Dimercaprol
Dimercaprol (also known as **British Anti-Lewisite** or **BAL**) is a heavy metal chelating agent primarily used in veterinary medicine to treat **arsenic** toxicity. It is also occasionally utilized for lead, mercury, and gold intoxications. Originally developed during World War II as an antidote for Lewisite (an arsenic-based chemical warfare agent), it contains sulfhydryl groups that bind to heavy metals, preventing them from interfering with essential cellular enzymes. > **Clinical Pearl:** Dimercaprol is formulated in peanut oil and must be given via deep intramuscular injection, which can be quite painful. It is relatively ineffective for certain metals like selenium and is strictly contraindicated in iron, cadmium, and selenium poisoning because the resulting dimercaprol-metal complex is more toxic than the metal alone.
Mecanismo: Heavy metals exert their toxic effects by binding to **sulfhydryl (-SH) groups** on essential cellular enzymes, leading to enzyme inactivation. Dimercaprol contains two sulfhydryl groups that act as "decoys." * **Dimercaprol + Heavy Metal → Heterocyclic Ring Complex** * This complex is more stable than the metal-enzyme bond, allowing the metal to be pulled away from the tissues and excreted via the kidneys and feces. > **Mechanistic Note:** The chelation is not irreversible. The complex can dissociate as dimercaprol concentrations decrease, if oxidized, or in an acidic environment. Therefore, **alkalinizing the urine** is crucial to prevent the complex from dissociating in the kidneys and causing nephrotoxicity.
Dosificación por especie
- Arsenic toxicity · 2.5-5 mg/kg IM · IM · q4h for first 2 days; q8h on 3rd day; BID for next 10 days · Until recovery · Intensive supportive care required. 5 mg/kg dose only for acute cases and only for the first day. Give with sodium thiosulfate.
- Arsenic toxicity · 2.5-5 mg/kg IM · IM · q4h for first 2 days, then q12h · Until recovery · If ingestion was within 36 hours. Use emetics/gastric lavage if recent. Institute fluid therapy.
- Arsenic toxicity · 4 mg/kg IM · IM · q4-6h · Max 4 continuous days · Do not give for more than 4 continuous days.
- Arsenic toxicity · 5 mg/kg IM loading dose, then 2.5 mg/kg IM · IM · q3-4h for two days, then progressively lengthen to q12h · Until recovery · Loading dose of 5 mg/kg for acute cases only.
- Arsenic toxicity (no clinical signs) · 3 mg/kg IM · IM · q8h
- Arsenic toxicity (clinical signs) · 6 mg/kg IM · IM · q8h · 3-5 days
- Arsenic, lead or mercury poisoning · 2.5-5 mg/kg IM · IM · q4h · 2 days · Efficacy questionable unless given before signs appear or very early. Withdrawal info not available.
- Mercury toxicity · 3 mg/kg IM · IM · four times daily for 3 days, then twice daily · 13 days total · Treatment is often unsuccessful.
Vías de administración
Contraindicaciones
- Impaired hepatic function (unless secondary to acute arsenic toxicity)
- Iron poisoning
- Cadmium poisoning
- Selenium poisoning
Efectos adversos
- Pain at injection site
- Vomiting
- Seizures (at higher dosages)
- Transient increases in blood pressure
- Tachycardia
- Nephrotoxicity
Interacciones farmacológicas
- Iron · Forms a highly toxic complex. Do not administer with iron salts; wait at least 24 hours after the last dimercaprol dose before starting iron therapy.
- Selenium · Forms a highly toxic complex. Do not administer with selenium salts; wait at least 24 hours after the last dimercaprol dose before starting selenium therapy. · major
- Cadmium · Forms a highly toxic complex. · major
- Uranium · Forms a highly toxic complex.
- Iron supplements · Forms highly toxic complexes · major
Monitorización
- Liver function
- Renal function
- Hemogram
- Hydration and perfusion status
- Electrolytes and acid/base status
- Urinary pH (maintain alkaline pH)
Sobredosis
Clinical signs of dimercaprol overdosage in animals include **vomiting, seizures, tremors, coma, and death**. No specific doses were located to correspond with these clinical signs. Treatment should be supportive and symptomatic.
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