Characterization of the antinociceptive and sedative effect of amitraz in horses

Amitraz Poisoning - Tale of an Unusual Pesticide Poisoning: A Case Report

Amitraz is a formamidine group of compounds used in many parts of the world as an agricultural pesticide and an ectoparasiticide. Amitraz intoxication secondary to the oral, dermal or inhalational routes, both accidental and suicidal, has been encountered in humans leading to severe life-threatening side effects. Only very few cases of amitraz toxicity have been reported to date. This emphasizes the importance to ascertain amitraz intoxication from more commonly encountered pesticides like organophosphorus poisoning to avoid erroneous management of the patient. We report a case of a twenty-seven-year-old man who presented to the emergency room following suicidal ingestion of amitraz with the clinical manifestations of vomiting, altered sensorium, bradycardia and hypotension and complete recovery following supportive management.

Amitraz poisoning: Early gastric lavage can prevent life-threatening complications

Amitraz is a worldwide available pesticide of formamidine chemical family, proven to have reversible toxic effects on both animals and humans. Upon intoxication by ingestion, inhalation, or dermal route, it can cause various central nervous system (CNS), CVS, respiratory and gastrointestinal effects, some of which may be life threatening. Because of lack of specific antidote patients are usually managed with supportive and symptomatic management. We describe a case of 36-year-old female patient who presented to us with alleged history of 120 ml amitraz ingestion. She was given early gastric lavage with activated charcoal at emergency along with supportive and symptomatic management. She developed mild CNS depression, bradycardia, miosis, and fluctuating blood pressure. She was managed in intensive care unit and was kept under close hemodynamic monitoring. Her clinical course during hospital stay was uneventful and was successfully discharged without any residual deficits. According to previously published data, this amount of amitraz intoxication could have caused more serious clinical manifestations. This disproportionately less severe clinical manifestation in our patient is attributed to early gastric lavage. Ominous of reducing amitraz-related health hazards lies in the hands of primary health care physicians and regulatory bodies of government.

A Clinical Conundrum Called Amitraz Poisoning - A Case Report

Amitraz is a nonsystemic insecticide and acaricide which is sometimes also used as scabicide. Due to its widespread use, amitraz poisoning has emerged during the past decade and a half although the literatures on human intoxication cases are scarce. Amitraz poisoning can present with numerous symptoms involving central nervous, cardiovascular, and respiratory systems. The mainstay of treatment is supportive and symptomatic. We present the case of a 60-year-old gentleman who was shifted from another hospital in unconscious state with an alleged history of consumption of an unknown substance which later was known to be amitraz.

Amitraz, an underrecognized poison: A systematic review

Background & objectives:

Amitraz is a member of formamidine family of pesticides. Poisoning from amitraz is underrecognized even in areas where it is widely available. It is frequently misdiagnosed as organophosphate poisoning. This systematic review provides information on the epidemiology, toxicokinetics, mechanisms of toxicity, clinical features, diagnosis and management of amitraz poisoning.

Methods:

Medline and Embase databases were searched systematically (since inception to January 2014) for case reports, case series and original articles using the following search terms: ‘amitraz’, ‘poisoning’, ‘toxicity’, ‘intoxication’ and ‘overdose’. Articles published in a language other than English, abstracts and those not providing sufficient clinical information were excluded.

Results:

The original search yielded 239 articles, of which 52 articles described human cases. After following the inclusion and exclusion criteria, 32 studies describing 310 cases (151 females, 175 children) of human poisoning with amitraz were included in this systematic review. The most commonly reported clinical features of amitraz poisoning were altered sensorium, miosis, hyperglycaemia, bradycardia, vomiting, respiratory failure, hypotension and hypothermia. Amitraz poisoning carried a good prognosis with only six reported deaths (case fatality rate, 1.9%). Nearly 20 and 11.9 per cent of the patients required mechanical ventilation and inotropic support, respectively. The role of decontamination methods, namely, gastric lavage and activated charcoal was unclear.

Interpretation & conclusions:

Our review shows that amitraz is an important agent for accidental or suicidal poisoning in both adults and children. It has a good prognosis with supportive management.

Amitraz: a mimicker of organophosphate poisoning

Amitraz is used as an ectoparasiticide for dogs and cattle. Human poisoning due to amitraz may be misdiagnosed as organophosphate/carbamate (OPC) toxicity, since amitraz poisoning shares several clinical features (miosis, bradycardia and hypotension) encountered with OPC poisoning. A 19-year-old man with an alleged history of suicidal ingestion of a pesticide presented with drowsiness and was found to have constricted pupils, hypotension and bradycardia. He was diagnosed as a case of OPC poisoning and was treated with atropine and pralidoxime prior to presentation to our centre. Absence of a hypersecretory state, and the presence of hyperglycaemia and hypothermia along with a normal serum cholinesterase level suggested an alternate possibility. Retrieval of the poison container confirmed the diagnosis of amitraz poisoning. The patient made a rapid recovery with supportive management. Clinician awareness is key to successful management of this poisoning, which carries a good prognosis.

Amitraz poisoning treatment: still supportive?

Amitraz is a triazapentadiene, an α₂ adrenergic agonist and a member of the amidine chemical family. A limited number of human intoxication cases have been published in the literature. Lack of a clear and specific protocol for the therapy of amitraz intoxication may make its successfully managed case reports useful and valuable for other clinical practitioners in poisoning departments.

The case is about a 22 years old female, single, university student, ingested a glass of amitraz poison (about 100 mL of a 20% solution) as a suicidal attempt on 11:30 am which was about 3.5 h before her hospital admission. She found nausea, vomiting, and dizziness. Immediately, her family took her to a clinic near their house. At that clinic (13:30 pm) she had miosis and they did gastric lavage , one adult dose of activated charcoal (50 g) and referred her to our Poisoning Emergency Department, where she was managed supportively and successfully.

Amitraz is a poisonous chemical which may cause central nervous system depression and also respiratory/cardiovascular symptoms as well. Several studies reported that using atropine for those amitraz poisoned patients with both miosis and bradycardia resolved the problem and recommend it as the first line of drug therapy when bradycardia occurs from vagal stimulation and atrioventricular block.

Management of amitraz poisoning is still considered to be supportive and symptomatic. Although the effects of activated charcoal and cathartics have not been studied, they may still be considered for treatment.

Cardiovascular assessment in horses sedated with xylazine or amitraz

Cardiovascular effects due to intravenous (IV) xylazine (1.0mg/kg) or amitraz (0.1 or 0.4mg/kg) were evaluated in horses. Left ventricular function indexes, heart rate (HR), and cardiac output (CO) were measured by echocardiography. Second degree atrioventricular (AV) block was detected by electrocardiography. Invasive arterial blood pressure (AP) was also evaluated. All parameters were measured immediately before and during 60 minutes after drug injection. HR, CO, and second degree AV block were different between xylazine and amitraz-0.4mg/kg groups. Xylazine induced initial hypertension 10 minutes after injection, and hypotension was observed 30 minutes after amitraz-0.4mg/kg administration. Except for the second degree AV block which occurred only at five minutes, there was no change in the echocardiographic measurements after administration of amitraz-0.1mg/kg. Thus, amitraz-0.4mg/kg and xylazine (1.0mg/kg) induced similar cardiovascular side effects, but long-lasting action of amitraz-0.4mg/kg in the cardiovascular system was observed.

Effects of buprenorphine on nociception and spontaneous locomotor activity in horses

OBJECTIVE

To investigate spontaneous locomotor activity (SLA) and antinociceptive effects of buprenorphine in horses.

ANIMALS

6 healthy adult horses.

PROCEDURES

Horses received each of 3 treatments (10 mL of saline [0.9% NaCl] solution, 5 microg of buprenorphine/kg, or 10 microg of buprenorphine/kg). Treatments were administered IV. Order of treatments was randomized, and there was a 10-day interval between subsequent treatments. Spontaneous locomotor activity was investigated in a behavioral box by use of infrared photoelectric sensors connected to a computer, which detected movement of each horse. Antinociceptive effect was investigated by hoof-withdrawal reflex latency (HWRL) and skin-twitching reflex latency (STRL) after painful stimulation with a heat lamp.

RESULTS

Moderate excitement was observed in all horses from 5 to 10 minutes after the administration of both dosages of buprenorphine. The SLA increased significantly for 6 and 14 hours after IV administration of 5 and 10 microg of buprenorphine/kg, respectively. Values for HWRL increased significantly only at 30 minutes after injection of 5 microg of buprenorphine/kg, whereas STRL and HWRL each increased significantly from 1 to 6 hours (except at 2 and 4 hours) and 11 hours, respectively, after injection of 10 microg of buprenorphine/kg.

CONCLUSIONS AND CLINICAL RELEVANCE

IV injection of buprenorphine caused a dose-dependent increase in SLA, but only the dose of 10 microg/kg induced analgesia on the basis of results for the experimental method used.

Efeitos da administração epidural de amitraz, xilazina ou dimetil sulfóxido em vacas

Avaliaram-se os efeitos da injeção epidural de amitraz (0,4mg/kg), xilazina (0,05mg/kg) ou dimetil sulfóxido 10% (5,0ml) sobre a freqüência cardíaca (FC), pressão arterial sistólica (PAS), freqüência respiratória (FR), motilidade ruminal (MR), temperatura retal (TR), altura de cabeça (AC) e latência das respostas a estímulos nociceptivos nas regiões da coxa (LECC) e coroa do casco (LRRM) de vacas. Houve diminuição da FC e da MR nos grupos xilazina e amitraz. O tratamento com xilazina resultou em alterações na FR, PAS e AC. LECC e LRRM foram maiores nos tratamentos com agonistas alfa-2. Nas doses utilizadas, o amitraz aumentou a latência de resposta a estímulo nociceptivo em menor grau que a xilazina, sem induzir efeitos colaterais sistêmicos severos, em vacas.

Comparative study of the sedative and antinociceptive effects of levomepromazine, azaperone and midazolam in laboratory animals

The sedative and antinociceptive effects of levomepromazine, azaperone and midazolam were studied in rats and mice using three behavior evaluation methods. Both exploratory behavior and spontaneous locomotor activity were significantly diminished in a spontaneous locomotor activity test in open field when using levomepromazine and azaperone. However, the azaperone effects were short lived in comparison to levomepromazine effects. Midazolam caused reduction in exploratory activity with no effect in spontaneous locomotion. When assessing the antinociceptive effect in the tail flick reflex latency test after infliction of a pain stimulus in rats, tested drugs did not show any antinociceptive effect. The drugs studied were able to abolish the writhing reflex in mice when compared to control. Levomepromazine, azaperone and midazolam, at the doses were able to inhibit the exploratory behavior in rats, proving their sedative effect. Regarding the antinociceptive effects for visceral pain, these drugs were able to block contortions in mice.

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.

Amitraz poisoning, an emerging problem: epidemiology, clinical features, management, and preventive strategies

BACKGROUND

Amitraz is a pharmaceutical, veterinary, and agricultural product which is used worldwide under numerous generic names as an acaricide and insecticide. Because of its widespread use amitraz poisoning has come emerged as a cause of childhood poisoning during the past decade, particularly more in certain countries such as Turkey.

AIMS AND METHODS

To report the clinical features, the management, and the preventive strategies of amitraz poisoning in nine children, and review the previously reported 137 cases in humans.

RESULTS

Five male and four female children aged 10 months to 8 years were admitted to our department. The estimated ingested dose ranged between 89.2 and 163 mg/kg and estimated time from ingestion to presentation was 30-120 minutes. The initial signs and symptoms were impaired consciousness, drowsiness, vomiting, disorientation, miosis, mydriasis, hypotension, bradycardia, tachypnoea, hypothermia, and generalised seizures. Hyperglycaemia, glycosuria, and minimal increase in transaminase levels were observed. None required mechanical ventilation. CNS depression resolved spontaneously within 4-28 hours in all. The length of hospital stay was two to three days; all had a good outcome.

CONCLUSION

This review details preventive measures and management strategies of amitraz poisoning, including the importance of following patients closely in the intensive care unit, monitoring their respiratory, cardiovascular, and central nervous systems since they may occasionally experience serious cardiopulmonary side effects.

Toxicological evaluation of long-term intravenous administration of amitraz in horses

With the aim of determining the possible toxicity of amitraz after its prolonged use in horses, six English Thoroughbred horses received intravenous injections of amitraz (0.05, 0.10 or 0.15 mg/kg) weekly for four months, constituting the experimental group. Eight other animals (control group), via the same route following the same drug administration schedule and period of time, received the vehicle, dimethylformamide. At the end of this period, blood was collected from all the animals, and a comparison was made of the means of the values obtained for the various blood analyses: complete hemogram, alkaline phosphatase, gamma-glutamyltransferase, blood urea nitrogen, lactate dehydrogenase, aspartate aminotransferase, creatine phosphokinase, glucose, albumin, total protein, creatinine, Na+ , K+, Cl- and CO2. The results for the biochemical characteristics showed that only the mean value for urea of the animals submitted to treatment with amitraz was significantly different than the mean value obtained for the control group. The analyses of the hematological characteristics showed that no significant differences between groups were observed. Similarly, the measurement of blood electrolyte levels demonstrated that long-term treatment with amitraz did not cause significant changes in the variables analyzed. The results indicate that amitraz, given in the doses employed in this study, did not show signs of inducing toxic effects in vital organs, even after prolonged administration.

Effect of amitraz and xylazine on some physiological variables of horses

The effect of the intravenous injection of amitraz (0.1mg/kg) to horses on cardiac activity, respiratory rate, intestinal motor activity, rectal temperature, sweating and masticating was evaluated and compared to the effect of intravenous administration of xylazine (1mg/kg, iv) on heart rate, respiratory rate and intestinal activity. Amitraz caused a significant decrease in heart activity, respiratory rate and intestinal movements, but these effects were not as pronounced as those caused by xylazine. Amitraz also caused a significant relaxation of the rectal smooth muscle, and an apparent increase in sweating and in the frequency of horses found masticating hay. Rectal temperature was not influenced by amitraz. The results indicated that amitraz, at the dose used, did not cause severe side effects in horses.