Pharmacokinetics of ammonium tetrathiomolybdate following intravenous administration in sheep

South African Mutton Merino wethers (n = 5) were each dosed with 2.5 g copper oxide needles. Three weeks later the sheep were placed on stainless steel metabolic crates to facilitate urine and faecal collection. Ammonium tetrathiomolybdate (TTM) (1.7 mg kg-1) was administered intravenously, blood samples were collected at intervals and different pharmacokinetic parameters for TTM were determined and are presented. Serum molybdenum concentration data were best described by a 2-compartmental open model with first order rate constants. An elimination half-life (T1/2 beta) of 396.8 min, steady state volume of distribution (Vdss) of 0.8 e kg-1 and total body clearance (C1B) of 1.53 ml kg-1 min-1 were observed using non-linear compartmental analysis. A significant (p < or = 0.05) increase in molybdenum excretion in the faeces occurred at 24 and 48 h following TTM administration. No increase in faecal and urinary copper excretion could be demonstrated, probably because the sheep were not copper-loaded. However, before a shorter dosage interval can be recommended for the treatment of sheep during the haemolytic crisis of chronic copper poisoning, further research in copper-loaded sheep is indicated.