Sustained plus immediate release l-arginine contains this conditionally essential amino acid in a bilayer tablet, with two tablets providing 500 mg of sustained release and 500 mg of immediate release l-arginine in a formula that allows for enhanced blood levels of this nutrient. most supplemental l-arginine is quickly absorbed into circulation and is extremely efficiently metabolized, yielding only a short-lived boost to l-arginine levels. sustained plus immediate release l-arginine tablets are specifically manufactured to immediately increase blood levels of l-arginine and then to sustain this beneficial increase continuously over an 8-hour period.*l-arginine has been shown to support the cardio- vascular system, promote vigorous heart function and enhance healthy circulation throughout the body through its conversion to nitric oxide.* research suggests l-arginine supplementation may also have positive benefits on athletic performance.*