title: 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.
abstract: 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.
authors.affiliation: Department of Chemical Pathology, Medical College of St. Bartholomew's Hospital, London, United Kingdom.
authors.forename: W P
authors.initials: WP
authors.lastname: Meyer
authors.forename: A G
authors.initials: AG
authors.lastname: Habib
authors.forename: A A
authors.initials: AA
authors.lastname: Onayade
authors.forename: A
authors.initials: A
authors.lastname: Yakubu
authors.forename: D C
authors.initials: DC
authors.lastname: Smith
authors.forename: A
authors.initials: A
authors.lastname: Nasidi
authors.forename: I J
authors.initials: IJ
authors.lastname: Daudu
authors.forename: D A
authors.initials: DA
authors.lastname: Warrell
authors.forename: R D
authors.initials: RD
authors.lastname: Theakston
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000997:Antivenins / Q000009:adverse effects / Q000627:therapeutic use*; D002648:Child; D004305:Dose-Response Relationship, Drug; D005260:Female; D006207:Half-Life; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009549:Nigeria; D012756:Sheep; D012909:Snake Bites / Q000628:therapy*; D014757:Viper Venoms / Q000037:antagonists & inhibitors* / Q000097:blood; D017819:Viperidae
chemical_list: D000997:Antivenins; D007140:Immunoglobulin Fab Fragments; D014757:Viper Venoms