How GW Pharmaceuticals Grows Cannabis to Make Consistent Prescription Medicine | Research

The takeaway

Producing pharmaceutical-grade cannabis medicine requires managing enormous natural variability in plant genetics, growing conditions, harvest timing, and processing methods.

Read this if you want to understand the challenges of turning cannabis into standardized prescription medicine.

Sativex was the first cannabis-based medicine approved in the UK

What the researchers found

Cannabis is an extremely inhomogeneous raw material, with cannabinoid ratios affected by genetics, growing conditions, storage conditions, maturity at harvest, and processing methods. GW Pharmaceuticals had to develop comprehensive quality control systems across all these variables to produce Sativex, the first cannabis-based medicine approved in the UK.

The company developed specific cannabis chemotypes (chemical varieties) to produce consistent THC and CBD ratios. The botanical considerations are particularly challenging because cannabinoid content varies across different parts of the plant, changes with maturity, and is affected by environmental conditions during growth.

Sativex was approved for treating spasticity due to multiple sclerosis and contains both THC and CBD along with other plant constituents. The pharmaceutical standardization process described represents a significant departure from the variability inherent in recreational or even most medical cannabis products.

Why it matters

The gap between recreational/medical cannabis products and pharmaceutical-grade cannabis medicines is enormous in terms of consistency and quality control. Understanding the challenges of standardizing cannabis helps explain why pharmaceutical development is difficult and why product-to-product variability remains a concern in the broader cannabis market.

The numbers in context

Sativex contains both THC and CBD. It was the first cannabis-based medicine approved in the UK for MS spasticity. Cannabis contains over 100 cannabinoids whose ratios must be controlled.

How the study worked

This is a descriptive review authored by a GW Pharmaceuticals researcher, detailing the company's approach to cultivating and processing cannabis for pharmaceutical use. It covers botanical considerations, genetic selection, growing protocols, harvesting, and quality control processes.

What this study cannot tell us

This review is written by a GW Pharmaceuticals employee and describes the company's proprietary methods. It is inherently promotional and does not compare their approach to alternative manufacturing methods. The focus is on process rather than clinical efficacy.

How to read the evidence

This is a descriptive industry review. It provides valuable process information but is not a clinical study.

When this study was published

Published in 2014. Since then, additional cannabis-based medicines (including Epidiolex) have received regulatory approval.

The bigger picture

As cannabis-based medicines move into mainstream pharmaceutical development, the challenges of standardizing a complex botanical product become apparent. The approach described here, controlling genetics, environment, and processing, represents the pharmaceutical industry's answer to cannabis variability, though it results in products very different from whole-plant cannabis.

Questions still open

Can other companies replicate this level of consistency? Does pharmaceutical standardization sacrifice beneficial components present in whole-plant cannabis? Will synthetic cannabinoids eventually replace plant-derived medicines?

Common questions

Why is cannabis so hard to standardize?

Cannabis produces over 100 different cannabinoids whose ratios change based on plant genetics, growing conditions, light exposure, harvest timing, and storage. Unlike most pharmaceutical raw materials, each plant is slightly different, making batch-to-batch consistency extremely challenging.

How does pharmaceutical cannabis differ from dispensary products?

Pharmaceutical cannabis undergoes rigorous quality control to ensure every dose contains exactly the specified amount of active ingredients. Most dispensary products have wider variability in cannabinoid content and may not undergo the same level of testing.

Read the original research

A review of the cultivation and processing of cannabis (Cannabis sativa L.) for production of prescription medicines in the UK.

Drug testing and analysis, 6(1-2), 31-8

View on PubMed ↗Publisher’s paper ↗

Citation

Potter, David J. (2014). A review of the cultivation and processing of cannabis (Cannabis sativa L.) for production of prescription medicines in the UK.. Drug testing and analysis, 6(1-2), 31-8. https://doi.org/10.1002/dta.1531