Propionyl-L-carnitine-d 3 (hydrochloride) is deuterium labeled Propionyl-L-carnitine. Propionyl-L-carnitine is a carnitine derivative and has a high affinity for muscular carnitine transferase. Propionyl-L-carnitine increases cellular carnitine content, thereby allowing free fatty acid transport into the mitochondria. Propionyl-L-carnitine alleviates the symptoms of PAD through a metabolic pathway, thereby improving exercise performance.