Title: Alternative Sweeteners

142 Stargel et al.
to 10,000 µg/plate with or without metabolic activation with liver S9 fraction
from Aroclor-induced rats. Neotame produced no evidence of mutagenic activity
in the mouse lymphoma cell gene mutation assay with and without metabolic
activation at concentrations ranging up to 800 µg/ml. No chromosomal aberrations
were detected in Chinese hamster ovary cells after exposure to concentrations
of neotame up to 500 µg/mL without metabolic activation and up to 1000
µg/mL with metabolic activation.
Neotame was administered by oral gavage to mice at doses up to 2000 mg/
kg body weight in a bone marrow micronucleus assay. Treatment with neotame
did not induce any changes in the ratio of polychromatic erythrocytes to total
erythrocytes or in the frequency of micronucleated polychromatic erythrocytes
in this assay system. No deaths, clinical signs of toxicity, or changes in body
weight occurred.
In addition to the mutagenicity evaluations with neotame, the major in vivo
metabolite that is also the major in vitro degradant, de-esterified neotame, was
not mutagenic in the Ames/Samonella assay and the xanthine-guanine phosphoribosyl
transferase mutation assay in Chinese hamster ovary cells. On the basis of
the results of in vivo and in vitro genotoxicity testing, neither neotame nor deesterified
neotame, the major metabolite and degradant, has the potential for mutagenicity
or clastogenicity.
F. Metabolism
Data from both humans and animals show that neotame has an excellent metabolic
and pharmacokinetic profile. All metabolites identified in humans were also
present in species used in safety studies. Neotame is rapidly, but incompletely,
absorbed in all species. Radiolabeled doses of neotame are completely eliminated.
The major route of metabolism is to de-esterified neotame. Methanol is produced
in equimolar quantities during the formation of de-esterified neotame whether
through metabolism or degradation; the maximum amount of methanol exposure
at projected 90th percentile consumption of neotame is negligible compared with
levels of methanol considered to be safe (13). Neotame does not induce liver
microsomal enzymes. On the basis of studies with albumin, neither neotame nor
de-esterified neotame is likely to interfere with binding to plasma proteins.
Neotame and de-esterified neotame have short plasma half-lives with rapid
and complete elimination. Peak plasma concentrations of neotame and deesterified
neotame after an oral dose occur approximately at 0.5 hour and within
1 hour, respectively. Neither neotame nor de-esterified neotame accumulate after
repeated dosing in humans or toxicology species. Absorbed neotame is rapidly
excreted in the urine and feces. In radiolabeled studies, most of the total radioactivity
was excreted as de-esterified neotame in the feces in all species and likely
reflects largely unabsorbed neotame in the gastrointestinal tract. A comparison