# Dimercaprol (BAL): veterinary dose and monograph

> Dimercaprol (BAL) is a veterinary drug. A dithiol HEAVY-METAL CHELATOR — the classic antidote for ARSENIC, inorganic MERCURY and GOLD poisoning, and used WITH calcium-EDTA for LEAD poisoning (dimercaprol enters cells/CNS and mobilises lead so EDTA can excrete it, reducing the… Indications include arsenic poisoning (the classic indication); inorganic mercury and gold toxicosis; lead poisoning — IN COMBINATION with calcium-EDTA (especially with CNS signs). This monograph lists 4 reference doses for dogs, cats, cattle and horses, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/dimercaprol · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** BAL, British Anti-Lewisite, Dimercaprol in oil
- **Species with doses:** Dogs, Cats, Cattle and Horses
- **General dose range:** 2.5–5 mg/kg IM q4h tapering (per protocol) — check the species tables for the indication
- **Routes:** IM
- **Last reviewed:** 1 October 2026

## Indications

- Arsenic poisoning (the classic indication)
- Inorganic mercury and gold toxicosis
- Lead poisoning — IN COMBINATION with calcium-EDTA (especially with CNS signs)

## Dimercaprol (BAL) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Dimercaprol (BAL) doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Arsenic / mercury / (lead with EDTA) | 2.5–5 mg/kg | IM | q4h for 2 days, q8h on day 3, then q12h until recovery | — |

- Arsenic / mercury / (lead with EDTA): Plumb’s p.411: 2.5–5 mg/kg deep IM (5 mg/kg only on day 1 of acute cases) q4h for 2 days, q8h on day 3, then twice daily up to 10 days, with sodium thiosulfate 40–50 mg/kg IV (Neiger); 4 mg/kg IM q4–6h for no more than 4 days (Grauer & Hjelle). Papich 5e: 4 mg/kg IM q4h. Deep IM in oil only — never IV. Keep well hydrated.

### Cats

*Dimercaprol (BAL) doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Arsenic poisoning | 2.5–5 mg/kg | IM | q4h then taper | — |

- Arsenic poisoning: Plumb’s p.411 (Reid & Oehme): 2.5–5 mg/kg IM q4h for the first 2 days, then q12h until recovery, with fluid therapy; start if ingestion was within 36 h. Papich 5e: 4 mg/kg IM q4h. For lead, succimer or Ca-EDTA are preferred. Monitor renal function.

### Cattle

*Dimercaprol (BAL) doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Arsenic poisoning | 2.5–6 mg/kg | IM | q4–8h | — | Withdrawal NOT established — treat as extra-label |

- Arsenic poisoning: Plumb’s p.411: ruminants 2.5–5 mg/kg IM q4h for 2 days (Osweiler); arsenic — 3 mg/kg IM q8h if no signs, 6 mg/kg IM q8h for 3–5 days with signs (Post & Keller); mercury 3 mg/kg IM four times daily for 3 days then twice daily for 10 days. Papich 5e: 4 mg/kg IM q4h. No food-animal withdrawal available — obtain FARAD advice. Efficacy is doubtful unless given early.

### Horses

*Dimercaprol (BAL) doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Arsenic poisoning | 1–5 mg/kg | IM | 5 mg/kg once, then 3 mg/kg q6h (day 1), then 1 mg/kg q6h for ≥2 days | — |

- Arsenic poisoning: Plumb’s p.411 (Oehme; Rees): 5 mg/kg IM initially, 3 mg/kg IM q6h for the rest of day 1, then 1 mg/kg IM q6h for 2 or more days; only effective within hours of ingestion. Also sodium thiosulfate 50–75 g PO q6–8h. Papich 5e: 4 mg/kg IM q4h. Painful IM.

### Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

*Dimercaprol (BAL) doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Arsenic poisoning | 2.5–6 mg/kg | IM | q4–8h | — | Withdrawal NOT established — treat as extra-label |

- Arsenic poisoning: Plumb’s p.411: ruminants 2.5–5 mg/kg IM q4h for 2 days (Osweiler); arsenic — 3 mg/kg IM q8h if no signs, 6 mg/kg IM q8h for 3–5 days with signs (Post & Keller); mercury 3 mg/kg IM four times daily for 3 days then twice daily for 10 days. Papich 5e: 4 mg/kg IM q4h. No food-animal withdrawal available — obtain FARAD advice. Efficacy is doubtful unless given early.

## Contraindications

IRON, CADMIUM or SELENIUM poisoning (the dimercaprol-metal complex is MORE toxic — contraindicated). Significant hepatic impairment (relative; it is hepatically processed). Peanut/oil-vehicle allergy (formulated in peanut oil). G6PD-type oxidative susceptibility (haemolysis). Renal failure with anuria (chelate not excreted). Known hypersensitivity.

## Species-specific warnings

> **Caution:** Cats: Cats are prone to oxidative haemolysis — monitor PCV; dose carefully and maintain hydration.

## Adverse effects

- Pain/sterile abscess at the IM injection site (oil vehicle)
- Hypertension and tachycardia, vomiting, hypersalivation, restlessness (dose-related)
- Nephrotoxicity (the chelate is nephrotoxic — maintain urine flow/alkalinise)
- Haemolysis (oxidative); fever

## Drug interactions

- Iron / cadmium / selenium: form MORE toxic complexes — contraindicated; do not give iron supplements concurrently
- Calcium-EDTA: complementary (combined for lead poisoning)
- Alkaline urine: stabilises the chelate and protects the kidney

## Pregnancy and lactation

Reserve for serious heavy-metal poisoning where maternal benefit outweighs risk; limited data.

## Monitoring

- Renal function (BUN/creatinine, urine output) and hydration — nephrotoxic chelate
- Blood metal levels / clinical response
- PCV (haemolysis), blood pressure, injection sites
- Urine pH (keep alkaline) 

## Toxicity and overdose

Dose-related toxicity includes hypertension/tachycardia, vomiting/hypersalivation, fever, injection-site pain/abscess, oxidative haemolysis, and NEPHROTOXICITY (the chelate damages the kidney, especially in acidic urine/dehydration). The dangerous error is using it for iron/cadmium/selenium, where the complex is more toxic than the metal alone.

Management: No specific antidote. Discontinue; supportive care — maintain hydration and urine output, alkalinise urine to protect the kidney and stabilise the chelate, manage hypertension/tachycardia, and monitor renal function and PCV (haemolysis). Antihistamine/antipyretic for febrile reactions.

## Clinical pearls

- The antidote for ARSENIC and inorganic MERCURY — and the intracellular/CNS partner for calcium-EDTA in LEAD poisoning (it mobilises brain lead so EDTA can excrete it)
- Deep, PAINFUL IM in oil only — never IV; keep the patient hydrated and the urine alkaline to protect the kidney
- NEVER use for iron, cadmium or selenium poisoning — the chelate is more toxic than the metal
- For stable lead poisoning, oral succimer (DMSA) has largely replaced the EDTA/BAL combination

## Mechanism of action

Dimercaprol has two free sulphydryl (thiol) groups that bind heavy-metal ions (arsenic, mercury, gold, lead), forming a stable, water-soluble metal-dithiol chelate that is excreted in the urine — protecting essential sulphydryl-containing enzymes the metals would otherwise inactivate. Being lipophilic, it distributes into cells and the CNS (useful for mobilising intracellular/brain lead), which is why it is paired with calcium-EDTA for lead to avoid redistributing mobilised lead to the brain.

## Formulations and products

- Injection 50 / 100 mg/mL in oil (deep IM only)
- Dimercaprol (BAL in Oil) — 50 / 100 mg/mL in oil, IM injection (in oil) (human-label)

## Storage

Ampoules (in oil): 15–30 °C, protect from light; do not freeze. For deep IM use only.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Dimercaprol (BAL) for dogs?

Reference doses for Dimercaprol (BAL) in dogs: 2.5–5 mg/kg IM q4h for 2 days, q8h on day 3, then q12h until recovery (Arsenic / mercury / (lead with EDTA)). Confirm against the label and the patient before use.

### What is the dose of Dimercaprol (BAL) for cats?

Reference doses for Dimercaprol (BAL) in cats: 2.5–5 mg/kg IM q4h then taper (Arsenic poisoning). Confirm against the label and the patient before use.

### What is the dose of Dimercaprol (BAL) for cattle?

Reference doses for Dimercaprol (BAL) in cattle: 2.5–6 mg/kg IM q4–8h (Arsenic poisoning). Confirm against the label and the patient before use.

### What is the withdrawal period for Dimercaprol (BAL)?

Cattle, IM (Arsenic poisoning): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Dimercaprol (BAL) not be used?

IRON, CADMIUM or SELENIUM poisoning (the dimercaprol-metal complex is MORE toxic — contraindicated). Significant hepatic impairment (relative; it is hepatically processed). Peanut/oil-vehicle allergy (formulated in peanut oil). G6PD-type oxidative susceptibility (haemolysis). Renal failure with anuria (chelate not excreted). Known hypersensitivity.

### What are the side effects of Dimercaprol (BAL) in animals?

Pain/sterile abscess at the IM injection site (oil vehicle); Hypertension and tachycardia, vomiting, hypersalivation, restlessness (dose-related); Nephrotoxicity (the chelate is nephrotoxic — maintain urine flow/alkalinise); Haemolysis (oxidative); fever.

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.