Handling medications
This section aims to clarify how medications information will be articulated in this specification, and what data to expect from the pharmacy systems.
Structured dosage vs free text
For provider systems that support fully structured dosage instructions a complete Dosage structure SHOULD be populated as per implementation guidance.
- Where fully structured dosage instructions are not supported by provider systems
Dosage.textandDosage.patientInstructionMUST be populated as described below. - All other elements that are part of the dosage datatype are optional, and MAY be populated in line with ISN DAPB4013.
A separate guide covering structured dosage in great detail has been created by NHS England. The guidance is scoped for FHIR R4 dosage element; however, other than a slight change in element names, it still applies for FHIR STU3.
Usage of VMP, AMP and AMPP
While interoperability between care settings is desirable and, in particular, the representation of medications regardless of how they have been prescribed, the scope of this specification is for primary care and dispense events that have occurred within a community pharmacy.
Usage of dm+d
You must be familiar with the NHS dictionary of medicines and devices (dm+d) and SNOMED-CT.
The dm+d is the NHS choice for recording details of medicines and devices in the electronic patient record and is the medicines standard approved by the Standardisation Committee for Care Information (SCCI) as an NHS Fundamental standard.
All dm+d concepts are included in the SNOMED-CT UK Drug Extension and all dm+d codes are SNOMED-CT codes. The basic dm+d structure with the associated SNOMED CT UK drug extension Trade Family concept class is shown below, with examples at each level.
As such, please ensure that a dm+d code as a medicationCodeableConcept is used where possible with the code system: https://dmd.nhs.uk, over a medicationReference.
Product vs dose-based prescribing
You must be familiar with how prescribing processes are sometimes different between primary and secondary care settings and should read the detailed dm+d implementation guidance for each care setting published on the NHSBSA website.
All prescribing in primary care, the majority of which is performed within general practice, is using product-based prescriptions. The prescriber chooses a product, which in the dm+d model would be a Virtual Medicinal Product (VMP) or if a specific branded product is required, an Actual Medicinal Product (AMP). A VMP is a pre-coordinated SNOMED concept that defines the medication, strength, form, and possibly unit of presentation. An AMP additionally defines the supplier and a brand name where applicable.
Primary care prescribing uses VMP and AMP concepts because dispensing is performed, in the majority of cases, in community pharmacies for self-administration by the patient. It would not be efficient or appropriate for a pharmacist to discuss with the patient specifics of which drug dose form they would prefer.
Primary care therefore deals with products where a prescription comprises of a VMP or AMP, a quantity of that product, and a dosage instruction.
Secondary care prescribing prefers to use the less specific Virtual Therapeutic Moiety (VTM) concept plus a dosage instruction, creating a dose-based prescription (more commonly known as an 'order' in secondary care). The combination of a VTM plus a dosage instruction gives ward clinicians the flexibility to use different formulations of medicine depending on the needs of the patient. For example, if the patient is having difficulty swallowing then the medication in a liquid form may be easier to take than a tablet form. The prescription order is typically as generic as is safely possible. In some cases, it may just be a VTM plus a dose quantity, route and frequency - for example, 'Ibuprofen 400mg, oral, three times daily'.
Both care settings would benefit from having a structured way to record dosage instructions, but it becomes essential when medicines information is shared between care settings to reduce the need for human intervention and improve patient safety. Examples of this are the identification of current medication on hospital admission or to share changes in on-going medication back to the patient's GP following hospital discharge.
Today, without an implemented dose structure, clinicians in both care settings need to convert between product-based and dose-based instructions. The few occasions when human error occurs during this conversion process can lead to significant patient harm. It is here that clinical software systems which understand structured dosage instructions can support the clinician. A dose-based instruction can be mapped to VMPs or AMPs for pharmacy stock picking lists or repeat prescribing by general practice. A product-based repeat prescription can be converted into a dose-based instruction for continued medicines administration while the patient is in hospital care.
Additionally, the growing demand for patient-facing applications to support medicines compliance can benefit from having structured dosage instructions as these can be used to trigger alerts and notifications to patients when it is time to take or reorder medication. It would also be possible for devices and machines that perform medicines administration, for example, hospital infusion machines, to be automatically set up to deliver the rate of medicine required or alert the clinician if incorrectly user-programmed (for example, too fast or too slow).
NHS dm+d concepts and impact on use of the FHIR dosage element
All references to medication must use the NHS standard of dm+d. The dm+d concept class used will give different levels of specificity, as required by the prescriber.
The most generic medication instruction would specify a dm+d Virtual Therapeutic Moiety (VTM) plus a dosage instruction.
The most specific medication instruction, for the purposes of prescribing, would specify a dm+d Actual Medicinal Product (AMP) plus a dosage instruction.