A pharmaceutical or biopharmaceutical drug's effects can be evaluated in terms of potency, which refers to the quantitative measurement of the biological activity of a given product or amount of drug (usually expressed in milligrams) needed to produce an effect, such as relief of pain or reduction of blood pressure. Simply put, potency determination is a measure of how powerful or strong the drug is.

Biological activity is a critical quality attribute; therefore, potency testing is an essential component of Quality Control in the manufacturing process. Potency tests, along with a number of other tests, are performed as part of product conformance testing, comparability studies, and stability testing. These tests are used to measure product attributes associated with product quality and manufacturing controls, and are performed to assure strength (potency) of products used during all phases of drug development and manufacturing.

Failure by the manufacturer to demonstrate the drug is meeting its pre-set FDA standards of potency or it is showing to be unstable during the manufacturing process will result in the non-release of products. A drug product is considered unstable when the drug substance (active ingredient) loses sufficient potency to adversely affect the safety or efficacy of the drug or falls outside of its labelled specifications. Drugs are considered stable if the active ingredient can maintain its strength at the level specified on the label for the maximum anticipated shelf-life.

To address the needs of rapid, selective, and accurate potency determination quantitative nuclear magnetic resonance (q-NMR) spectroscopy has been shown to be a single point replacement for routine development testing which previously involved several experiments and techniques, namely chromatography. Q-NMR has also proved a superior method for determining the purity of the reference standards used for analysis with assured metrological traceability such as standards for high pressure liquid chromatography (HPLC).

As all work in the pharmaceutical industry must meet the appropriate regulatory standards, it is important to note that traditional NMR and q-NMR is accepted by the International Conference on Harmonization (ICH).