title: N-acetylcysteine in handgrip exercise: plasma thiols and adverse reactions.
abstract: N-acetylcysteine (NAC) is a thiol donor with antioxidant properties that has potential use as an ergogenic aid. However, NAC is associated with adverse reactions that limit its use in humans.
  
  
  OBJECTIVE
  The authors evaluated NAC efficacy as a thiol donor before handgrip exercise, measuring changes in serum cysteine and glutathione status and recording adverse reactions in adult subjects across a range of doses.
  
  
  METHODS
  Healthy individuals ingested NAC capsules (9 ± 2 or 18 ± 4 mg/kg) or solution (0, 35, 70, or 140 mg/kg). Venous blood samples were collected and subjects answered a questionnaire about adverse reactions.
  
  
  RESULTS
  Low doses of NAC (capsules) did not affect plasma cysteine or glutathione or cause adverse reactions. Adverse reactions to NAC solution were predominantly mild and gastrointestinal (GI). Intensity of GI reactions to 140 mg/kg NAC was significantly higher than placebo (in a.u., 0.67 ± 0.16 vs. 0.07 ± 0.04; p < .05). Plasma cysteine concentration increased with NAC dose from 9.3 ± 0.7 μM (placebo) to 65.3 ± 6.7 μM (140 mg/kg); however, there was no difference (p > .05) in plasma cysteine for 70 mg/kg vs. 140 mg/kg. Similar increases were observed for the ratio of cysteine to total cysteine, which was directly related to handgrip exercise performance. Plasma glutathione was elevated and oxidized glutathione diminished (p < .05) with NAC 140 mg/kg vs. placebo.
  
  
  CONCLUSIONS
  NAC effects on plasma thiols are maximized by oral administration of 70 mg/kg, a dose that does not cause significant adverse reactions.
authors.affiliation: Dept. of Physiology, University of Kentucky, Lexington, KY, USA.
authors.forename: Leonardo F
authors.initials: LF
authors.lastname: Ferreira
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Campbell
authors.forename: Michael B
authors.initials: MB
authors.lastname: Reid
mesh_terms: D000111:Acetylcysteine / Q000008:administration & dosage* / Q000009:adverse effects / Q000378:metabolism; D000328:Adult; D054874:Athletic Performance / Q000502:physiology; D018592:Cross-Over Studies; D003545:Cysteine / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005978:Glutathione / Q000097:blood; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013438:Sulfhydryl Compounds / Q000097:blood*; D055815:Young Adult
chemical_list: D013438:Sulfhydryl Compounds; D005978:Glutathione; D003545:Cysteine; D000111:Acetylcysteine