Why aren't NDCs or J-codes used during clinical trials?

Investigational drugs in clinical trials are unapproved candidates without commercial packaging or retail distribution. They do not yet bill on insurance claims, so trial data managers use MedDRA and WHODrug to record safety data rather than billing identifiers.

What are the five levels of the MedDRA hierarchy?

MedDRA consists of: 1. System Organ Class (SOC), 2. High-Level Group Term (HLGT), 3. High-Level Term (HLT), 4. Preferred Term (PT), and 5. Lowest Level Term (LLT).

How do EDC systems perform automated medical coding?

Modern Electronic Data Capture (EDC) platforms use automated coding algorithms that compare investigator entries against MedDRA and WHODrug synonym lists, routing unmatched entries to human medical coders for manual review.

Clinical trial standards

How does medical coding work in clinical trials?

Clinically Reviewed by Editorial Board Last Reviewed: March 2026Standard: HIPAA 5-4-2 & CMS-1500

Short answer

In clinical trials, medical coding standardizes raw research data — such as adverse events, medical histories, and concomitant medications — using global regulatory dictionaries like MedDRA and WHODrug rather than healthcare billing codes.

Clinical trial coding vs healthcare reimbursement coding

Medical coding in clinical research serves a completely different objective from healthcare billing. While hospital and provider coding (ICD-10-CM, CPT, HCPCS Level II) focuses on insurance claims, fee schedules, and reimbursement, clinical trial coding focuses on patient safety, trial protocol standardization, and regulatory compliance.

During a clinical trial, investigator sites worldwide record patient observations in unstructured text. Medical coding transforms these free-text entries into standardized, universally understood alphanumeric codes stored in Electronic Data Capture (EDC) systems.

MedDRA: Coding adverse events and medical conditions

The Medical Dictionary for Regulatory Activities (MedDRA), maintained by the International Council for Harmonisation (ICH), is the global standard for coding adverse events (AEs), symptoms, and diagnoses in clinical trials.

MedDRA operates across a 5-tier hierarchy: System Organ Class (SOC) at the broadest anatomical level, down through High-Level Group Terms (HLGT), High-Level Terms (HLT), Preferred Terms (PT), and Lowest Level Terms (LLT). This multi-level structure allows biostatisticians and safety monitors to detect adverse safety signals at both granular and systemic levels.

WHODrug: Standardizing concomitant medications

The WHODrug Dictionary, maintained by the Uppsala Monitoring Centre (UMC), standardizes all prior and concomitant medications taken by clinical trial participants.

WHODrug maps trade names, active chemical ingredients, and Anatomical Therapeutic Chemical (ATC) classifications. This allows clinical data managers to assess potential drug-drug interactions and monitor compliance with protocol exclusion criteria.

From investigational candidate to commercial NDC and J-Code

Throughout Phase 1, Phase 2, and Phase 3 clinical studies, an investigational product operates under an FDA Investigational New Drug (IND) application, identified by protocol research codes.

Once a candidate proves safety and efficacy in Phase 3 trials and receives FDA approval (via NDA or BLA), it enters the commercial healthcare system. The manufacturer registers the product with the FDA to receive a National Drug Code (NDC), CMS assigns a permanent HCPCS Level II J-code for clinician administration, and the AMA designates CPT procedure codes for administration.

Common follow-ups

Why aren't NDCs or J-codes used during clinical trials?: Investigational drugs in clinical trials are unapproved candidates without commercial packaging or retail distribution. They do not yet bill on insurance claims, so trial data managers use MedDRA and WHODrug to record safety data rather than billing identifiers.
What are the five levels of the MedDRA hierarchy?: MedDRA consists of: 1. System Organ Class (SOC), 2. High-Level Group Term (HLGT), 3. High-Level Term (HLT), 4. Preferred Term (PT), and 5. Lowest Level Term (LLT).
How do EDC systems perform automated medical coding?: Modern Electronic Data Capture (EDC) platforms use automated coding algorithms that compare investigator entries against MedDRA and WHODrug synonym lists, routing unmatched entries to human medical coders for manual review.

Terms used here

MedDRAThe Medical Dictionary for Regulatory Activities: the global standard terminology used to code adverse events and medical conditions in clinical trials.Definition WHODrugThe international drug dictionary maintained by the Uppsala Monitoring Centre (UMC) used to standardize concomitant medications in clinical research.Definition Adverse event (AE)Any untoward medical occurrence in a clinical trial participant administered an investigational drug, regardless of suspected causality.Definition Electronic Data Capture (EDC)Software platforms used by clinical trial sites and sponsors to collect, validate, and manage patient case report form (eCRF) data electronically.Definition Investigational New Drug (IND)The FDA submission that permits an unapproved drug to be shipped across state lines for clinical study.Definition Phase 3Large confirmatory trials, usually randomised and controlled, that form the basis of an approval application.Definition