FIRST CLINICAL-EXPERIENCES WITH A NEW OVINE FAB ECHIS-OCELLATUS SNAKEBITE ANTIVENOM IN NIGERIA - RANDOMIZED COMPARATIVE TRIAL WITH INSTITUTE-PASTEUR SERUM (IPSER) AFRICA ANTIVENOM

During the past decade, effective snake antivenoms have become scarce in northern Nigeria. As a result, many patients severely envenomed by the saw-scaled or carpet viper (Echis ocellatus), which is responsible for more than 95% of the snake bites in the region, did not receive e ffective treatment and mortality and morbidity increased. To combat th is crisis, a new monospecific ovine Fab antivenom (EchiTab(TM)) is bei ng developed. Its theoretical advantages over conventional equine F(ab ')(2) antivenom are a more rapid tissue penetration and larger apparen t volume of distribution (the volume of [tissue] fluid in which the th e antivenom would be uniformly distributed to achieve the observed pla sma concentration). In a preliminary study, two vials (20 ml; 1.0 g of protein) of EchiTab rapidly and permanently restored blood coagulabil ity and cleared venom antigenemia in seven envenomed patients. Four ex perienced early reactions that responded to epinephrine. In a randomiz ed comparative trial of one vial (10 ml; 0.5 g protein) of EchiTab or four ampules (40 ml; 2.12 g of protein) of Institute Pasteur Serum (Ip ser) Africa polyspecific F(ab')(2) antivenom, there were fewer reactio ns, but only 36% and 35% of patients, respectively, showed permanent r estoration of coagulability, with the remainder requiring further dose s. This suggests that 0.5 g (one vial) of EchiTab is approximately equ ivalent to 2.12 g (four ampules) of Ipser Africa antivenom and that a higher initial dose will be required for most patients. Measurements o f circulating venom and antivenom levels reflected the clinical events .