Chromatographic evaluation of urinary N-Acetyl-L-Cysteine: an ergogenic drug.

N-Acetyl Cysteine (NAC) is a sulphidryl group donor widely used since many years in the treatment of respiratory disorders and in paracetamol poisoning. Its principal properties however are related to its activity as a direct free radical scavenger and to its capacity of increasing intracellular cysteine levels thus potentiating cell natural defence mechanisms against oxidative damage. Recently NAC (150 mg/kg intravenous) has been used to increase by over 15% the forces sustained during muscular fatigue induced by low stimulus frequencies. Application of NAC in sport medicine as enhancer of performance in endurance exercise (e.g. cycling or running) will be limited by important side effects of the drug but it is likely a different way of administration or a different scavenger would overcome this problem. If controlled trials will be able to confirm any positive effects in muscular fatigue inhibition, NAC could have important practical implications in professional sports and could be added to the list of banned substances. In light of recent interest in the relationship of NAC to fatigue it is essential that a facile, reliable assay be devised for its determination in biological fluids. We have set up a Chromatographic HPLC method for acetyl cysteine determination in urine samples. This isocratic procedure, fast and requiring no elaborate pre-assay work, could help to set urinary concentrations in case of therapeutical use (200-600 mg/day) or when elevated levels are assumed as doping agent in order to impart an unfair advantage in endurance test.