Famphur persistence

Famphur residues of 1 to 3 mg/kg fresh weight (FW) are common in cattle tissues after normal pour-on applications of the chemical (Annand et al. 1976). The half-time persistence of famphur in subcutaneous fat of cattle after a single pour-on application was 0.9 days and was independent of dose within the range of 25 to 150 mg/kg BW or initial tissue residues between 1.8 and 12.3 mg/kg FW fat residues were <0.08 mg/kg FW 5 days after treatment and <0.01 mg/kg FW after 11 days. These observations suggest that famphur tissue residues are near or below detection levels within 1 week after treatment, even with gross misuse of the chemical (Annand et al. 1976). However, because famphur persists on cattle hair for >90 days at concentrations >1000 mg/kg, this has serious implications for local populations of birds (Henny et al. 1985). 

These observations suggest that famphur tissue residues are near or below detection levels within 1 week after treatment, even with gross misuse of the chemical. However, because famphur persists on cattle hair for >90 days at concentrations of > 1000.0 mg/kg, this has serious implications on the local populations of birds. 

Famphur is administered to livestock by intramuscular or subcutaneous injection, through the diet, as a dermal pour-on, or as an oral bolus. In mammals, famphur induced mortality at concentrations as low as 11.6 mg/kg BW in intraperitoneal injection (mouse), 27 mg/kg BW in a single oral exposure (mouse), >33.3 mg/kg BW in an intramuscular injection (Brahman cattle, Bos indicus), and 400 mg/kg BW in a dermal application (rat, Rattus sp.). Latent effects of famphur exposure were reported in reindeer (Rangifer tarandus) hinds 1 year posttreatment (altered blood chemistry). Famphur is rapidly metabolized by mammals. The half-time persistence of famphur and famoxon in subcutaneous fat of cattle after a single pour-on application is 0.9 days and is independent of dose between 25 and 150 mg/kg BW or initial tissue residues between 1.8 and 2.3 mg/kg BW. 

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