Positive Response to Edrophonium in Patients with Neurotoxic Envenoming by Cobras (Naja naja philippinensis)

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Abstract
To study the ability of anticholinesterase drugs to reverse the potentially fatal paralytic effects of cobra venom, we conducted a placebo-controlled, double-blind crossover trial of intravenous edrophonium (Tensilon) in 10 adults with neurotoxic envenoming caused by bites of the Philippine cobra (Naja naja philippinensis). There was significantly more improvement in ptosis and endurance of upward gaze after edrophonium than after placebo. Five minutes after injection, the mean difference (±SD) in the percentage of the iris that was uncovered was 39±5.47 (70 vs. 31 percent; P<0.01), and the mean difference in the number of seconds of upward gaze was 33.1±9.29 (39.7 vs. 6.6 seconds; P<0.01). The expiratory and inspiratory pressures, forced vital capacity, and ability to cough, speak, and swallow also improved after edrophonium. In both the patients who were studied electromyographically, pretreatment and postplacebo responses were typical of myasthenia gravis and became normal after edrophonium.