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Every endpoint and UI surface in MedDRA Explorer defaults to the most recent official release, but you can request historical snapshots when needed. This guide outlines the options and the precedence rules we enforce.

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When to override the default

  • Regulated workflows that must stick to the release in force when a study began.
  • Model validation where you benchmark classifiers against a fixed terminology snapshot.
  • Change analysis for QA or pharmacovigilance teams reviewing terminology updates version by version.

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Select a version via query parameter

Add a version query string to any GET endpoint: 
curl "https://api.meddra.co/codes?q=allergic reaction&version=28.0"
For POST /classify, include the version in the JSON body: 
{
	"description": "Facial swelling and shortness of breath within 20 minutes.",
	"version": "28.0"
}
Authentication reminder: include X-API-Key: sk-<API_KEY> whenever you call POST /classify.

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Use the X-MedDRA-Version header

When it’s easier to keep the URL consistent, supply a header instead: 
curl https://api.meddra.co/codes \
  -H "X-MedDRA-Version: 28.0"
This is especially convenient for SDKs or gateway configurations where you prefer to set default headers once.

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Precedence rules

  1. We look for a version value in the query string (for GETs) or in the JSON body (for POST /classify).
  2. If absent, we check the X-MedDRA-Version header.
  3. If neither is provided, we serve the latest release.
When both a query/body parameter and a header are present but disagree, we honour the parameter and log a diagnostic entry so you can catch misconfigurations in observability tooling.
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