Move over arginine and citrulline, agmatine is the new household name when it comes to nitric oxide supplements.
Nitric oxide supplements or “vasodilators” are arguably the most popular exercise supplements next to creatine.
Given nitric oxide supplements’ popularity, it is worth examining how agmatine works, and its role in boosting exercise performance.
How Agmatine Works
Agmatine is a by-product caused by the breakdown of the amino acid arginine through a process called decarboxylation.
A study published in Proceedings of the Association of American Physicians revealed agmatine stimulates nitric oxide production by binding to a cell surface imidazoline receptor on endothelial cells and increasing cytosolic calcium. 
By acting directly on endothelial cells, agmatine relaxes blood vessels and improves circulation, functioning as a powerful vasodilator.
Additionally, agmatine acts as a neurotransmitter and stimulates luteinizing hormone release in the pituitary gland.  When the body senses an increase in luteinizing hormone, it responds by producing more testosterone. 
Agmatine and Muscle Building
As stated above, agmatine stimulates testosterone production, which plays a significant role in muscle growth and recovery. Furthermore, agmatine boosts anabolic hormones, such as human growth hormone (HGH), and acts as an antioxidant to protect cells.
A study examining bovines showed agmatine combined with HGH analogues stimulated greater HGH release than analogues with arginine. 
By increasing growth HGH, agmatine optimizes protein synthesis. In turn, protein synthesis drives amino acids into muscle cells for increased lean muscle mass. 
To maximize agmatine’s effectiveness, senior science editor Jim Stoppani from Flex recommends taking 500-1,000mg 30-60 minutes before workouts.
Additional Agmatine Benefits
In addition to improving vasodilation and boosting growth hormone, agmatine also appears to improve cognitive function. One study found agmatine to be an endogenous neuromodulator of mental stress
Agmatine was also shown to heighten insulin response.  Better insulin response means nutrients are more efficiently stored as glycogen, and decreases the chances macronutrients get stored as body fat.
Where You Can Find Agmatine?
Various manufactures sell agmatine as a bulk powder or in capsule form. Prices for agmatine on Amazon.com range from $20-$22.99. Agmatine is also available on Bodybuilding.com starting at $16.99 for the bulk powder.
Agmatine reviews on Bodybuilding.com are favorable, earning it 8.7 out of 10 with 15 total ratings.
To get an idea of how well agmatine has worked for others, let’s take a look at what a few agmatine reviews had to say:
This has easily become a top staple in my stack. I get better pumps post-workout and they last longer, as well as my muscles being fuller throughout the day. It mixes great, it is a little bitter but I add a fruit juice powder and that covers it right up. – Dunder
Should You Use Agmatine?
Agmatine appears to have the same benefits of increased growth hormone and vasodilation as arginine, but provides further cognitive and antioxidant support. Agmatine seems to be an excellent choice if you’re looking for a powerful arginine alternative, or just want to try something new.
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 THE ENCYCLOPEDIA GET THE FACTS. By: STOPPANNI, JIM, Flex, 87508915, Dec2011, Vol. 29, Issue 12
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 Ruth M. Shepherd, Molly N. Hashmi, Charlotte Kane, Paul E. Squires, Mark J. Dunne Elevation of cytosolic calcium by imidazolines in mouse islets of Langerhans: implications for stimulus-response coupling of insulin release British Journal of Pharmacology Volume 119, Issue 5, pages 911–916, November 1996