- Positive response to edrophonium in patients with neurotoxic envenoming by cobras (Naja naja philippinensis). A placebo-controlled study. Watt, G., Theakston, R.D., Hayes, C.G., Yambao, M.L., Sangalang, R., Ranoa, C.P., Alquizalas, E., Warrell, D.A. N. Engl. J. Med. (1986)