Studies Highlight Threats and Opportunities of E-Prescribing Drug Codification

While standards have helped move health information exchange and interoperability forward, selected challenges remain. Two recently released studies in the Journal of Managed Care & Specialty Pharmacy and Journal of the American Medical Informatics Association examine deficiencies in e-prescribing drug name identifiers and recommend strategies for improving the quality of care.

Most electronic prescriptions issued in the United States adhere to standards developed by the National Council for Prescription Drug Programs (NCPDP). On Surescripts’ network alone, more than 1 billion electronic prescriptions are transmitted each year using the NCPDP’s SCRIPT standard.

The 10.6 version of the SCRIPT standard is the most widely used in the industry and is the primary standard recognized by the Centers for Medicare and Medicaid Services (CMS). According to the current standard, a prescription can be electronically transmitted from a provider to the pharmacy with only text being used to describe the prescription drug. In practice, however, a codified drug identifier is also transmitted in the e-prescription message.

While the National Drug Code (NDC) is the most commonly used codified drug identifier in e-prescribing, prescribers and pharmacists have expressed concerns about its capacity to reliably provide accurate and interpretable drug identities. As a result, another drug terminology system–RxNorm–has been suggested as an alternative to NDC that could improve e-prescribing quality and reduce the risk for misinterpretation and medication errors.

To further clarify the differences between RxNorm and NDC terminology and each study’s findings, we spoke with the authors of these studies to share their perspective:

Q.What were the main drivers for RxNorm’s creation and a need for its development?

Ajit Dhavle, Surescripts: The creation of RxNorm was motivated by the need for a single, standard, multipurpose terminology for representing medications. Various proprietary drug terminologies, while working well on their own, can present a barrier when medical information systems containing these varying names and codes need to be cross-linked or reconciled. Therefore many clinical information tasks can benefit from the use of a standard, interoperable terminology, such as RxNorm, for representing drug information, including the creation of electronic medical records (EMR), automated decision support, quality assurance, healthcare research, and mandatory reporting.

Q.How does RxNorm differ from NDC terminology?

Dhavle: RxNorm is a standardized, non-proprietary clinical drug nomenclature developed and maintained by the United States National Library of Medicine (NLM) to facilitate the electronic exchange of clinical health information between various systems that use different drug nomenclatures.  In contrast, NDCs were originally developed for Medicare drug reimbursement and inventory management purposes and are specific to a particular manufacturer/labeler product, and associated packaging information. Although the FDA publishes manufacturer-submitted NDCs and corresponding drug information in the NDC Directory, the accuracy of this source has been criticized due to incomplete submissions by manufacturers and / or delays in the entry of data.

Q.What were some of the issues brought to light with the NDC implementation study?

Vishal Amin, CVS Health: Our study quantified two major NDC e-prescribing implementation issues, namely:

• About one-third of all e-prescriptions included an unrepresentative NDC (obsolete, expired, repackaged or private label).  This finding is noteworthy because the receiving pharmacy system may not be able to recognize or process such a prescription thereby significantly hampering automation. Furthermore, this problem has the potential to result in patient harm if the NDC in the receiving system is associated with a different drug product.
• More than 0.2 percent or 2 million e-prescriptions contained a free-text drug description that pointed to a completely different drug concept than that associated with its NDC number.  With over 1 billion e-prescriptions transmitted on an annual basis, such discrepancies constitute a significantly greater threat to patient health and safety if not caught by the pharmacist during the prescription fulfillment process.

Q.What were some of the issues brought to light with the RxNorm implementation study?

Stacy Ward-Charlerie, Surescripts: The RxNorm terminology has been recommended as the preferred e-prescribing drug identifier by CMS and other organizations.   While very promising, opportunities to improve its implementation remain.  Although RxNorm adoption has ramped up considerably since this study was conducted, wide-scale usage is still lacking. Notable study findings include:  

• Nearly 98% of e-prescriptions could be accurately represented by the RxNorm terminology.  As a result, we recommend that NLM expand the scope of RxNorm so that it can cover all ambulatory e-prescriptions.
• Vendor implementation of RxNorm needs careful attention. In 0.06% or 600,000 of 1 billion e-prescriptions, we found the drug descriptions associated with the RxNorm unique concept identifier (RxCUI) and free-text drug description string pointed to a completely different prescription drug concept. Similarly, we found that 0.04% of drug descriptions associated with the NDC identifiers and RxCUIs pointed to completely different drug concepts.

Q.With respect to accurate drug identification, what does the ideal e-prescription of the future look like?

Michael T Rupp, Midwestern University: The ideal e-prescription would have an e-prescribing preferred name that clearly and unambiguously communicates the intent of the prescriber to the pharmacist and include two corresponding drug identifiers to ensure the exchange of accurate information:

• A representative NDC that is not obsolete, expired, repackaged or private label.
• An RxNorm unique concept identifier with a matching Term Type (SBD, SCD, BPCK or GPCK) when available.
• The free-text drug description and the drug descriptions associated with the NDC value and RxNorm RxCUI / Term Type from the message should all semantically match to prevent confusion and manual edits of the e-prescription by the pharmacy staff.

More information on each of the studies can be found below:

• Analysis of National Drug Code Identifiers in Ambulatory E-Prescribing, Journal of Managed Care & Specialty Pharmacy
• Evaluating the implementation of RxNorm in ambulatory electronic prescriptions, Journal of the American Medical Informatics Association