Context

This codelist aims to: - Identify all medications prescribed to treat epilepsy. - Exclude medications prescribed for other conditions.

These codelists are an update of the 2018 SNOMED codelists published by Tsang et al., 2023. We created updated codes for our analysis to capture new prescriptions or codes that were changed since 2018. We chose codes the BNF system, because they are more intuitive to develop and easier to update in the future.

Search terms / synonyms / search strategy

-The anti-epileptic medication codelist from Tsang et al., 2023 were converted into BNF -A list of the relevant BNF chapters, sections, and paragraphs were obtained from the converted 2023 codelist (e.g. the chapter: Central nervous system; section: anti-epileptic drugs, etc) -Medicines were matched based on their names and BNF chapter/section/paragraph -Using the relevant BNF chapter/section/paragraph, additional medicines listed in the 2025 BNF, but not present in the 2023 codes, were identified. These were verified using an online search, and a review of primary care prescribing data on OpenPrescribing -Some medications in the 2023 list were removed if they were not indicated for the condition. These were verified with an online search.

Inclusion/exclusion criteria

Inclusion criteria: - Medications were included if they are prescribed in primary care for epilepsy.

Exclusion criteria -Codes were excluded if the BNF section indicated the code referred to the medication as prescribed for psychosis & related disorders (and the medication was already captured under an epilepsy-specific code). - Codes for gabapentin sold as a topical gel or cream that were under the BNF section for neuropathic pain, were also excluded.

Borderline cases

The below medications were ultimately included in the codelist, even if they are also indicated for other conditions. In the CMS, individuals are identified as having epilepsy only if they have a clinical code AND a prescription code for epilepsy - therefore, felt it was reasonable to include these medications.
-Gabapentin/pregabalin - used mostly for neuropathic pain -Carbamazepine - also used for trigeminal neuralgia -Sodium valproate/valproic acid - also used for bipolar disorder -Lamotrigine - also used for bipolar disorder -Primidone - also used for essential tremor

Additional information

See for more detail on codelist development: https://github.com/opensafely/codelist-development/issues/384 Codelist underwent pharmacist and clinical review by Chris Wood and Dr. Michael Marks.