Signs and possible mechanism of action in amitraz poisoning
| Signs | Mechanism of action |
|---|---|
| Hypotension | Central α2 adrenoceptor agonist stimulates presynaptic receptors and causes hypotension, and diminishes peripheral sympathetic tone, lowering the blood pressure1,16 with augmentation by the depressive effects of xylene4 |
| Bradycardia | Central α2 adrenoceptor agonist effect whose action results in diminished peripheral sympathetic tone with a lowering of heart rate1,41 |
| In the animal study conducted by Cullen and Reynoldson,16 both yohimbine (α2 adrenergic antagonist) and prazosin (α1 adrenergic antagonist) partially inhibited the bradycardia produced by amitraz. Thus, it might be concluded that both adrenoceptor subtypes appear to be stimulated to produce bradycardia | |
| Xylene contributes to bradycardia by its depressive affect on the central nervous system4 | |
| Miosis and mydriasis | While the low doses of α2 adrenergic agonists induce miosis (presynaptic effect), the higher doses cause mydriasis (postsynaptic effect)42–44 |
| Bradypnoea | Bradypnoea occurs by inhibition of response against CO2 via direct effect of the agent on respiratory centre42,43 |
| Altered mental status | α2 adrenoceptor stimulation causes sedation and unconsciousness4,35 |
| Xylene may also induce altered mental status1,4,45 | |
| Hypothermia | The animal study conducted by Hugnet and colleagues35 showed that hypothermia could be related to the α2 agonist activity of amitraz because it was reversed by low doses of atimepazole, a potent α2 antagonist, within 10 minutes after injection |
| Vomiting | It is not probably an effect due to α2 adrenergic agonist activity as it has not been noted in animal experiments with amitraz alone.4 It is probably due to the petroleum distillates mixed with amitraz in commercial preparations1,4 |
| Convulsion | Neurotoxic and proconvulsant effects are triggered by α2 receptors partially18 |
| Polyuria | α2 adrenoceptor stimulation decreases antidiuretic hormone (ADH) and renin secretion, inhibition of ADH effect, and enhanced diuresis by increased glomerular filtration rate43 |
| Gastrointestinal hypomotility | α2 adrenoceptor stimulation causes hypomotility46,47 |
| Hyperglycaemia | α2 adrenoceptor stimulation reduces insulin secretion and causes hyperglycaemia.36 The animal study conducted by Abu-Basha and colleagues48 showed that amitraz inhibited insulin and stimulated glucagon secretion from the perfused rat pancreas, and inhibited insulin secretion |