pentamethonium

noun

pen·​ta·​me·​tho·​ni·​um ˌpent-ə-me-ˈthō-nē-əm 

: an organic ion [C₁₁H₂₈N₂]²⁺ used in the form of its salts (as the bromide and iodide) for its ganglionic blocking activity in the treatment of hypertension