Thiafentanil and Etorphine Don ’ t Cause the Same Physiological Responses in Different Antelope Species
Dr Liesel Laubscher & Dr Silke Pfitzer
The development of highly potent opioid derivatives , first introduced in South Africa in the 1960s , revolutionised the use of medicines for the chemical restraint of wild herbivores . 1 , 2 Their high potency and wide therapeutic index make these medicines suitable for administration at high concentrations via projectile darts . Today , thiafentanil and etorphine are two of the most commonly used potent opioids for the immobilisation of wild ungulates . Both products produce profound analgesia , sedation and anaesthesia at very low doses , although the exact nature of the response can vary between species . 3
The effects of thiafentanil and etorphine are as a result of their activity at µ - , δ- and қ-opioid receptors . 4 – 9 µ -receptors are located throughout the brain and spinal cord and are responsible for most of the clinically relevant effects of opioids e . g . analgesia , sedation , catatonia and side effects such as respiratory depression . 10 , 11 Қ-receptors are found in the cerebral cortex , spinal cord and other brain regions and their activation results in spinal and supraspinal analgesia , mild sedation and dysphoria . The δ-receptors are located in the limbic system , cerebral cortex and spinal cord and their activation results in spinal and supraspinal analgesia , inhibition of dopamine release
10 , 11 and cardiovascular depression .
Etorphine is a semi-synthetic opioid derivative of oripavine that has a similar pharmacological profile to morphine . Etorphine has a much higher affinity for opioid receptors and is considered a pure µ - , δ- and қ-opioid receptor agonist . 4 – 7 , 9 , 13 Etorphine shows a rapid onset and relatively short duration of action
2020 ISSUE 02 11