Lysine hydrochloride

Endpoint summary

Description of key information

Two reliable 28-day and two reliable 90-day studies are available.

In the 28-day key study (Fabreguettes, 1998) performed according to OECD 407 the NOEL of L-lysine HCl is 1940 mg/kg bw/d for rats (limit test), based on the absence of toxicologically adverse effects.

In a second 28-day study (Neda, 2001) there were no treatment-related adverse findings in this study, but there were treatment-related findings at high dose. The urinalysis showed an increasing tendency of lowered urinary pH value and a significant increase of total excretion amount of chlorine in both males and females in the 50000 ppm group. These changes were considered to be attributable to the fact that the test substance was a hydrochloric salt. However, the findings were considered to have no toxicological significance because no changes were observed in the serum potassium measured in the blood biochemistry examination. At the end of the administration period, a significant increase of relative weight of pituitary gland was noted in females in 12500 ppm and 25000 ppm groups, and significant  increases of absolute and relative weights of right kidney were noted in a female in 50000 ppm group, which were not considered to be treatment-related in the absence of a microscopic correlate. Based on the results of this study, i.e. no toxicologically significant changes were observed even in the group administered with Lysine hydrochloride at 50000 ppm level, the no-observable-effect-level (NOEL) for Lysine hydrochloride under the conditions of this study was considered to be 50000 ppm, corresponding to an average test compound intake of 4279 and 4487 mg/kg/day for males and females, respectively. 

In the 90-day key study (Mommers, 2003) performed according to OECD 408 there were considered to be findings of toxicological significance at high dose in this study. However, the decreased spleen weights at high dose in males (considered to be related to treatment) had no morphological correlate and can not be regarded as an adverse effect. The NOAEL may therefore actually be a dietary concentration of 5% (mean achieved dosage of 3002 and 3173 mg/kg bw/day for males and females, respectively). The decreased urinary pH for mid- and high dose males and high-dose females appears to be related to the administration of large quantities of an HCl salt.

In the second 90-day toxicity study (Tsubuku, 2004) the concentration of 5% lysine in dietary mixture corresponding to a mean achieved dosage of 3360 and 3990 mg/kg bw/day for males and females, respectively, was considered as No-Observable-Adverse-Effect-Level (NOAEL) in a 90-day study in Sprague- Dawley rats. There were considered to be no findings of toxicological significance in this study.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

914 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Justification for classification or non-classification

L-lysine HCl is not classified (67/548/EEC and CLP regulation) for repeated dose toxicity since no adverse effects in 28 and 90 days studies in rats were observed up to limit dose.