Any of a class of compounds consisting of a methylene chain with a trimethylammonium group, (CH₃)₃ N+, at each end, some of which are used as ganglionic blocking agents; a salt of such a compound. Chiefly attributive, especially in "methonium compound".
In the names of individual methonium compounds the number of methylene groups in the chain is indicated with a numerical prefix.
1950s; earliest use found in The Lancet. From -methonium.