Connecting Drug and Product Information
A medication may seem like a single piece of information, but there is a lot that needs to be represented behind it. The drug, strength, dose form, manufacturer, and specific product can all become important depending on how that information is being used.
Interoperability is one of the most challenging areas of health IT, and medication information can be particularly difficult because the same medication needs to be understood in different ways. The active drug may be important for functions such as allergy and drug-drug interaction checking, while strength, route, and dose form help identify what has actually been ordered. Pharmacy, medication administration, inventory, and billing workflows may also need to identify the specific product being used.
This is one of the reasons medication coding does not come down to assigning one universal code to every drug. Different identifiers can represent different parts of the medication information while keeping those pieces connected. The code systems vary between countries, but RxNorm and National Drug Codes (NDCs) in the United States provide a useful example of how this works.
Different functions rely on different information
To help illustrate the different information involved, we can take a look at Benadryl. Its active drug is diphenhydramine hydrochloride (diphenhydramine HCl), which is manufactured in different strengths and dose forms. For example, you may see oral tablets, capsules, or liquids available in 25 mg, 50 mg, or other strength options.
If a hospital provider orders Benadryl for a patient, drug-drug alerts usually rely on active ingredient details, regardless of the manufacturer, strength, or form. If a patient has a documented allergy to diphenhydramine, the EHR needs to recognize that regardless of who manufactured the medication or whether the one being ordered is a tablet, capsule, or liquid.
For pharmacy to dispense the medication, information on strength and administration route are required. If the provider orders 25 mg to be given orally, there may be several products that could be used to fill that order. The hospital formulary may include a generic 25 mg diphenhydramine HCl tablet rather than the Benadryl brand. When the pharmacist verifies the order, the appropriate formulary product is associated so the item dispensed and ultimately documented on the medication administration record remains connected to the original order.
Traceability may require even more specificity. Knowing that a patient received a 25 mg diphenhydramine HCl oral tablet may not be enough. The same product may be sold in different packages, such as a 12- or 60-count retail bottle or a bulk or unit-dose package used by a hospital. If the recall is package or lot specific, the organization needs a way to determine whether it was supplied or administered to a particular patient.
These different levels of medication information help explain why a single identifier is typically not enough. Related code sets can support the drug information needed for clinical functions as well as the product information needed for inventory, dispensing, administration, and other operational activities.
RxNorm helps normalize drug information
RxNorm was developed by the U.S. National Library of Medicine to give systems a consistent way to identify drugs when different terminology is used. This is similar to how LOINC supports laboratory data. One system may use a local name for a lab test while another uses something different, but mapping both to the appropriate LOINC code provides a common reference for what the test represents.
RxNorm does the same type of thing with drug information. One system might use diphenhydramine hydrochloride while another uses diphenhydramine HCl. Mapping the terminology to RxNorm allows both systems to recognize that the information refers to the same active drug.
RxNorm also distinguishes clinically relevant differences such as strength and dose form. For example, two diphenhydramine HCl oral tablets with different strengths have different RxNorm Codes:
1049630 → Diphenhydramine HCl 25 mg oral tablet
1085945 → Diphenhydramine HCl 50 mg oral tablet
This gives systems a consistent way to identify the drug, strength, and dose form when medication information is exchanged. It does not identify the specific product, including details such as the manufacturer and package type. That requires another identifier, which is where the NDC comes in.
NDC identifies the product
In the U.S., the FDA-assigned NDC identifies the drug product, the labeler responsible for it, and how the product is packaged. Each NDC contains three segments:
Labeler: Typically the manufacturer or distributor responsible for the product
Product: The strength, dose form, and formulation associated with that labeler
Package: The package size and type
A 25 mg diphenhydramine HCl oral tablet produced by one manufacturer can therefore have a different NDC from an equivalent tablet produced by another. Different packages of the same product can also be identified separately, such as a 100 count value-size bottle at a retail pharmacy or package prepared for unit-dose use in a hospital.
This is where the two code sets connect. Several different products may contain the same drug in the same strength and dose form, so while they will have the same RxNorm code each one will have its own NDC. The systems can recognize what those products have in common without losing the information that distinguishes one product or package from another.
RxNorm → What drug, strength, and dose form is this?NDC → Which specific product and package is this?
Medication information needs to stay connected
Within an EHR, those relationships allow different functions to use the medication information they need. They become equally important when information moves between systems. A product identifier may provide the specificity needed for dispensing or traceability, but the receiving system may also need to understand the drug, strength, and dose form associated with that product.
The specific code sets used to support this vary around the world, which can make medication interoperability more complicated across jurisdictions. Regardless of the standards involved, the drug and product information still needs to remain connected so that medication data can continue to support clinical care as it moves through different systems and workflows.