A network of drugs: The New Zealand Medicines Terminology

Every drug that can be prescribed or purchased in New Zealand is recorded in the New Zealand Medicines Terminology, or NZMT. A single source of truth for both generic names and drug brands, the NZMT provides the standard approach to identifying medicines that are approved for use and available in New Zealand.

The structure of the NZMT

Most products sold in the New Zealand marketplace are distinguished by their unique product identifiers, and drug products are no exception. Unique product identifiers are assigned to all drug products and printed as barcodes by their manufacturers. The most commonly used product identifiers both in New Zealand and globally are Global Trade Item Numbers (GTINs).

In the NZMT, each specific branded and packaged drug product is referred to as a containered trade product pack (CTPP) which can be thought of as a unique product identifier for drugs equivalent to GTIN. There are over 18,000 CTPPs defined in the NZMT that represent all drug products used in New Zealand.

Two different CTPPs, such as Panadol 500 mg tablet: film-coated, 1000 tablets, blister pack (50055471000117105) and Panadol 500 mg tablet: film-coated, 1000 tablets, bottle (50149001000117104), can only differ by the type of packaging (container) used to dispense the same amount, dose, and form of a drug. The "container-independent" general term Panadol 500 mg tablet: film-coated, 1000 tablets also exists in the NZMT, and is an instance of a trade product pack (TPP). The upper level of the branded product "hierarchy" are the brand names themselves, known as trade products (TPs). The Panadol 500 mg tablet: film-coated, 1000 tablets (10521421000116105) and Panadol 500 mg tablet: film-coated, 150 tablets (10522331000116105) TPPs, for example, are both "children" of the trade product Panadol (10510491000116108).

In addition to branded drug products, the NZMT also includes generic substances and preparations which form the generic drug hierarchy similar to that of branded drugs. Medicinal products (MPs) such as paracetamol (10037191000116105) and paracetamol + codeine phosphate (10059411000116103) represent the top level of the generic "branch" or the NZMT while medicinal product packs (MPPs), e.g. paracetamol 500 mg tablet, 1000 (10037661000116108), identify more specific forms of generic drugs.

All TPPs are linked to corresponding MPPs. For example, the Panadol 500 mg tablet: film-coated, 1000 tablets (10521421000116105) TPP is considered an instance of the paracetamol 500 mg tablet, 1000 (10037661000116108) MPP. When multiple branded versions of an MPP are available, there are multiple TPPs linked to that single MPP.

The NZMT, SNOMED CT, and the Semantic Web

SNOMED Clinical Terms (SNOMED CT) is a comprehensive clinical terminology widely used in clinical information systems and electronic health records across the world. In SNOMED CT and its extensions, all medical concepts have unique and uniform numerical identifiers and form a large network of interconnected items.

The NZMT uses SNOMED CT's numbering system for concept IDs and therefore can be considered a drug extension of SNOMED CT. Every concept in the NZMT, regardless of whether it's an CTPP or MP, is "globally addressable" and can be uniformly linked to any other SNOMED CT concept.

Every individual concept in SNOMED CT is represented by a uniform numerical ID which has a corresponding URI in the Semantic Web. For example, the canonical URI for the Myocardial infarction (22298006) concept from SNOMED CT is http://snomed.info/id/22298006. Similarly, the paracetamol (10037191000116105) MP from the NZMT can be represented by the http://snomed.info/id/10037191000116105 URI.

Bottom line

A register of canonical identifiers for all drugs used across the New Zealand health sector, the NZMT is essential for enabling cross-compatibility of different drug inventories, clinical information systems, and electronic health records. The NZMT's network of interlinked drug concepts includes both generic and branded products and is compliant with SNOMED CT.