NAC Supplementation and Glutathione Regulation

Clinical Evidence

Administration of high-dose cysteine (81 mg/kg/day) via parenteral nutrition to preterm infants did not increase plasma cystine or GSH concentrations compared to lower doses (45 mg/kg/day) in a clinical setting, as reported by Clinical Nutrition 1, 2, 3, 4, 5
Parenteral cysteine supplementation did not increase erythrocyte GSH in neonates using tracer methodology, according to Clinical Nutrition 1, 2, 3, 4, 5
NAC supplementation at doses of 20-50 mg/kg/day in children requiring home parenteral nutrition tended to increase blood GSH levels but did not cause excess accumulation, as found by Clinical Nutrition 1, 2, 3, 4, 5
NAC has approximately 50% bioavailability when acetylated, limiting the amount available for glutathione synthesis, as reported by Clinical Nutrition 1, 2, 3, 4, 5

Documented adverse effects of NAC are primarily allergic reactions (nausea, vomiting, rare urticaria or bronchospasm) that can be managed with antihistamines and discontinuation if necessary, according to Hepatology 6, 7
In acetaminophen overdose management, NAC is given at very high doses (loading dose 150 mg/kg IV, followed by 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours) without causing glutathione toxicity, as reported by Hepatology 6, 7