Pharmacokinetics and metabolism of amitraz in ponies and sheep

The Evolution of Amitraz and Its Metabolic Degradation Products in Human Blood over 90 Days for Use in Forensic Determination

Amitraz is a pesticide that is often involved in poisoning cases. In determination process of poisoning cases, a problem often encountered is that when the evidence samples were examined, the poison had already decomposed, thus posing significant difficulty for obtaining evidences. In this study, we qualitatively and quantitatively tracked the metabolic degradation products of amitraz and ascertained that the metabolic degradation products were N,N'-bisdimethylphenylformamidine, N'-(2,4-dimethylphenyl)-N-methylformamidine (DMPF), 2,4-dimethylformamidine (DMF) and 2,4-dimethylaniline (DMA). It was found that although amitraz decomposed rather rapidly, the metabolic degradation products of amitraz persisted for quite a long time. This study demonstrates that forensic evidence in poisoning cases of amitraz can be obtained by the determination of DMPF, DMF and DMA. This study can provide insights on obtaining forensic evidences in poisoning cases.

Disposition Kinetics of Amitraz in Lactating Does

Amitraz, a member of the formamidine pesticide family, commonly used for ectoparasite control, is applied as a dip or low-pressure hand spray to cattle and swine, and the neck collar on dogs. Data on amitraz were generated mainly on laboratory animals, hens, dogs, and baboons. The data on the toxicity and disposition of amitraz in animals and its residues in the milk are inadequate. Therefore, the present study was intended to analyze the disposition kinetics of amitraz and its pattern of elimination in the milk of lactating does after a single dermal application at a concentration of 0.25%. Blood at predetermined time intervals and milk twice daily were collected for eight days post application. The drug concentration was assayed by high-performance liquid chromatography (HPLC). Amitraz was detected in whole blood as early as 0.5 h, which attained a peak concentration at 12 ± 5 h, followed by a steady decline; however, detection persisted until 168 h. Amitraz was present in the blood at its 50% Cmax even after 48 h, and was still detectable after 7 days. The disposition after a single dermal application was best described non-compartmentally. The mean terminal half-life (t1/2), mean residence time (MRT), and area under the curve (AUC0-t) were 111 ± 31 h, 168 ± 39 h, and 539 ± 211 µg/mL/h, respectively. The apparent volume of distribution (Vdarea) was 92 ± 36 mL/g with an observed clearance (Cl) of 0.57 ± 0.33 mL/kg/h. Thus, the drug was well absorbed, widely distributed and slowly eliminated from the animal body. Amitraz achieved milk concentration approximating 0.2 per cent of the total dose after a single exposure and the steady-state elimination of amitraz in milk above the recommended maximum residue limit (MRL) of 0.01 mg/kg can act as a source of public health concern when applied on lactating animals.

A preclinical large-animal model for the assessment of critical-size load-bearing bone defect reconstruction

Critical-size bone defects, which require large-volume tissue reconstruction, remain a clinical challenge. Bone engineering has the potential to provide new treatment concepts, yet clinical translation requires anatomically and physiologically relevant preclinical models. The ovine critical-size long-bone defect model has been validated in numerous studies as a preclinical tool for evaluating both conventional and novel bone-engineering concepts. With sufficient training and experience in large-animal studies, it is a technically feasible procedure with a high level of reproducibility when appropriate preoperative and postoperative management protocols are followed. The model can be established by following a procedure that includes the following stages: (i) preoperative planning and preparation, (ii) the surgical approach, (iii) postoperative management, and (iv) postmortem analysis. Using this model, full results for peer-reviewed publication can be attained within 2 years. In this protocol, we comprehensively describe how to establish proficiency using the preclinical model for the evaluation of a range of bone defect reconstruction options.

Pharmacokinetics and brain distribution of amitraz and its metabolites in rats

Amitraz is an acaricide and insecticide widely used in agriculture and veterinary medicine. Although central nervous system (CNS) toxicity is one of major toxicities following oral ingestion of amitraz, the understanding of the cause of the toxicity is limited. This study evaluated the systemic and brain exposure of amitraz and its major metabolites, BTS27271, 2',4'-formoxylidide, and 2,4-dimethylaniline following administration of amitraz in male Sprague-Dawley rats. Significant metabolism of amitraz was observed following the intravenous and oral administration. Amitraz related metabolites were majority of the total exposure observed, especially following oral administration. BTS27271 had higher brain exposure than amitraz and its other metabolites, which was due to low plasma protein binding but high brain tissue binding of BTS27271. Since BTS27271 has similar or higher toxicity and α₂-adrenoreceptor agonist potency than amitraz, its exposure in brain tissues may be the major cause of CNS toxicity of amitraz in animals and humans.

Potential environmental consequences of administration of ectoparasiticides to sheep

Sheep ectoparasiticides, which include the synthetic pyrethroids, the organophosphates, the 'insect'-growth regulators, the formamidines and the spinocyns, enter into the environment primarily through disposal of dip or fleece scours, as well as with contaminated faeces and urine. Due to the large quantities of spent dip, risks associated with environmental contamination are high. Synthetic pyrethroids and organophosphates pose risks to dung, soil and aquatic fauna; concerns over potential ecotoxicity to vertebrates and invertebrates have resulted in the cessation of their use in many countries. There is very little information regarding the ecotoxicity of 'insect'-growth regulators, formamidines or spinocyns, with no studies focussing on sheep. Here, the impact of sheep ectoparasiticides is discussed in terms of their potential to enter into the environment, their toxicity and their impact on ecosystem functioning. Where there are no data for excretion or toxicity of the ectoparasiticides used in sheep production, examples to demonstrate potential impacts are taken from laboratory ecotoxicity tests and the cattle literature, as well on work with foliar insecticides. Future research priorities are suggested to allow assessment of the environmental consequences of sheep ectoparasiticide treatments, which are essential for future sustainable sheep production.

Intoxicações natural e experimental por amitraz em eqüídeos: aspectos clínicos

A administração oral e a aspersão com amitraz reproduziram experimentalmente em 17eqüinos e um asinino um quadro de intoxicação muito similar a outro que vinha ocorrendo em cavalos no Estado do Rio de Janeiro. O início dos sintomas após a administração oral variou entre 15min. e 2h05min., na aplicação por aspersão variou entre 6h28min. e 8h38min. A evolução nos casos de administração oral foi de 4 a 9 dias, nos de aspersão de 5 a 6 dias. Somente morreram animais que receberam a administração oral. Um animal aspergido com o amitraz foi sacrificado. Por via oral foram usadas dosagens de 5,5 mg/kg (uma administração), 5,8 mg/kg (duas administrações) e num terceiro animal, doses que variaram entre 7,2 e 36,4 mg/kg (cinco administrações). Nas aplicações por aspersão, a intoxicação foi reproduzida com soluções nas concentrações de 0,1 e 0,2%. Com relação ao sistema nervoso, os principais sinais observados foram apatia, sonolência, ptoses palpebral e auricular, dificuldade de apreensão, mastigação e deglutição do alimento, arrastar das pinças dos cascos no solo, exposição do pênis, sensibilidade cutânea diminuída/ausente, instabilidade em estação, abdução dos membros, cabeça baixa, incoordenação, bocejos, flacidez labial, exposição da língua, cruzamento dos membros ao caminhar, resposta postural diminuída após cruzar e abduzir os membros, reflexos do lábio superior, palatal, lingual, de deglutição e flexor diminuídos/ausentes, reflexos auricular, palpebral e de ameaça diminuídos e resposta ambulatória diminuída ao teste de girar em círculo de pequeno raio. No que se refere ao sistema digestivo, foram evidenciados, principalmente, hipomotilidade/atonia intestinal, edema dos lábios, distensão abdominal, deitar e levantar com freqüência, rolar no solo, olhar para o flanco, gemer e impactação do intestino grosso. Observaram-se ainda taquicardia, aumento do tempo de preenchimento capilar e mucosas congestas, estridor, taquipnéia, dispnéia, secreção nasal, bradipnéia e respiração abdominal. Todos os três casos naturais ocorreram após aspersão do amitraz. Os primeiros sintomas foram observados 2 e 3 dias após o banho. A evolução foi de 6, 7 e 17 dias. Um animal manifestou a maioria dos sinais referentes ao sistema nervoso observados nos experimentos, com exceção dos sinais de cruzamento dos membros ao caminhar, bocejos, lábios flácidos e exposição do pênis. Outro animal, intoxicado espontaneamente, manifestou somente sintomas digestivos como rolar, ''patear'', hipomotilidade/atonia intestinal e impactação do intestino grosso. Um terceiro animal, inicialmente manifestou sintomas digestivos caracterizados por patear, rolar, atonia intestinal e impactação do intestino grosso, com conseqüente desenvolvimento de laminite; na fase final exibiu acentuada sintomatologia nervosa mostrando compressão da cabeça contra obstáculos, incoordenação motora com cruzamento dos membros ao caminhar e relutância em se movimentar. Baseados no quadro clínico observado, são sugeridos possíveis locais de lesão no sistema nervoso.