Organophosphorus veterinary

Organophosphorus Veterinary Medicines Table 10.5 Some ectoparasites of sheep. 

Although several chemicals, e.g. arsenicals and organophosphorus compounds, had been used with some effect to treat specific helminth infections, the introduction in 1930 of phenothiazine (1) was a revolutionary event in the control of gastrointestinal worms. Although its spectrum of activity was narrow compared to modern anthelmintics and its dose level was rather high (600-800 mg kg-1), it was the veterinary anthelmintic of choice until the 1960s. 

Veterinary medicines must be used in accordance with their UK licence and as directed by a veterinary surgeon. Withdrawal periods between the end of the treatment and marketing of the animal for meat, must be not less than 14 days and/or three times the recommended time, whichever is the greater. Any meat from animals treated with growth promoters, artificial hormones, or organophosphorus and organochlorine pesticides cannot be sold as organic. 

Although this aspect is irrelevant to the assessment of residues and their implications for consumer safety, no account of the use of veterinary drugs would be complete without some passing mention which will restrict itself to considerations of safety in use of medicines rather than safety in their manufacture. Many formulations used in veterinary medicine offer very little scope for significant occupational exposure. Tablets and capsules for example ensure that occupational exposure is minimal, if not non-existent. However, operator exposure does occur and means need to be taken to reduce this. Organophosphorus compounds are... 

An established and well understood interaction. The organophosphorus pesticides are potent anticholinesterases used in agriculture and horhcul-ture to control insects on crops, and in veterinary practice to control various ectoparasites. They are applied as sprays and dips. Anyone who is exposed to these toxic pesticides may therefore show changes in their responses to neuromuscular blockers. Widely used organophosphorus pesticides include azamethiphos, bromophos, chlorpyrifos, clofenvinfos. 

T. C. Marrs, P. Edwards, Human adverse reactions to organophosphorus compounds used in veterinary medicines in Veterinary Pharmacovigilance. Adverse Reactions to Veterinary Medicinal Products, ed. K. N. Woodward, Wiley-Blackwell, Chichester, 2009, pp. 517 528. 

A special group was established to review adverse reactions to veterinary medicinal products in humans, the Appraisal Panel for Human Suspected Adverse Reactions. By 2000, the Appraisal Panel had considered a large number of adverse reactions in humans, including many relating to exposure to organophosphorus-containing dips. As a result, the Appraisal Panel realised that there was a similarity between the reported signs and symptoms in... 

Veterinary Products Committee, Report on Organophosphorus Sheep Dips, VPC, November, 1999. 

Compounds such as diazinon, an organophosphorus compound, are highly toxic to earthworms and other terrestrial organisms as well as to bees. However, concern has been expressed over the toxicity of the macrocyclic lactone endectocides used widely in large animal veterinary medicine. These... 

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