Bosentan, a selective and more potent antagonist for Atractaspis envenomation than the specific antivenom

Preparation of an antivenom against Atractaspis had been done for the first time in the year 2007 in NAVPC in Riyadh, however, it was a lengthy and expensive process. In this study, an alternative treatment was tested using: 1- Nitroglycerin to antagonize the coronary vasospasm induced by the venom, 2- Bosentan to block the endothelin receptors since there is a similarity in structure and effect between the toxic fraction of venom (Sarafotoxins) and endothelins and 3- The specific Antivenom in comparison to nitroglycerin and bosentan. Pretreatment of rabbits with nitroglycerin, antivenom or bosentan completely protected all rabbits from the minimal lethal doses of venom or its toxic fraction. On the other hand, injecting any of the three drugs a few minutes (min) after injecting one minimal lethal dose (MLD) of the venom or the toxic fraction and at the first signs of ischemia, just before death, showed that bosentan completely saved all rabbits. In case of nitroglycerin all rabbits died and in case of antivenom, only 5 out of 10 rabbits were rescued. It is clear that bosentan is superior to the specific antivenom in protecting rabbits; this may be due to its higher affinity to endothelin receptors than sarafotoxins. This preclinical study shows a good potential in using bosentan as a selective antidote for atractaspis envenomation, especially in the African continent.