# Accidental tamoxifen ingestion in a two-year-old child without major immediate symptoms: Case report

## TL;DR

A 2-year-old child accidentally ingested tamoxifen, a breast cancer drug, but showed no immediate serious symptoms, though long-term monitoring is recommended.

## Contribution

This case report documents a rare incident of accidental tamoxifen ingestion in a toddler and provides pharmacokinetic data from the event.

## Key findings

- The child ingested an estimated 31–37 mg of tamoxifen without experiencing acute adverse effects.
- Tamoxifen plasma levels peaked at 53.8 ng/mL two hours post-ingestion, but endoxifen levels were subtherapeutic.
- Long-term follow-up is advised due to tamoxifen's anti-oestrogen properties and potential developmental risks.

## Abstract

Tamoxifen is a selective oestrogen receptor modulator indicated for the treatment of breast cancer in adults. The recommended dose is 20 mg orally once daily. We report an accidental tamoxifen ingestion in a 2-year-old female who accessed the tamoxifen from a pill bottle stored in a bag while unsupervised. Activated charcoal and sodium sulphate were administered approximately 2.5 h after ingestion. Plasma concentrations of both tamoxifen and active metabolite endoxifen were determined. The maximum plasma concentration of tamoxifen was 53.8 ng/mL, occurring two hours after ingestion. In contrast, the plasma concentration of endoxifen measured at 22 h after ingestion was 0.771 ng/L, which is considered subtherapeutic in adults. However, given the prolonged half-life of endoxifen, the plasma levels may still be rising at this point. The ingested dose was estimated to be around 31–37 mg, based on the plasma levels of tamoxifen and endoxifen. The actual ingested amount may have been higher due to early oral administration of activated charcoal. No direct serious events occurred during a hospital admission of 31 h. Given the anti-oestrogen properties of tamoxifen and the critical role of oestrogen in pubertal development long-term follow-up is recommended to monitor potential delayed effects.

•A 2-year-old ingested approximately 31–37 mg tamoxifen unsupervised.•Plasma concentrations are measured to follow the course of the patient.•No acute adverse events occurred, but long-term monitoring is advised for developmental effects.

A 2-year-old ingested approximately 31–37 mg tamoxifen unsupervised.

Plasma concentrations are measured to follow the course of the patient.

No acute adverse events occurred, but long-term monitoring is advised for developmental effects.