Pharmacokinetics and Safety of Single and Multiple Doses of Oral N-Acetylcysteine in Healthy Chinese and Caucasian Volunteers: An Open-Label, Phase I Clinical Study

Introduction: Few studies have evaluated whether the pharmacokinetics of N-acetyl-cysteine (NAC) are different in Chinese and Caucasian individuals. Methods: This single- and multiple-dose, single-centre, open-label, phase I clinical study was conducted in healthy adult volunteers. All participants received oral NAC 600-mg uncoated tablets, which were administered first as a single dose and, following a 48-h wash-out period, twice daily for 3 days. Blood and urine were collected after single- and multiple-dose NAC administration. Adverse event (AE) data were collected throughout the study. Results: Fifteen Chinese and 15 Caucasian (mostly Italian) individuals (males 66.7%, mean age 36.8 years) participated in the study. Pharmacokinetic characteristics of NAC were similar in the two cohorts. Following both single- and multiple-dose administration, plasma concentration of NAC increased rapidly, reaching a peak at approximately 1.0 h. Maximum plasma concentration and extent of exposure were higher after multiple doses than after a single dose. The accumulation ratio was relatively consistent in both Chinese (mean ± standard deviation 1.5 ± 0.4) and Caucasian (1.4 ± 0.2) participants. The half-life was 15.4 h in Chinese and 18.7 h in Caucasian participants, and the fraction of NAC excreted in urine in the 36 h following administration was 3.7% in Chinese and 3.8% in Caucasian participants. Two Caucasian participants had a total of 3 AEs (headache, presyncope and dysmenorrhoea). No AEs occurred in Chinese participants. Conclusions: The pharmacokinetic characteristics of NAC are similar in healthy Chinese and Caucasian individuals after single and repeated administration. NAC has a favourable tolerability profile.