Abbreviations: λz, terminal elimination constant; ADI, acceptable daily intake; AUC0-last, area under the curve from time zero until the last sampling time point; AE, adverse events; AUC, area under the plasma concentration-time curve; AUC-0.75-inf, AUC from time zero to infinity; AUClast, AUC to the last quantifiable observation; BLQ, below the limit of quantification; BMI, body mass index; bw, body weight; Cmax, concentration maximum; CSAF, chemical-specific adjustment factor; EE, efficacy evaluable population; EKG, electrocardiogram; HBsAg, hepatitis B surface antigen; IQR, interquartile range; IRB, Institutional Review Board; JECFA, Joint FAO/WHO Expert Committee on Food Additives; LC-MS/MS, liquid chromatography-tandem mass spectrometry; LLOQ, lower limit of quantification, LOQ, limit of quantification; NOAEL, noobserved-adverse-effect level; PP, per protocol population; SD, standard deviation; T1/2, half-life; Tmax, time to maximum concentration; WHO, World Health Organization * Corresponding author: Tel: +1-905-542-2900 E-mail address: ashley.roberts@intertek.com
AbstractThe acceptable daily intake (ADI) of commercially available steviol glycosides is currently 4 mg/kg body weight (bw)/day, based on application of a 100-fold uncertainty factor to a noobserved-adverse-effect-level value from a chronic rat study. Within the 100-fold uncertainty factor is a 10-fold uncertainty factor to account for inter-species differences in toxicokinetics (4-fold) and toxicodynamics (2.5-fold). Single dose pharmacokinetics of stevioside were studied in rats (40 and 1,000 mg/kg bw) and in male human subjects (40 mg/kg bw) to generate a chemical-specific, inter-species toxicokinetic adjustment factor. Tmax values for steviol were at ~8 and ~20 hours after administration in rats and humans, respectively. Peak concentrations of steviol were similar in rats and humans, while steviol glucuronide concentrations were significantly higher in humans. Glucuronidation in rats was not saturated over the dose range 40-1,000 mg/kg bw. The AUC0-last for steviol was approximately 2.8-fold greater in humans compared to rats. Chemical-specific adjustment factors for extrapolating toxicokinetics from rat to human of 1 and 2.8 were established based on Cmax and AUC0-last data respectively. Because these factors are lower than the default value of 4.0, a higher ADI for steviol glycosides of between 6 to 16 mg/kg bw/d is justified.
