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EC number: 200-460-4
CAS number: 60-18-4
In the current study the effect of a single oral administration of a
high dose of tyrosine was investigated. More in detail the behavior of
the rats was evaluated with a computer pattern recognition system. The
study was not according to OECD or GLP, however, the animals were
observed for 2 weeks. There were 2 dosing groups, 309 and 618 mg/kg,
each containing 15 animals and each group was linked to a control group
of 15 animals. Amphetamine was used as positive control.
No animals died and no adverse effects were observed during the course
of the study. Amphetamine clearly increased the total time the rats
engaged in walking, turning, and head turning, and thus influenced the
No LD50 was determined in the study, however, we can derive it and state
that the LD50 is > 618 mg/kg bw.
In this current study the potential toxicity of L-tyrosine was
evaluated in a 13-week repeated-dose oral toxicity study in rats
according to OECD 408. The study was not GLP. L- tyrosine was
administered by gavage to 4 groups each consisting of 10 males and
10 females. The doses were 0 (vehicle: water), 200, 600 or 2000
No deaths occured during the administration period in any of the
study groups. No L-tyrosine-related changes were observed in
clinical signs, body weight, food and water consumption,
ophthalmology or necropsy.
Some L-tyrosine-related changes were observed in the stomach, the
liver and kidneys.
Additionally, significant changes were seen in biochemical
Cataract formation was not observed in this study at any dose
Even though this study is not an acute toxicity study, based on
the above results, we can assume that the LD50 for males and
females will be > 2000 mg/kg bw/d because after 90 days of dosing
no animal died.
Acute oral toxicity
In the study of Mullenix the administration dose was not as high as
recommended in the guideline. Also, the focus of the study was
behavioral observation. However, no animal died during the observation
period of 2 weeks. Additionally, there is a 90-days repeated dose
toxicity study available according to OECD 408 in which rats were orally
dosed up to 2000 mg/kg bw for 13 weeks and the no animal died during
this period. Taking together in a weight-of-evidence approach no new
acute toxicity test is needed, as the available information is
As no mortality was observed in the available publications at a dose of
2000 mg/kg bw/d, the test item is not to be classified for acute oral
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