L-Arginine/L-Citrulline Complex - Supports Peak Performance L-Arginine and L-Citrulline are two amino acids bundled into a single powerful supplement. Both are key intermediates in the Krebs urea cycle, where they participate in the detoxification of ammonia via the production of urea. In addition, any arginine not converted to urea enters general circulation where it is distributed to various tissues and metabolized for other uses such as protein synthesis. Free-form amino acid combination Arginine supports muscle metabolism and energy Arginine supports heart function and circulation Arginine easily converts into nitric oxide (NO) L-Arginine L-Citrullinne Complex supports liver detoxification L-Arginine is probably best known for its role in cardiovascular health and the formation of nitric oxide (NO). The formation of NO mediates smooth muscle relaxation in the blood vessel wall, and thus reduces the workload of the heart. Many nerve cells also use NO as a signaling molecule. Erectile function, for example, is mediated by the release of NO from the autonomic nerves in the penis. Also, L-Arginine is an important factor in muscle metabolism promoting energy during exercise and increased recovery after a workout.