guanidine Guanidine: A strong organic base existing primarily as guanidium ions at physiological pH. It is found in the urine as a normal product of protein metabolism. It is also used in laboratory research as a protein denaturant. (From Martindale, the Extra Pharmacopoeia, 30th ed and Merck Index, 12th ed) It is also used in the treatment of myasthenia and as a fluorescent probe in HPLC.. guanidine : An aminocarboxamidine, the parent compound of the guanidines. | 2.39 | 2 | 0 | carboxamidine; guanidines; one-carbon compound | |