175355?shape=compact

# Standard data (default)
GET /v1/rxclass/N0000175355?shape=standard

# Full data with provenance
GET /v1/rxclass/N0000175355?shape=full

See Response Shapes for field details.

Required Scopes

rxclass.read - Single and batch lookups, class member queries

RxClass (Drug Classifications) API

Overview

Endpoints

Single Lookup

Look up an Established Pharmacologic Class

Class Types

Batch Lookup

Look up multiple drug classes

Batch with shape=full

Class Members

List drugs in Angiotensin 2 Receptor Blocker class

Response Shapes

Required Scopes

Cookie Preferences

Batch with `shape=full`