Agmatine is a byproduct of the decarboxylation of arginine, another popular supplement used in preworkout formulas. Both of the aforementioned amino acids can be converted to nitric oxide; however, agmatine is advantageous because its structure results in more nitric oxide production, gram for gram. Agmatine's molecular structure also allows it to deliver its pump inducing effects much faster.
In the body, agmatine is found in every living cell. It's part of the class of amines known as polyamines, which are responsible for acting as bioregulators of a variety of cellular functions. Some of these include the regulation of cell growth and division as well as maintaining proper cell membrane phospholipid content.  Dietary sources of agmatine include fish, meat, eggs, soy, and even beer and chocolate.>
500mg doses are recommended for optimal results. Some users prefer to use agmatine in a cyclic manner, such as 3 days on and 1 day off, or 5 days on and 2 days off, to help minimize tolerance buildup.
Side effects associated with agmatine are very rare, with gastrointestinal discomfort being associated with excessive consumption.