Intravenous administration of thiomolybdate for the prevention and treatment of chronic copper poisoning in sheep.

1. Twenty-six sheep were used in experiments designed to test the effectiveness of ammonium tetrathiomolybdate in the prevention and treatment of chronic copper poisoning. 2. Intravenous injections of 100 mg ammonium tetrathiomolybdate twice weekly (a) prevented the occurrence of haemolytic crisis in sheep repeatedly dosed with copper sulphate and (b) minimized tissue damage and prevented further haemolytic crisis when given to sheep already in haemolysis. 3. Thiomolybdate prevented excessive deposition of Cu in the liver of sheep receiving orally large amounts of Cu and decreased liver Cu levels in sheep that were not given additional Cu. In the latter sheep, 50 mg ammonium tetrathiomolybdate given twice weekly did not produce histologically-detectable tissue damage even though liver and kidneys contained high levels of molybdenum, and kidneys contained elevated levels of Cu. 4. It is concluded that chronic Cu poisoning can be successfully prevented or treated by intravenous injection of appropriate doses of ammonium tetrathiomolybdate.