An active pharmaceutical ingredient (API), also called the drug substance or, in EU law, the active substance, is the substance in a medicine that is meant to produce its therapeutic effect. The international GMP guide for APIs, ICH Q7, defines it as any substance or mixture intended for use in making a drug product that becomes the product’s active ingredient, and that is meant to furnish pharmacological activity or another direct effect in diagnosing, curing, mitigating, treating or preventing disease, or to affect the structure and function of the body. Everything else in the finished medicine, apart from the packaging, is an excipient.
The formal definitions side by side
| Term | Definition and source | Illustrative example |
|---|---|---|
| API / active substance | Substance intended to become the active ingredient of a medicinal product (ICH Q7; Directive 2001/83/EC) | Purified cannabidiol used to make an oral solution |
| Excipient | Any constituent of a medicinal product other than the active substance and the packaging material (Directive 2001/83/EC) | A carrier oil or flavouring in that solution |
| Drug (medicinal) product | The dosage form in its final immediate packaging intended for marketing (ICH Q7) | The labelled, filled bottle |
| Intermediate | Material produced during API processing that undergoes further molecular change or purification before it becomes an API (ICH Q7) | A crude extract awaiting purification |
| API starting material | Raw material, intermediate or API used to produce an API and incorporated as a significant structural fragment (ICH Q7) | Mainly relevant to synthetic routes |
The EU wording adds that the active substance is meant to exert a pharmacological, immunological or metabolic action, restoring, correcting or modifying physiological functions, or to make a medical diagnosis. The key idea in both texts is intent: a substance is an API because of the role it is given in a medicinal product.
Which GMP rules apply to an API
APIs have their own GMP guide. In the EU it is Part II of EudraLex Volume 4, “Basic requirements for active substances used as starting materials”. The PIC/S guide also places API rules in Part II, and PIC/S took that text from ICH Q7, which it adopted in 2001. The scope of ICH Q7 covers APIs made by chemical synthesis, extraction, cell culture or fermentation, recovery from natural sources, or any combination of these. Extraction and natural sources are therefore squarely inside it, which matters for anyone isolating cannabinoids from plant material.
ICH Q7 also contains a table mapping the steps of different kinds of API manufacture. For an API extracted from plant sources, and for herbal extracts used as an API, the chain runs from collection of plants through cutting and initial extraction to purification, physical processing and packaging. The same table lists an “API consisting of comminuted or powdered herbs”, which already tells you that a plant material can, in some settings, be the API. The guide does not apply to steps before the defined API starting material is introduced.
When a cannabinoid is an API
The clearest cases are single, defined cannabinoid substances used to make an authorised medicine:
- Dronabinol, a synthetic delta-9-THC, is the active ingredient in the US products Marinol and Syndros.
- Nabilone, a synthetic compound with a structure similar to THC, is the active ingredient in Cesamet.
- Cannabidiol: the US Food and Drug Administration describes Epidiolex as containing a purified form of the drug substance CBD.
Pharmacopoeial standards fit the same picture. The European Pharmacopoeia adopted monographs for Cannabis flower and for Cannabidiol isolated from Cannabis sativa L., with an implementation date of 1 July 2024. A monograph sets quality requirements; it does not by itself make a batch an API. That status comes from how the material is used and the GMP under which it is made.
Is cannabis flower an API?
Not in the narrow sense of a single defined molecule, but the accurate answer is that it depends on use, and the guides say so. ICH Q7 notes that the legal classification of a material as an API varies around the world, and that where a material is classified as an API in the country where it is made or used, it should be manufactured to the guide. The EU and PIC/S herbal annex (Annex 7) is more direct: the GMP classification of herbal material depends on how the manufacturing authorisation holder uses it, and it may be classified as an active substance, an intermediate or a finished product.
In practice that gives three common situations:
- Flower as the finished product. Dried flower dispensed to patients is the medicine itself, not an ingredient going into one.
- Flower as a starting material. Flower that will be extracted is herbal material at the start of an API or intermediate process.
- Flower as the active substance of a herbal product. Comminuted or powdered herb can be the declared active substance where the product and the jurisdiction treat it that way.
Annex 7’s table also marks where agriculture ends: cultivation, collection and harvesting fall under good agricultural and collection practice (GACP), and GMP applies to the further cutting and drying steps.
Common mistakes
- Calling any isolate an API. A cannabinoid isolate supplied for medicine manufacture is expected to be made under API GMP (EU or PIC/S Part II, based on ICH Q7). Purity alone does not make it an API.
- Treating excipients as irrelevant. They are part of the medicinal product, and EU and PIC/S rules require excipients and their suppliers to be controlled on the basis of a formalised quality risk assessment.
- Assuming high-grade flower is automatically an API. It may be a finished product, a starting material or an active substance, depending on use.
- Mixing up the abbreviation. In pharmaceutical documents API means active pharmaceutical ingredient, not an application programming interface.
- Ignoring national classification. A material treated as an API in one country may be regulated differently in another.
Classification is decided case by case by the competent authority of the market you supply, so check its current rules and ask it directly when a material sits on the boundary.