This experiment was carried out in Veterinary Medicine at Iowa State University, USA. The ability of ryanodin to counteract the toxic effect of monensin was investigated by using adult male guinea-pigs. Heart rate and mean arterial blood pressure were measured. Data were collected every five minutes for one hour after drug injection then averaged. The toxic dose of monensin significantly (P<0.05) decreased the heart rate and mean arterial blood pressure of guinea-pigs. However, decreased heart rate and mean arterial blood pressure caused by monensin were significantly (P<0.05) increased by ryanodine. It is concluded that ryanodine has a potent to be used as a counteragent for monensin poisoning.