# Safety of individualized herbal medicine for dysmenorrhea: pharmacovigilance from South Korea’s national pilot

## TL;DR

This study found that reimbursed individualized herbal medicine for dysmenorrhea in South Korea is safe and did not increase serious adverse events.

## Contribution

The study introduces a claims-based pharmacovigilance approach for monitoring herbal medicine safety using national health data.

## Key findings

- Reimbursed HMDs were not linked to increased risk of severe adverse events.
- Safety patterns remained consistent across all time points and sensitivity analyses.
- The study provides a scalable template for pharmacovigilance using standardized endpoints.

## Abstract

In 2020, South Korea’s National Health Insurance (NHI) began reimbursing individually prescribed herbal medicine decoctions (HMDs) for dysmenorrhea, highlighting the need for robust post-coverage safety monitoring using national claims data.

To evaluate the safety of reimbursed HMDs for dysmenorrhea and demonstrate a claims-based pharmacovigilance approach to inform benefit management and clinical guideline integration.

A retrospective cohort study was conducted using the Health Insurance Review & Assessment (HIRA) national claims database from 2015 to 2022. HMD users were coarsened-exact-matched to nonusers on sociodemographic and clinical characteristics. Difference-in-differences models compared pre- and post-coverage outcomes at 1, 3, 6, and 11 months. Primary outcomes were hepatotoxicity and renal failure; secondary outcomes included allergic reactions, emergency department visits and hospitalizations.

The matched cohort comprised 8,989 HMD users and 8,989 nonusers. Reimbursed HMDs were not associated with increased risk of severe adverse events at any time point. At 3 months, DID estimates were −2.6 (95% CI −411.8, 406.6) for hepatotoxicity and −7.2 (95% CI −402.3, 388.0) for renal failure, with consistent safety patterns across endpoints and sensitivity analyses.

Coverage of individually prescribed HMDs under South Korea’s NHI system was not associated with elevated serious safety risks for dysmenorrhea. These findings support continued reimbursement and provide a scalable template for claims-based pharmacovigilance using standardized endpoints, routine signal detection, and feedback to benefit design and clinical practice.