---
title: "Prussian blue is the FDA-approved oral antidote for radioactive cesium and thallium poisoning"
type: "claim"
status: "seedling"
source_url: "https://remm.hhs.gov/prussianblue.htm"
source_title: "Prussian Blue - Radiation Emergency Medical Management"
source_author: "U.S. Dept. of Health and Human Services, Radiation Emergency Medical Management (REMM)"
source_date: "2026-07-09T00:00:00.000Z"
source_quote: "This oral ion-exchange drug is indicated for decorporation of cesium and thallium and has been shown to be highly effective for Cs-137 contamination."
source_tier: 1
audit_status: "capture-verified"
writer_model: "claude-opus-4-8"
provenance: "Promotion from 10-inbox/raw/2026-07-09-hop-prussian-blue-radiological-antidote.md, 2026-07-11"
origin: "batch"
derived_from: "10-inbox/raw/2026-07-09-hop-prussian-blue-radiological-antidote.md"
date_created: "2026-07-11T00:00:00.000Z"
tags: ["toxicology","radiological-medicine","radionuclides","pigments","cross-domain-bridge","hop"]
drafted_in: ["2026-07-13-made-to-leave","made-to-leave"]
---


Insoluble Prussian blue — the ferric hexacyanoferrate pigment [[claim-prussian-blue-accidentally-discovered-1706-as-failed-red-pigment|discovered by accident in 1706]] — is a modern pharmaceutical. Marketed as Radiogardase, it is approved by the U.S. Food and Drug Administration as an oral drug for people internally contaminated with radioactive cesium or with thallium. The U.S. HHS Radiation Emergency Medical Management resource describes it as an "oral ion-exchange drug ... indicated for decorporation of cesium and thallium" that "has been shown to be highly effective for Cs-137 contamination."

The general mechanism is decorporation by sequestration in the gut: swallowed Prussian blue is not appreciably absorbed, and its porous crystal lattice binds cesium and thallium ions that enter the intestine — both those swallowed and those re-secreted from the bloodstream into the gut via enterohepatic and enterosystemic recirculation — so the bound ions leave in the stool instead of being reabsorbed. This interrupts the recirculation that would otherwise keep the isotopes in the body, reducing their biological half-life. The precise physical chemistry of *why* the lattice selectively traps monovalent Cs⁺/Tl⁺ over other cations, and the quantitative half-life reductions sometimes cited, rest on primary papers not yet sourced in this vault; that verification is tracked in [[question-verify-prussian-blue-cesium-selectivity-mechanism-primary]].

This is a genuine cross-domain bridge: an 18th-century failed dye is 21st-century standard-of-care for nuclear contamination. The claim connects the vault's pigment/color-chemistry material to its nuclear-radionuclide cluster — most directly [[claim-burevestnik-reactor-emits-radionuclides-in-exhaust]], where a nuclear-powered cruise missile is modeled as emitting cesium-adjacent gaseous radionuclides. Prussian blue was deployed at scale in [[claim-prussian-blue-was-deployed-at-scale-in-the-1987-goiania-cesium-137-accident|the 1987 Goiânia cesium-137 accident]].