[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Chelating agents](https://durgical.com/en/pharmacology/classes/chelating-agents/) › Unithiol

# Unithiol

## Chelating agents?

Chelating agents

A water-soluble dithiol chelator (DMPS) used for arsenic and mercury poisoning; a less toxic relative of dimercaprol.

Updated Nov 12, 2026

Also called: DMPS, sodium 2,3-dimercaptopropane-1-sulfonate

## Quick facts

**Group**
[Chelating agents](https://durgical.com/en/pharmacology/classes/chelating-agents/)

**Target**
Arsenic and mercury ions in blood and tissues

**Used for**
Severe acute arsenic poisoning · Mercury poisoning

**Key effects**
Loss of zinc and copper

**Monitor**
Urine metal levels to judge response · Kidney function

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

Unithiol carries two neighbouring thiol (-SH) groups, the same metal-gripping design as dimercaprol, plus a charged sulfonate group that makes it water-soluble. The thiols bind arsenic and mercury more tightly than the sulfhydryl groups of the body's enzymes, forming a stable complex that the kidneys excrete. Being water-soluble, it is less toxic than dimercaprol and can be given intravenously or by mouth. Chelation helps most when it starts within hours of absorption.

- Arsenic or mercury binds and blocks thiol enzymes
- Unithiol's two thiols grip the metal more tightly
- A water-soluble complex forms
- The kidneys excrete the metal

## Indications

- Severe acute arsenic poisoning, under the guidance of a toxicology expert [Arsenic poisoning →](https://durgical.com/en/conditions/arsenic-poisoning/)
- Mercury poisoning [Mercury poisoning →](https://durgical.com/en/conditions/mercury-poisoning/)

## Adverse effects

- Loss of zinc and copper, which it also binds

## Contraindications

- Known allergy to unithiol
- Not used to reverse established arsenic neuropathy, which chelation does not improve

## Key interactions

**Dimercaprol (BAL)**
Unithiol is its water-soluble, less toxic relative and has largely replaced it for arsenic

## What is monitored

- Urine metal levels to judge response and the end of treatment
- Kidney function, since the complex leaves through the kidneys
- Zinc and copper status during longer courses

## Administration and safety

- Used only after a poison centre or clinical toxicologist has been consulted
- Often obtained through special-access programmes, so hospitals plan their supply
- Started as early as possible after acute exposure, when chelation helps most

## Pregnancy and breastfeeding

Information on use in pregnancy is very limited; in serious poisoning the decision rests with toxicology specialists.

## Nursing care

- Take a clear exposure history: which metal, how, and when
- Collect urine samples as instructed, ideally before chelation starts
- Watch fluid balance and urine output
- Remove the patient from the source of exposure; chelation does not replace this

## Pharmacokinetics

**Absorption**
Given intravenously in acute poisoning; also absorbed by mouth

**Elimination**
Mainly by the kidneys, together with the bound metal

## Memory aid

UNI-THIOL: two thiols, one goal, and the S in DMPS stands for the sulfonate that lets it dissolve and leave in urine.

## Test yourself

Think of the answer, then tap the question to see it.

## Which two metals is unithiol mainly used for?

Arsenic and mercury.

## What makes unithiol less toxic than dimercaprol?

Its sulfonate group makes it water-soluble, so it stays in body water and leaves through the kidneys.

## Why does early treatment matter in acute arsenic poisoning?

Chelation helps most within hours of absorption; its benefit falls as time passes.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/unithiol/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 3

- [Dimercaprol](https://durgical.com/en/pharmacology/dimercaprol/)
- [Succimer](https://durgical.com/en/pharmacology/succimer/)
- [Penicillamine](https://durgical.com/en/pharmacology/penicillamine/)

## Related conditions 2

- [Arsenic poisoning](https://durgical.com/en/conditions/arsenic-poisoning/)
- [Mercury poisoning](https://durgical.com/en/conditions/mercury-poisoning/)

[← Back to the class: Chelating agents](https://durgical.com/en/pharmacology/classes/chelating-agents/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Arsenic Toxicity: How Should Patients Overexposed to Arsenic Be Treated and Managed? | Environmental Medicine | ATSDR](https://archive.cdc.gov/www_atsdr_cdc_gov/csem/arsenic/patient_exposed.html) (Agency for Toxic Substances and Disease Registry (CDC), 2026); [Chelating agents (excluding Deferoxamine)](https://www.ciusss-capitalenationale.gouv.qc.ca/en/antidotes/chelating-agents-excluding-deferoxamine) (Santé Québec Capitale-Nationale (Canadian antidote guide), 2022).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/pharmacology/unithiol/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/unithiol/