Calculation of effective dose fifty (ED₅₀) of antivenom for American pit viper envenomation

The use of conventional approved snake antivenom is the most reliable snake envenomotherapy at the moment. However, because of post-treatment hypersensitivity reactions sometimes caused by large doses of snake antivenoms, the treatment of snake poisoning needs to be reviewed. The effective dose fifty (ED₅₀) of snake antivenom was calculated for 11 American pit viper envenomation as reported by Consroe et al. Four different ED₅₀ formulas were used to determine effective dose fifty of snake antivenom against LD₅₀ of the snake venoms using intravenous route. The findings revealed that snake envenomotherapy is in monotonic dose-response fashion with each formular producing ED₅₀ value for specific snake. The difference in values may be due to species of snakes and the types of ED₅₀ formula used. All the ED₅₀ formulas with the LD₅₀ as numerator yielded higher effective therapeutic dose of snake antivenoms and corresponding higher LD₅₀ values of snake venoms. The lower the denominator, the lower the LD₅₀ and the ED₅₀ value, and the lower the chance of hypersensitivity reaction, but the higher may be the chance of the snake antivenom failure. Therefore, Saganuwan’s formula \( \left({\mathrm{LD}}_{50}=\frac{ED_{50}}{3}\ x\ Wa\ x\ {10}^{-4}\right) \), whereas Wa is weight of animal, could produce effective envenometherapy with low chance of hypersensitivity reactions.