On the resources page, I have posted an excel spreadsheet that includes ISMP Tallman drug names and the RxNorm CUIs they are directly and indirectly related to. The first tab is the ISMP Tallman names and the RxNorm ingredients (TTY=IN) and brand names (TTY=BN). The second tab lists the relationships between the ISMP Tallman names and more granular RxCUIs. This was done by creating links based on the RXNREL table from the ingredient and brand names to their related concepts.
This uses the August 2010 RxNorm data and the latest ISMP Tallman drug names.
Here is my disclaimer - Use this file at your own risk. If you find any issues with it or have any questions, please let me know.
If you would like these in a pipe delimited test file format, with instructions, you need to email us and let us know who you are so that we may stalk you and fill you email inboxes with spam (not really).
If you find this useful, please let me know. We are considering maintaining this with each RxNorm update cycle.
For more information on the Institute for Safe Medication Practices go here: http://www.ismp.org/
For more information on RxNorm go here: http://www.nlm.nih.gov/research/umls/rxnorm/
For more information on interoperability, clinical decision support or clinical architecture go here: http://www.clinicalarchitecture.com (Wait... you already are here...)
When dealing with any terminology domain, to establish a
working understanding, you need to get a handle on the anatomy of a term within
the domain. For example, if you are
looking at a catalog of automobiles you quickly see a pattern that revolves
around the vehicle make, model, production year and other characteristics that
identify the vehicle to the required level of granularity. Regardless of the domain, the pattern
typically becomes broken down into primary characteristics, secondary
characteristics and modifiers. The
primary characteristic is the core of information that is absolutely essential
to the meaning of the term. In other
words, if you began stripping off characteristics the primary characteristics
is where you say ‘when’ so that the term is not rendered ambiguous in the
domain. In our automobile example there
are, arguably, a couple of primary characteristics: the make and model. If someone asks you what you drive you typically
tell them the make and model (unless the model strongly implies the make or you
like bragging about the options package…).
The model year, edition and options are secondary characteristics that
further define the vehicle and the color and other minutiae could be considered
modifiers (unless it is purple).
In the medication domain, the primary characteristic is the
list of ingredients, more specifically the list of active ingredients. Active ingredients drive the use of
medication concepts and, like with the car example, most people when asked
about their medications respond with the active ingredients or the brand name
synonym for the active ingredients. For
medications the implied route, dose form, strength are secondary
characteristics that are relevant but not always necessary.
The Inactive
Ingredients are Inactive… or ARE they?
Active and inactive ingredients typically both live together
in the domain of substances (or ingredients).
Whether an ingredient is active or inactive is, in most cases, a role
that the ingredient plays as opposed to what the ingredient is. This post is mostly about active ingredients,
but it is worth a few minutes to talk about inactive so that, and an
implementer, you understand the conceptual differences and the limitations of
the notion of an inactive ingredient when you encounter it in the wild.
The difference between an active and inactive ingredient is
subtle to the non-pharmacist. Typically
the active ingredients are the substances that define the medication, while the
inactive ingredients are excipients that are introduced in the manufacturing of
the drug product OR ubiquitous essence of life ingredients like ‘water’
that do not factor into the medications function. If you refer to the medication continuum in
the previous post, you will note that inactive ingredients do not participate
in the abstract or dispensable generalizations.
Since inactive ingredients are, for the most part, introduced by the
manufacturing process, any attempt to introduce them into higher level
generalizations is risky as it can create false alerts and worse missed alerts
(Which is the topic of another post and covered to a small degree in my ‘allergy
rule of thumb’ post).
Some may argue that if an inactive ingredient is present in
all manufactured forms of a drug you can represent is at a higher level
generalization for that particular situation.
I would argue that stretching rules of the composition of a terminology
to accommodate a few exceptions is not worth compromising the terminology’s
consistency. You need to know that
active ingredients are always active ingredients, diverging from that path
leads to the scary woods of unintended consequences.
You may encounter what looks like an inactive ingredient in
an active ingredient list. This is
either: (A) a valid active ingredient in that particular circumstance, (B)
introduced because it is clinically relevant and there is no other way for the
terminology to deal with this, or (C) it is junk DNA left over from a bygone
era. In any case, you must treat it like
an active ingredient: avoid eye contact and sudden movements. This is discussed more later in this post.
Let’s talk about active ingredients.
The Ingredient Set
Every valid medication concept (I am looking at YOU
medical devices…) has one or many active ingredients that make up its primary
characteristic. This may be referred to
as an ingredient set, ingredient list, generic drug or the formulation (ingredient
set in the medication concept continuum).
In fact, most every drug compendia has a concept that represents this
level. This is important as that defines
the set of valid active ingredient combinations. Most, if not all, drug
concepts in a medication hierarchy point back to this type of concept. These ingredient sets break down into a list
of individual ingredients.
Base ingredients
A single ingredient can represent a base ingredient or a
variation of a base ingredient. This is
significant because a variation of a base ingredient is related to the base
ingredient but can have significant differences (which I will not get into here…
ask you local pharmacist). To illustrate
this, consider the following table of
RxNorm ingredients that start with ‘Erythromycin’:
|
RXCUI
|
SAB
|
TTY
|
STR
|
|
4053
|
RXNORM
|
IN
|
Erythromycin
|
|
4055
|
RXNORM
|
IN
|
Erythromycin Estolate
|
|
4056
|
RXNORM
|
IN
|
Erythromycin Ethylsuccinate
|
|
24346
|
RXNORM
|
IN
|
Erythromycin Gluceptate
|
|
24347
|
RXNORM
|
IN
|
erythromycin lactobionate
|
|
24351
|
RXNORM
|
IN
|
erythromycin stearate
|
|
236847
|
RXNORM
|
IN
|
ERYTHROMYCIN STINOPRATE
|
In this list you can see the base ingredient of ‘Erythromycin’
and the variations (or different salt forms of Erithromycin in this example). In most cases the variations of a base
ingredient are clinical equivalent to the base ingredient and add not
additional clinical value other than accurately describing the variation of the
ingredient in a specific formulation.
Some compendia have only base ingredients, Some have base and variations
and some have defined relationships between the variation and the base.
This information can come into play when processing clinical
rules so you need to be aware of it. For
example a clinical rule may only be attached to the base ingredient so you need
to use the relationship from the variation to the base ingredient to activate the
rule.
In some situation a ingredient variation may represent
something other than a salt form of the base.
Here are some examples from RxNorm of non-salt variations:
|
RXCUI
|
SAB
|
TTY
|
STR
|
|
352374
|
RXNORM
|
IN
|
drotrecogin alfa
|
|
353106
|
RXNORM
|
IN
|
drotrecogin alfa (activated), lyophilized
|
|
RXCUI
|
SAB
|
TTY
|
STR
|
|
797550
|
RXNORM
|
IN
|
Immune Globulin (Human)
|
|
617615
|
RXNORM
|
IN
|
Immune Globulin Subcutaneous (Human)
|
In some cases there may be no base ingredient – only variations:
|
RXCUI
|
SAB
|
TTY
|
STR
|
|
17609
|
RXNORM
|
IN
|
aluminum acetate
|
|
89858
|
RXNORM
|
IN
|
Aluminum carbonate
|
|
17610
|
RXNORM
|
IN
|
aluminum chlorhydrate
|
|
46241
|
RXNORM
|
IN
|
aluminum chloride
|
|
17611
|
RXNORM
|
IN
|
Aluminum chloride hexahydrate
|
|
612
|
RXNORM
|
IN
|
Aluminum Hydroxide
|
|
81948
|
RXNORM
|
IN
|
Aluminum Hydroxide (Gel), Dried
|
|
613
|
RXNORM
|
IN
|
Aluminum Hydroxide Gel
|
|
46242
|
RXNORM
|
IN
|
aluminum magnesium hydroxide
|
|
615
|
RXNORM
|
IN
|
Aluminum Oxide
|
|
17618
|
RXNORM
|
IN
|
aluminum phosphate
|
|
54989
|
RXNORM
|
IN
|
aluminum potassium sulfate
|
|
543375
|
RXNORM
|
IN
|
Aluminum Sesquichlorohydrate
|
|
17621
|
RXNORM
|
IN
|
aluminum sulfate
|
As an implementer, an awareness of the nature of base ingredients
and there variations is useful as it can motivate you to look at the data in different
ways, both in terms of development and validation.
When is an Ingredient
not an Ingredient?
Every now and then you may encounter an ingredient that is
present in an ingredient set that is not an ingredient. You will recognize this because under certain
situations they will wreak havoc.
Sometimes it will be an inactive ingredient, as discussed earlier, and
other times it may be a clinical work-around.
An example could be an ingredient set that has ‘water’ and
an active ingredient. If the user
happens to select that drug (either by picking the ingredient set or the brand
name synonym) to represent an allergen, they have unwittingly indicated that
the patient is allergic to any ingredient set that includes ‘water’.
Another example of a clinical work-around is a ingredient
term that represents a concept like ‘sugar-free’, ‘alcohol-free’ or ‘Preservative-Free’. These were introduced to support firing significant
clinical alerts without requiring existing terminology users to re-program
their applications. In that respect they
are ingenious and likely saved patient’s lives.
The unintended consequence of this, like with the water example, is that
if a ingredient set with a ‘freeness’ ingredient is used as an allergen it
introduces the notion that the patient is allergic to everything else that is ‘sugar-free’. There are not many of these but if you
encounter one you should make sure that you have exceptions in your allergy
checking to ignore ‘free-ness’-based hits.
Finally, some ingredient terminologies may include the notion of a route of administration in an ingredient (see the above example of 'immune globulin' in RxNorm) this is less of an issue because the route is not typically represented as a distinct ingredient, so the net result is similar to a variation of a base ingredient. Sometimes in these cases the routed ingredient may be disconnected from the base ingredient for clinical reasons.
Ingredients Drive
Medication Terminologies
Every use model for medication terminologies is driven by
the ingredients. Take some time, with
whatever terminology you have chosen for your implementation, to understand how the ingredients work and
how they factor into the decision support modules. Understanding this facet of
you medication providers content will provide significant insight into how
everything else works.
In the next post of this series we will cover the secondary characteristics of a medication concept.
As we here at Clinical Architecture have been developing our Symedical product, I have had the pleasure of spending some quality time with UMLS Metathesaurus and RxNorm. As I was going through this journey of discovery, I thought to myself that it might be a good idea to share my findings and experiences with others who might also be looking into using RxNorm and UMLS to enhance or improve their clinical interoperability.
So, to that end, I have created the first of, in what I hope will be, a series of Screen Casts that provide some insight into UMLS and RxNorm.
(Video should work in all browsers but requires the Quicktime plug-in)
Basic Clinical Interoperability with RxNorm - Screencast
Special thanks Jan Willis and the other folks at NLM for their feedback.