# Oral iron preparations: gastrointestinal adverse events and medication adherence in female patients with iron deficiency anemia

## TL;DR

This study examines how gastrointestinal side effects from oral iron supplements affect medication adherence in women with iron deficiency anemia.

## Contribution

The study identifies factors influencing medication adherence in female IDA patients, finding gastrointestinal AEs are not the main barrier.

## Key findings

- Ferrous gluconate showed the strongest gastrointestinal AE signal, while ferrous fumarate showed the weakest.
- Medication adherence was influenced more by patient beliefs, doctor-patient relationship, and hemoglobin levels than gastrointestinal AEs.
- 64.86% of patients were adherent, while 35.14% were non-adherent.

## Abstract

The relationship between oral iron preparation-related gastrointestinal adverse events (AEs) and medication adherence in female patients with iron deficiency anemia (IDA) remains unclear.

To assess gastrointestinal AEs linked to oral iron preparations via the US FDA Adverse Event Reporting System (FAERS), evaluate medication adherence levels in female IDA patients, and analyze the impact of gastrointestinal AEs and other factors on their medication adherence.

Reporting odds ratio (ROR) and Proportional Reporting Ratio (PRR) were used to analyze oral iron preparation-related gastrointestinal AEs. The Medication Adherence Report Scale-5 (MARS-5) was used to assess patients’ medication adherence, while logistic regression analyzed the impact of factors (gastrointestinal AEs, medication beliefs, illness perception, doctor-patient relationship, social support) on medication adherence.

FAERS recorded 2,624 reports of gastrointestinal AEs following oral iron supplementation in female patients with IDA (January 2000–March 2025). Disproportionality analysis indicated that ferrous fumarate exhibited the weakest gastrointestinal AE disproportional reporting signal (ROR = 0.36, 95% CI 0.27–0.48; PRR = 0.44), with no positive signals detected, whereas ferrous gluconate displayed the strongest signal (ROR = 2.62, 95% CI 2.05–3.34; PRR = 1.90) and the most prominent positive signals. No significant gastrointestinal AE disproportional reporting signals were found for ferrous sulfate or iron polysaccharide complex. A cross-sectional study (148 patients) showed that adherent patients and non-adherent patients accounted for 64.86% and 35.14%, respectively. Multivariate logistic regression analysis indicated that gastrointestinal AEs were not significantly associated with medication adherence, while medication concern beliefs, doctor-patient relationship, and hemoglobin level were important factors affecting medication adherence in female IDA patients.

Gastrointestinal AEs are not a key factor affecting medication adherence. Reducing patients’ medication concerns, improving the doctor-patient relationship and reinforcing counseling to avoid premature medication withdrawal due to elevated hemoglobin levels are beneficial to enhancing medication adherence in female IDA patients.