If you are taking creatine then you are only addressing half of the equation of muscle energy, recovery, and growth.

Creatine works by enhancing your muscle's energy supply and re-supply capacity through the anaerobic pathway. It does this by increasing concentrations of creatine phosphate, which is the muscle's immediate storage house for valuable phosphate ions. In the form of creatine phosphate, these ions are readily available to restore the activity of the primary muscle fuel ATP. Creatine phosphate works in conjunction with glycogen to provide immediate energy to the muscle. These compounds do not require the presence of oxygen to do their work, hence they are termed anaerobic (without oxygen) substrates.

The down side of the story is that creatine phosphate is quickly used up. In addition to this, anaerobic breakdown of glycogen for energy (glycolysis) soon comes to a halt as lactic acid builds up.

At this point it is time for the aerobic re-supply of ATP to take over. The aerobic energy system is complex and involves many metabolic pathways that use glucose, glycolytic byproducts, as well as fats for substrates.

Citrulline Malate ­ (Aerobic Creatine???˜
Creatine works by supporting and enhancing the anaerobic production of energy in the muscle. Unfortunately, it does nothing to address the production of aerobic energy in the muscle.

This is where citrulline malate comes in. Citrulline malate has been shown to increase aerobic ATP production in the muscle by 34%! The result is a marked decrease in fatigue and a substantial increase in aerobic exercise performance. Citrulline malate does this in part by stimulating the removal and utilization for energy of the lactic acid formed during anaerobic glycolysis.

Citrulline malate works synergistically with creatine in another way as well. After exercise your creatine phosphate levels are depleted and it takes a while for the free creatine in your muscles to be rephosphorylated. With citrulline malate, the rate of phosphocreatine recovery after exercise is increased by 20%! This means that you recover more quickly between weight training sessions giving yourself a better opportunity to grow faster.

Citrulline Malate and Ammonia
Ammonia is a toxic metabolic by product produced by your muscles, especially during intense exercise. Ammonia is removed from the body by the liver's urea cycle. Ammonia is very toxic to the body and muscles; the build up of ammonia in the body results in a rapid onset of fatigue. If the levels are not reduced, they can lead to muscle catabolism and interference with brain function. Severe ammonia toxicity can lead to organ failure, and eventually death.

Citrulline malate stimulates the urea cycle and therefore markedly increases the body's ability to remove ammonia. Ammonia is thus converted to the harmless by-product urea, and excreted from the body.