Proposal for linking Dosage Forms to Routes of Administration

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This post is about basically the same problem outlined in this earlier discussion. Basically, when we have an OpenMRS Drug entry, it tells us the form that drug is in but not the valid ways that that drug can be administered. While we might need—in some cases—specific per-drug mappings, it’s also convenient for us to be able to express things like “you cannot order a capsule to be given intravenously”.

We had a start of a discussion around this on the O3 Squad call yesterday, which lead to a now very long Slack thread where we seem to be narrowing in on a way to represent this, so it’s time to bring this up for the broader community to discuss how we’re envisioning being able to support mapping from drug forms to a list of allowable routes, ideally without needing to add new metadata tables.

Our goal here is to leverage metadata that’s available in RxNorm that maps between drug forms, drug form groups, and valid routes of administration. This ends up looking something like this (I’ve stolen this from @akanter in the Slack thread):

Dose Form (examples) Dose Form Group (DFG) Derived Route(s) Notes
Tablet, Capsule, Solution Oral Product Oral Most reliable mapping
Chewable Tablet, Oral Suspension Oral Product Oral Pediatric variants
Sublingual Tablet Oral Product Sublingual Sometimes separated
Buccal Tablet/Film Oral Product Buccal Distinct mucosal route
Injection, Injectable Solution Injectable Product IV / IM / SC Ambiguous
Prefilled Syringe Injectable Product IV / IM / SC Context needed
Infusion Solution Injectable Product Intravenous More specific
Cream, Ointment, Gel Topical Product Topical Skin
Lotion, Foam Topical Product Topical Skin
Transdermal Patch Transdermal Product Transdermal Systemic absorption
Ophthalmic Solution Ophthalmic Product Ophthalmic Eye
Otic Solution Otic Product Otic Ear
Nasal Spray Nasal Product Intranasal
Inhaler, Nebulizer Solution Inhalant Product Inhalation Pulmonary
Rectal Suppository Rectal Product Rectal
Enema Rectal Product Rectal
Vaginal Cream, Tablet Vaginal Product Vaginal
Irrigation Solution Irrigation Product Irrigation Procedural use
Dialysis Solution Dialysis Product Intraperitoneal Specialized
Implant Implant Product Implantation Long-acting
Powder for Reconstitution (Injection) Injectable Product IV / IM / SC Still ambiguous
Oral Powder Oral Product Oral Depends on labeling

Basically this will allow us to take an existing CIEL concept like Tablet (CIEL:1513) and say this is an “Oral Product”, which means it can be given, e.g., “Orally”, “Sublingually” or “Buccally”.

Concretely, what we’ll be adding is:

  • A new concept class for drug routes and presumably dosage forms
  • Mappings in CIEL for the various Dosage Forms to appropriate Dosage Form Groups
  • The Dosage Form Groups and their mappings to the valid routes
  • An extension to the Drug REST API to facilitate retrieving the valid routes for a specific drug from those mappings

We will endeavor to ensure that future updates to the O3 UI (and the O2 UI) that may leverage this information fallback correctly (basically allowing all routes for cases where dosage form groups are missing or their mappings to valid routes are missing).

Thanks to @chibongho, @mogoodrich, @burke, and @akanter for the discussion around this. Please feel free to correct me if I’ve summarized any of this incorrectly or if my understanding here is wrong.

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Also flagging @mseaton for review

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Thanks so much for writing this all out, and generally sounds good, though interested in having others weigh in.

One point (which doesn’t affect the overall modelling, just the implemetnation),:

One thing to note is that although a Drug has a “Dosage Form” property, it appears that in the UI we generally don’t restrict the end users from changing that form when placing an order. If that’s intentional (or something we don’t want to change) then in the UI we need to base the “valid routes” on the “dosage form” the user actually selected, not the “Valid Routes” for the Drug (which would assumedly be based on “Dosage Form” for the drug)?

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We should probably fix the UI to enforce that. I think if we’re saying a specific drug has a dosage form (and it seems to be a required field) we should be treating the drug as restricted to that dosage form.

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That does seem right to me. Not sure of repercussions. @mseaton @fanderson @ddesimone thoughts? (Effectively, “Dose Unit” would become uneditable).

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Also, the example table needs to be expanded to include ALL reasonable routes of administration for a form group (as mentioned above, ORAL can mean any of the oral routes). I would also point out that these relationships are coming off the drug CONCEPT in the dictionary (which for CIEL are ingredients, multi-ingredients and some specific ingredients) and not the DRUG rows. I can’t remember whether O3 draws only from the DRUG table for those prescriptions/orders, or whether it uses concepts + metadata selections to generate a prescription where the dispensing module takes over and maps to drugs. If you are directly searching and selecting from the DRUG table, then we have another join back to concept to worry about.

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I’d think the most useful information for determining valid routes of administration for a drug form would be a many-to-many mapping from dose form to drug route. The dose form group might be informative, but creates ambiguity. For example, I would expect “sublingual” to be the only valid route and “oral” and “g-tube” to be invalid routes for a sublingual tablet; whereas, most immediate-release tablets or capsules have multiple valid routes (oral, g-tube, j-tube).

In any case, creating a getValidRoutes(Drug) method in the Drug API would allow us to encapsulate this business logic, create a decent 1.0 version for now, and then improve it over time.

Some additional, less common, routes to consider:

  • NG tube – nasogastric tube
  • G-tube - gastric tube
  • J-tube - jejunal (directly into small intestine) tube
  • Intratracheal – some drugs are given intratracheally in emergencies
  • Intra-arterial – sometimes chemotherapy or diagnostic meds are given directly into an artery
  • Epidural
  • Intraosseus – injected directly into marrow, typically an emergency situation
  • Intracardiac – rare
  • Intra-articular – treatments into joints
  • Intravitreal – injections directly into the eye