Doctor's Best Fast Acting Arginine Complex with Nitrosigine uses a patented bonded form of arginine silicate, clinically shown to significantly boost nitric oxide (NO) levels. NO is a key factor in increasing blood flow to working muscles. Engineered to take effect within 15 minutes, it delivers benefits through your entire workout for up to 6 hours - with a single dose! Continued use builds NO levels, which can boost flow and vessel flexibility.