First clinical experiences with a new ovine Fab Echis ocellatus snake bite antivenom in Nigeria: randomized comparative trial with Institute Pasteur Serum (Ipser) Africa antivenom

• Published in: The American journal of tropical medicine and hygiene Vol. 56; no. 3; p. 291
• Main Authors: Meyer, W P, Habib, A G, Onayade, A A, Yakubu, A, Smith, D C, Nasidi, A, Daudu, I J, Warrell, D A, Theakston, R D
• Format: Journal Article
• Language: English
• Published: United States 01.03.1997
• Subjects: Adolescent; Adult; Aged; Animals; Antivenins - adverse effects; Antivenins - therapeutic use; Child; Dose-Response Relationship, Drug; Female; Half-Life; Humans; Immunoglobulin Fab Fragments - adverse effects; Immunoglobulin Fab Fragments - therapeutic use; Male; Middle Aged; Nigeria; Sheep; Snake Bites - therapy; Viper Venoms - antagonists & inhibitors; Viper Venoms - blood; Viperidae; Nigeria
• ISSN: 0002-9637
• DOI: 10.4269/ajtmh.1997.56.291

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 effective treatment and mortality and morbidity increased. To combat this crisis, a new monospecific ovine Fab antivenom (EchiTab) is being developed. Its theoretical advantages over conventional equine F(ab')2 antivenom are a more rapid tissue penetration and larger apparent volume of distribution (the volume of [tissue] fluid in which the the antivenom would be uniformly distributed to achieve the observed plasma concentration). In a preliminary study, two vials (20 ml; 1.0 g of protein) of EchiTab rapidly and permanently restored blood coagulability and cleared venom antigenemia in seven envenomed patients. Four experienced early reactions that responded to epinephrine. In a randomized 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 (Ipser) Africa polyspecific F(ab')2 antivenom, there were fewer reactions, but only 36% and 35% of patients, respectively, showed permanent restoration of coagulability, with the remainder requiring further doses. This suggests that 0.5 g (one vial) of EchiTab is approximately equivalent to 2.12 g (four ampules) of Ipser Africa antivenom, and that a higher initial dose will be required for most patients. Measurements of circulating venom and antivenom levels reflected the clinical events.