 influenc methemoglobinemia lethal toxic anion 1 azid time cours extent methemoglobinemia induc intraperiton sodium nitrit p-aminopropiophenon papp character femal mice peak methemoglobin format 34 achiev 40 minut compar level papp 15 achiev 5 10 minut declin rapidli normal nitrit- papp-induc methemoglobinemia afford degre protect poison sodium azid administ appropri time sequenc circumst protect mice death fluorid cyanat thiocyan selen borat prolong surviv time fluorid format azid-methemoglobin complex demonstr intact mous red blood cell small amount complex identifi vivo antidot situat protect action methemoglobinemia demonstr establish inhibitor cytochrom oxidas 