In a retrospective nonrandomized study based on patient records, 30 patients receiving equine antiserum F(ab´)2 were compared with two patient groups (n=16, n=38) who were not given antivenom «Karlson-Stiber C, Persson H. Antivenom treatment in Vipera berus envenoming--report of 30 cases. J Intern Med 1994 Jan;235(1):57-61. »1. The patients treated with antivenom had significantly less severe oedema (23% vs 88%) and anaemia (10% vs 50%), and the number of hospital days was lower (median 3 days vs 6 days). The adverse effects included urticaria and serum sickness in 10% of the patients receiving antiserum.
A sheep antiserum consisting of Fab fragments has been compared with unpurified Fab serum in animal experiments «Smith DC, Reddi KR, Laing G, Theakston RG, Landon J. An affinity purified ovine antivenom for the treatment of Vipera berus envenoming. Toxicon 1992 Aug;30(8):865-71. »2. In mice the purified antiserum was three times as effective as the unpurified antiserum in the prevention of deaths caused by viper venom. On the basis of these results the purified antiserum is recommended as the drug of choice for severe snake bite reactions in humans.