Jarrow Formulas® Arginine-Citrulline Sustain™ is a synergistic combination of two amino acids to support nitric oxide (NO) production, blood flow and cardiovascular health. L-Citrulline largely converts to L-Arginine, increasing circulating and blood vessel levels of L-Arginine for NO production. Arginine-Citrulline Sustain provides these amino acids to the body over an 8 hour period.