Potency assay of antivenom: Batch to batch variation of neutralising efficacy of antivenom

Neutralisation of biological properties of Russell's viper venom (Thayawady) with 4 different batches of monospecific lyophilised antivenom manufactured by Myanmar Pharmaceutical Factory (batch DN 84560B exp. 2/90, DN 86608B exp. 4/92, DH 89652A exp. 9/94 and DD 90668B exp. 6/95) was assessed in rodents using WHO standard tests of neutralising activity. The amount of antivenom required to neutralise different biological properties of venom by different batches of antivenom varied from 2 to 50 times. Such variation of antivenom potency may explain failure of correction of some venom-induced effects seen in antivenom treated Russell's viper bite cases as well as variation in the composition of venom used as an immunogen. No quantitative differences in bands recognised by different antivenoms was observed in immunoblot. It is suggested that characterisation of widely pooled potent venoms to be used for antivenom production and potency assay of antivenom should be carried out routinely.