Ammonium Molybdate / Ammonium Tetrathiomolybdate
**Ammonium molybdate** and **ammonium tetrathiomolybdate (TTM)** are specialized antidotes primarily utilized in veterinary medicine for the investigational or compassionate treatment of **copper poisoning** in food animals, particularly sheep. > **Clinical Pearl:** Sheep are uniquely susceptible to copper accumulation and toxicity. These compounds are often used to rapidly bind and excrete excess systemic copper to prevent fatal hemolytic crisis and liver failure. * **Ammonium molybdate** is typically administered orally and is often combined with sulfates or thiosulfates. * **Ammonium tetrathiomolybdate (TTM)** is administered parenterally (IV or SC) but does not go into solution readily. * These compounds are often sourced from chemical supply houses as there are no veterinary-labeled products available.
Mechanism: Molybdate interacts with sulfur and copper in the gastrointestinal tract and systemic circulation to form **thiomolybdates**. * **In the GI tract:** Molybdate and sulfur combine to form thiomolybdates, which bind to dietary copper → forms insoluble copper-thiomolybdate complexes → prevents copper absorption and promotes excretion in feces. * **Systemically:** Parenteral TTM binds to free copper in the blood and extracts copper from metallothionein in the liver → forms a stable, inert complex → safely excreted by the kidneys.
Dosing by species
- Copper poisoning · 200 mg per head · PO · once daily · 3 weeks · Ammonium molybdate
- Copper poisoning · 1.7-3.4 mg per head · IV or SC · every other day · 3 treatments · Ammonium tetrathiomolybdate
- Copper poisoning · 100 mg with 1-gram sodium sulfate · PO · daily · Ammonium molybdate
- Copper poisoning · 200 mg ammonium or sodium molybdate plus 500 mg of sodium thiosulfate · PO · daily · up to 3 weeks
- Copper poisoning · 1.7 mg/kg IV or 3.4 mg/kg SC · IV/SC · every other day · 3 treatments · Ammonium tetrathiomolybdate
- Copper poisoning · 50-500 mg ammonium molybdate and 300-1000 mg sodium thiosulfate · PO · once daily · 3 weeks · Alternative to TTM
- Copper poisoning · 2-15 mg/kg · IV · q24h · 3-6 days · Ammonium tetrathiomolybdate
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Use with caution in pregnant animals (FDA Category C in humans)
Adverse effects
- Long-term toxic endocrinopathy (retention of TTM in CNS, pituitary, and adrenal glands)
- Infertility (delayed onset, 2-3 years post-treatment)
- Progressive unthriftiness and death (delayed onset)
Monitoring
- Clinical signs of copper toxicity (jaundice, hemoglobinuria, weakness)
- Liver and kidney function
- Long-term monitoring for unthriftiness or reproductive failure
Overdose
While acute overdose information is limited, long-term retention of ammonium tetrathiomolybdate (TTM) in the CNS, pituitary, and adrenal glands has been documented to cause a **toxic endocrinopathy**. This can result in delayed infertility, progressive unthriftiness, and death 2-3 years post-treatment.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.