Proposed Change to Drug Concept Model

Roger believes that there is a fair level agreement that there are four levels of granularity in the classification of drugs for EMR purposes.

Four levels of granularity for drugs

• Level 1: Category
  • Most general (e.g. Pain Medication, HIV Anti-retrovirals) which is used to narrow the universe of drugs.  In OpenMRS, concept sets and, in the future, order sets, can be used to groups orderables into categories.
• Level 2: Active Ingredients
  • What the doctor is trying to specify for the patient.
• Level 3 Active Ingredients plus strength and form
  • Strength (the amount or concentration of each active ingredient in the drug) and form (tablet, liquid, intravenous fluid, etc.).  This is what should be on the prescription, along with quantity, frequency, refills and other instructions; this should be stored in the EMR.
  • Level 3 is the level at which a facility's formulary (the list of drugs it keeps available) is specified.
• Level 4 Dispensing and Administration
  • Level 3 plus manufacturer and lot number.  This is what the pharmacist/nurse actually dispenses/administers and should be recorded in the pharmacy system (outpatient) or drug administration record (inpatient).

Levels 2 and 3 are based on the organization of a standard nomenclature known as RxNorm, and other standard vocabularies also focus on these levels.  Names in the standard vocabularies are specified as chemical names (e.g. at level 2, stavudine/lamivudine/nevirapine), although they may be known at the facility otherwise (e.g. d4T/3TC/NVP or Triomune or Regimen 1a).  We try to encourage people to use the standard nomenclature, with other names maintained as synonyms.  We do this by guidance in the wiki and by encouraging the use of the MVP concept dictionary.  But we don't require it or validate against it.  While in the past we may have had multiple entries for the same clinical drug in the drug table under different names, it is our current expectation that each clinical drug will appear only once as a drug table entry or formulary concept, with other names being synonyms; this is to support links with pharmacy systems and alerting.

If a facility wants the fully-specified name (at level 3) to be Triomune 30 rather than stavudine/lamivudine/nevirapine 30mg/150mg/200mg, we allow it (at least as a synonym).  If a facility wants to have separate entries for Triomune and stavudine/lamivudine/nevirapine, it is done through synonyms.  We allow the same name to be used, at least as a synonym, at level 2 and level 3; however, all orders use level 3, because only at level 3 is there a drug table or formulary concept subclass.  In general, our approach has been for the most part to allow the clinic to go on doing what it has been doing, even though we (and substantially all the authoritative literature) are in agreement that prescribing at level 3 using standard ingredient names and strengths is the best at reducing drug administration errors; however, it is up to the system administrator to assure that appropriate drug concepts, drug table entries/formulary concepts, and synonym definitions exist to support the desired use.

There has been a fair amount of discussion about combination drugs.  We want to provide the capability of specifying in strongly-typed fields the strength of each ingredient of a combination drug without either overcomplicating the entry of single-ingredient drugs or requiring a facility to do so.  In this regard, it should be noted that each ingredient references a level 2 concept and adds strength (value and units) to it.