Renal crystal formation after combined or sequential oral administration of melamine and cyanuric acid

We evaluated renal melamine–cyanurate crystal spherulite formation after single and repeated ingestion of both melamine (MEL) and cyanuric acid (CYA) in catfish and trout. MEL and CYA were co-administered orally over a range of doses, 0.1–20 mg/kg body weight (bw) of each compound, either once or repeatedly for 4, 14 or 28 days (d). In catfish, the No Observable Adverse Effects Levels (NOAELs) for crystal formation for single, 4 d or 14 d dosing were 10, 2.5 and 0.5 mg/kg bw, respectively. In trout, the respective NOAELs were 2.5, 2.5 and 0.5 mg/kg bw. No renal crystals formed in catfish fed 0.1 mg/kg bw of each compound for 28 d. Sequential administration of 20 mg/kg bw of MEL followed by 20 mg/kg bw of CYA or vise-versa, with waiting periods of 1, 3, 7, 14 or 21 d between compound dosing also induced renal crystal formation in fish. These studies show that both catfish and trout are sensitive, non-mammalian models, for renal crystal formation following MEL and CYA ingestion. Since fish generally excrete chemicals more slowly than mammals, they may provide a “worst case scenario” model for higher risk populations, such as infants or persons with compromised renal function.     

A No Observable Adverse Effects Level (NOAEL) for pigs fed melamine and cyanuric acid

Ingesting melamine adulterated milk products led to kidney stones in many infants in 2008. This differs from the renal failure caused by intratubular crystal formation after co-ingestion of melamine (MEL) and cyanuric acid (CYA) in adulterated pet foods in 2007. To better understand the potential risk of developing crystal nephropathy following co-ingestion of MEL and CYA, we fed 16 weanling pigs 0, 1, 3.3, 10, 33, or 100 mg/kg bw/day of each MEL and CYA, or 200 mg/kg bw/day of either compound individually for 7 days. Crystals were found in the renal medulla and cortex and urine sediments of all pigs fed both MEL and CYA each at 10 mg/kg bw/day (or greater). Crystals were also found in one of the two pigs fed 200 mg/kg bw/day MEL-only. In a 28 day study, 36 weanling pigs were fed 0, 1, or 3.3 mg/kg bw/day of MEL and CYA or 200 mg/kg bw/day MEL-only. Only one of the 3.3 mg/kg MEL and CYA pig kidneys contained crystals. The no-observed-adverse-effect level (NOAEL) for pigs fed MEL and CYA for 28 days was concluded to be 1.0 mg/kg bw/day corresponding to 25 mg/kg (ppm) MEL and 25 mg/kg (ppm) CYA in dry feed.     

Characterization of deoxynivalenol-induced anorexia using mouse bioassay

A short-term mouse model was devised to investigate induction of food refusal by the common foodborne trichothecene deoxynivalenol (DON). DON dose-dependently induced anorexia within 2 h of exposure when administered either by intraperitoneal (ip.) injection or by oral gavage. The no observed adverse effect and lowest observed adverse effect levels in this assay were 0.5 and 1 mg/kg bw for ip. exposure and 1 and 2.5 mg/kg bw for oral exposure, respectively. DON’s effects on food intake were transient, lasting up to 3 h at 1 mg/kg bw and up to 6 h at 5 mg/kg bw. Interestingly, a dose-dependent orexigenic response was observed in the 14 h following the initial 2 h food intake measurement. Toxin-treated mice exhibited partial resistance to feed refusal when exposed to DON subsequently after 2 d, but not after 7 d suggesting that this modest tolerance was reversible. The short-term mouse bioassay described here was useful in characterizing DON-induced anorexia and should be applicable to elucidating mechanisms underlying this adverse nutritional effect.     

Investigation of melamine and cyanuric acid deposition in pig tissues using LC-MS/MS methods

Four LC-MS/MS methods were developed to quantify melamine (MEL) and cyanuric acid (CYA) in various pig tissues at or above the level of concern (2.5 mg/kg). Pigs treated with 200 mg/kg bw/day CYA daily for 7 days did not accumulate significant residue concentrations in muscle, liver or kidney. Pigs treated with 200 mg/kg bw MEL daily for 7 or 28 days had MEL residues in muscles (3–13 ppm), liver (2.8–14.1 ppm) and kidney (9.4–27.2 ppm). Treatment with MEL and CYA at 100 mg/kg bw of each triazine daily for 7 days resulted in MEL (26–59 ppm in muscle, 30–49 ppm in liver and 367–6300 ppm in kidney) and CYA (1.8–5.8 ppm in muscle, 2.6–6.5 ppm in liver and 303–7100 ppm in kidney). Treatment with MEL and CYA at 1, 3 or 10 mg/kg bw/day for 7 days did not result in residues greater than the level of concern in all tissues tested. Pigs dosed with 33 mg/kg bw/day of MEL + CYA for 7 days contained residues above the level of concern only in kidney. Deposition of MEL and CYA depends on the tissue type (muscles, liver and kidney), dosage and whether the triazines are given alone or in combination.     

Performance of urinary and gene expression biomarkers in detecting the nephrotoxic effects of melamine and cyanuric acid following diverse scenarios of co-exposure

Although standard nephrotoxicity assessments primarily detect impaired renal function, KIM-1, clusterin, NGAL, osteopontin and TIMP-1 were recently identified biomarkers proposed to indicate earlier perturbations in renal integrity. The recent adulteration of infant and pet food with melamine (MEL) and structurally-related compounds revealed that co-ingestion of MEL and cyanuric acid (CYA) could form melamine–cyanurate crystals which obstruct renal tubules and induce acute renal failure. This study concurrently evaluated the ability of multiplexed urinary biomarker immunoassays and biomarker gene expression analysis to detect nephrotoxicity in F344 rats co-administered 60 ppm each of MEL and CYA in feed or via gavage for 28 days. The biomarkers were also evaluated for the ability to differentiate the effects of the compounds when co-administered using diverse dosing schedules (i.e., consecutive vs. staggered gavage) and dosing matrixes (i.e., feed vs. gavage). Our results illustrate the ability of both methods to detect and differentiate the severity of adverse effects in the staggered and consecutive gavage groups at much lower doses than previously observed in animals co-exposed to the compounds in feed. We also demonstrate that these urinary biomarkers outperform traditional diagnostic methods and represent a powerful, non-invasive indicator of chemical-induced nephrotoxicity prior to the onset of renal dysfunction.     

Pre-clinical safety evaluation of the synthetic human milk,nature-identical,oligosaccharide 2′-O-Fucosyllactose (2′FL)

In order to match the composition of human breast milk more closely, it is now possible to supplement commercial infant formula (IF) with synthesised oligosaccharides that are chemically identical to human milk oligosaccharides. The safety data generated on a new human-identical milk oligosaccharide (HiMO), 2′-O-Fucosyllactose (2′FL), are presented. Standard in vitro genotoxicity tests were performed. To investigate the toxicological profile in a model representative of the intended target population, 2′FL was administered via gavage in a juvenile adapted sub-chronic rat study at dose levels of 0, 2000, 5000 and 6000 mg/kg bw/day. Fructooligosaccharide (FOS), currently acknowledged as safe and approved for use in IF, was used as a reference high-dose control at 6000 mg/kg bw/day. 2′FL was non-mutagenic in the in vitro assays. Oral administration up to 5000 mg/kg bw/day to rats over 90 days was not associated with any adverse effects based on clinical observations, body weight gain, food consumption, ophthalmoscopy, clinical pathology, organ weights and histopathology findings. Based on this 90-day study, a No Observed Adverse Effect Level (NOAEL) of 5000 mg/kg bw/day for both male and female rats was established for 2′FL. These findings support the safety of synthetic 2′FL for possible use in infant food.     

Plasma pharmacokinetics of melamine and a blend of melamine and cyanuric acid in rainbow trout (Oncorhynchus mykiss)

The objective of the study was to obtain pharmacokinetic parameters for melamine and blend of melamine (MEL) and cyanuric acid (CYA) in rainbow trout (Oncorhynchus mykiss). The single target dosage of MEL (20 mg/kg bw) and the blend of MEL and CYA (5 and 1.67 mg/kg bw, respectively) were designed and plasma samples were collected at 30 min, 1, 4, 8, 12, 20, 24, 36, 48, 72, 144 and 240 h sequentially. An optimized method for simultaneous determination of MEL and CYA in plasma and animal tissues by LC-MS/MS was used. The data were shown to best fit a non-compartment model with first order processes of linear characters for melamine, with half-life (t_1/2) of 32.2-32.9 h, clearance (Cl_z/F) of 35.9-36.6 ml/h/kg, and volume of distribution (V_ss) of 1.67-1.74 l/kg. Withdrawal of CYA was much more rapid than that of MEL with higher Cl_z/F (783.56 ml/h/kg) and shorter t_1/2 (7.92 h). T_max of MEL20 and MEL5 were 12 and 20 h, respectively, which showed that T_max of MEL5 was delayed when MEL and CYA were given together. The results are quite different from those in mammals and showed much slower elimination of MEL and CYA from rainbow trout body.     

Safety evaluation of an açai-fortified fruit and berry functional juice beverage (MonaVie Active)

The safety of an açai (Euterpe oleracea Mart.) pulp enriched fruit and berry juice, MonaVie Active^®, fortified with the functional ingredient, glucosamine, was studied. The beverage was found not to be mutagenic, clastogenic, cytotoxic, or genotoxic, as determined by the bacterial reverse mutation assay, chromosomal aberration assay, mouse micronucleus assay, and mammalian cell gene mutation (L5178Y) assay. The single dose LD50 based on a 14-day acute oral toxicity study is greater than 20,000 mg/kg bw, the highest dose tested. In a repeat dose 90-day oral subchronic toxicity study by gavage, 220 animals were randomly assigned to a control group, an untreated group, or one of three experimental groups (10, 20 and 40 g/kg bw). No treatment-related significant changes in body weight, food and water consumption, ophthalmology, organ weights, urinanalysis, hematological and clinical chemistry, or gross pathology, were observed in surviving animals compared to the control groups. Three animals died midway through the observation period (male, 20 g/kg bw/day; male 40 g/kg bw/day; and, female, 10 g/kg bw/day). These animals died without preceding clinical symptoms, histopathological lesions, or evidence of injury to tissue or organs except for signs of suffocation/aspiration congestion, which was concluded to be due to problems with the gavage administration of the fluid test article, and not due to the test article itself. The NOEAL was determined to be 40 g/kg bw/day for male and female rats, which was the highest dose tested. Phylloquinone (vitamin K1) content averaged 21.7 μg/100 g, comparable to amounts found in iceberg lettuce. In conclusion, the results provide additional experimental evidence that MonaVie Active^® juice is non-toxic.     

General 4-week toxicity study with EMS in the rat

In this subacute toxicity study, ethyl methanesulfonate (EMS) was administered daily by oral gavage to SPF-bred Wistar rats of both sexes at dose levels of 20, 60 and 180/120 mg/kg body weight (bw)/day for a period of 28 days (for 19 days in the high-dose group). A control group was treated similarly with the vehicle, bidistilled water, only. The groups comprised 10 animals per sex, which were sacrificed after 28 days, respectively 19 days in the high-dose group, of treatment. Additional five rats per sex and group were treated accordingly and then allowed a 14 days treatment-free recovery period. Additional six rats per sex and group (three rats per sex in the control group) were treated accordingly and used for hemoglobin adduct analysis after EMS exposure. All animals survived until their scheduled necropsy. Treatment with EMS had a direct dose-dependent effect on food consumption and consequently on body weight at doses ≥20 mg/kg bw/day in male rats and at ≥60 mg/kg bw/day in females rats. Hence, treatment with the high dose of 180 mg/kg bw/day had to be interrupted for 9 days after which, the animals were re-dosed at 120 mg/kg bw/day. This dose was also poorly tolerated over the remaining two treatment weeks causing again a marked reduction in food consumption and body weight. A dose of 60 mg/kg bw/day was moderately tolerated over 4 weeks treatment with mean daily food consumption and body weight distinctly lower than in controls. Primary targets of systemic toxicity were the hematopoietic system, thymolymphatic system and sexual organs. Characteristic changes in hematology parameters were decreased red blood cell counts, hematocrit, and hemoglobin concentration. White blood cell counts were also decreased due to reduced lymphocyte and granulocyte populations of each fraction. The corresponding histopathology findings were fatty atrophy of bone marrow and minimal hypocellularity of the white pulp of the spleen. Similarly, treatment with EMS caused an involution of the thymolymphatic system characterized by decreased organ weight of thymus, lymph nodes, and spleen microscopically associated with atrophy of the thymus and hypocellularity of Peyer's patches, lymph nodes and the white pulp of the spleen. The effects on sexual organs included lower organ weight/reduced size for testes, epididymides, seminal vesicles, prostate, and uterus. Tubular atrophy, single cell necrosis of the germ cells and in epididymides reduced spermatozoa were recorded microscopically. The described findings occurred at doses of 60 and 180/120 mg/kg bw/day and were dose-dependent with regard to incidence and severity. Other target organs were the pancreas (acinar cell vacuolation), thyroid gland (follicular cell hypertrophy), and salivary gland (secretory depletion of convoluted ducts). The systemic exposure to EMS was monitored by hemoglobin ethylvaline adduct measurement. The concentration of hemoglobin ethylvaline adducts was linear with the dose and accumulated 11–26-fold over the treatment period. In summary, decreases in food consumption and body weight were the dose-limiting effects of treatment with EMS. Organ toxicity was characterized by depression of cell proliferation (hematopoiesis and spermatogenesis) and changes suggestive of reduced metabolism and/or physiological imbalances (e.g. thymolymphatic system and thyroid gland) without signs of inflammatory or necrotic lesions. For some findings, especially the effects on the thymolymphatic system and sexual organs, it cannot be excluded that starvation-like condition contributed to the occurrence of such changes. The low dose of 20 mg/kg bw/day was basically free of adverse effects despite of a clear evidence for hemoglobin adducts.     

Acute and subchronic toxicity studies of pyrroloquinoline quinone (PQQ) disodium salt (BioPQQ™) in rats

The potential use of pyrroloquinoline quinone disodium salt (BioPQQ™), as a supplemental food ingredient, was evaluated in a range of oral toxicity studies in rats including an acute study, a 14-day preliminary and a 28-day repeated-dose study, and a 13-week subchronic study. The median lethal dose of BioPQQ™ was shown to be 1000–2000 mg/kg body weight (bw) in male and 500–1000 mg/kg bw in female rats. In the 14-day study, high doses of BioPQQ™ resulted in increases in relative kidney weights with associated histopathology in female rats only, while a follow-up 28-day study in female animals resulted in increases in urinary protein and crystals. These findings were reversible, and resolved during the recovery period. In the 13-week study, a number of clinical chemistry findings and histopathological changes were noted, which were deemed to be of no toxicological significance, as the levels were within the historical control range, were not dose-dependent, occurred at a similar frequency in control groups, or only occurred in the control group. Based on these findings, a no-observed-adverse-effect level of 100 mg/kg bw/day was determined for BioPQQ™ in rats, the highest dose tested in the 13-week study.     

A 90-day oral toxicity study on a new strain of Lactobacillus paracasei in rats

Lactobacillus paracasei is a species of bacteria that has been suggested to have probiotic benefits. To investigate the subchronic toxicity of L. paracasei GW080, a 90-feeding study was conducted in rats. Sprague-Dawley rats were randomly divided into four groups (10 rats/sex/group) and treated with 0, 1.25, 2.5, and 5.0 g/kg body weight (approximately equivalent to 0, 2.5 × 10⁹, 5.0 × 10⁹ and 1 × 10¹⁰ cfu/kg bw) of test material by gavage for 90 days. Daily clinical observations and weekly measurement of body weights and food consumption were conducted. Blood samples were obtained on day 46 and day 91 for the measurement of hematology and clinical chemistry parameters. Animals were euthanized for necropsy. Selected organs were weighted and recorded. Histological examination was performed on all tissues from animals in the control and high dose groups. No mortality, body weight, food consumption or treatment-related findings in clinical observations, macroscopic or microscopic examinations were observed. Differences between treated and control groups in some hematology and clinical chemistry parameters were not considered treatment-related. The no-observed-adverse-effect-level (NOAEL) for L. paracasei GM080 was considered to be 5.0 g/kg body weight (approximately equivalent to 1 × 10¹⁰ cfu/kg bw) for both genders, the highest dose tested.     

Characterisation and toxicological behaviour of Basic Methacrylate Copolymer for GRAS evaluation

Basic Methacrylate Copolymer is a fully polymerised cationic copolymer with taste-masking and moisture protection properties. It is used as a pharmaceutical excipient and has potential use as a glazing/coating agent to solid food supplements. This article describes available information on the safety of the substance.Oral administration of radiolabelled copolymer to rats showed the major route of excretion to be via the faeces. Minor absorption may occur at <0.02%. Safety studies revealed no adverse toxicity following repeated administration at up to 2000 mg/kg/day in a sub-chronic study in the rat or 750 mg/kg/day in a sub-acute study in the dog. No reproductive toxicity occurred at up to 1000 mg/kg/day in the rat. The substance shows no evidence of genotoxicity, has low acute toxicity and no irritation or sensitisation potential.As per the FDA approach an ADI of 20 mg/kg bw can be concluded. Daily exposure from use as a food additive is estimated as up to 11.7 mg/kg bw in adults and 13.3 mg/kg bw in children. In view of the high molecular weight of the substance, its lack of absorption and its low toxicity profile, the ADI is deemed adequate.     

Protective effect of catechin and quercetin on chlorpyrifos-induced lung toxicity in male rats

The mature male Wistar rats (n = 36, 300–320 g) were divided into six groups having six animals, i.e., Group I (control), Group II (catechin, 20 mg/kg bw), Group III (quercetin, 20 mg/kg bw), Group IV (chlorpyrifos 5.4 mg/kg, 1/25 LD50), Group V (catechin + chlorpyrifos) and Group VI (quercetin + chlorpyrifos). Rats were given chlorpyrifos, catechin and quercetin daily via gavage for 4 weeks. Chlorpyrifos increased the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT), and decreased glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities in lung tissues compared to the control group. In the catechin plus chlorpyrifos- and quercetin plus chlorpyrifos-treated groups, there were statistically significant increases in CAT and SOD activities, while no statistically significant changes were observed in MDA, GST and GPx activities relative to the control. Compared to the chlorpyrifos-treated group, however, the catechin plus chlorpyrifos- and quercetin plus chlorpyrifos-treated groups showed significantly increased GST and GPx activity, while the activity of MDA, SOD and CAT was significantly decreased. Light microscopic investigations revealed that 4 weeks of chlorpyrifos exposure induced numerous histopathological alterations in the lung. Milder histopathological changes were observed in animals co-treated with catechin plus chlorpyrifos or quercetin plus chlorpyrifos. Thus, it appears that catechin and quercetin ameliorate chlorpyrifos-induced lung toxicity but are not completely protective.     

Metabonomic analysis of quercetin against the toxicity of chronic exposure to low-level dichlorvos in rats via ultra-performance liquid chromatography–mass spectrometry

This study aims to determine whether quercetin elicits a protective effect against the toxicity of chronic exposure to low-level DDVP using metabonomic technology. Rats were randomly assigned into the control, DDVP-treated, quercetin-treated, and quercetin plus DDVP-treated groups. DDVP and quercetin were given to rats daily via drinking water and gavage respectively for 90 days. Eighteen metabolites, including the biomarkers of DDVP exposure (dimethyl phosphate, DMP) and quercetin exposure (quercetin and isorhamnetina), were identified from the metabonomic profiles of rat urine using ultra-performance liquid chromatography–mass spectrometry. Compared with the control group, the DDVP-treated group showed statistically significantly increased intensities of indoxyl sulfate, estrone sulfate, cholic acid, deoxycholic acid, p-cresol, p-cresol sulfate, and orotic acid but decreased intensities of suberic acid, citric acid, sebacic acid, hippuric acid, taurine, phosphocreatine, 3-hydroxyanthranilic acid, and kynurenic acid. The tendency of the aforesaid metabolites to change was significantly ameliorated in the quercetin (50 mg/kg·bw) plus DDVP (7.2 mg/kg·bw)-treated group compared with the DDVP-treated group. However, the levels of these metabolites in the quercetin plus DDVP-treated groups were still significantly different from those of the control group. These results indicate that quercetin has a partial protective effect on DDVP-induced toxicity.     

A subacute toxicity evaluation of green tea (Camellia sinensis) extract in mice

Green tea is believed to be beneficial to health because it possesses antioxidant, antiviral and anticancer properties. The potential toxicity of green tea when administered at high doses via concentrated extracts, however, has not been completely investigated. The objective of the present study was to evaluate the safety of green tea extract in ICR mice using a subacute exposure paradigm. In this study, mice were orally administered (gavage) green tea extract at doses of 0 (as normal group), 625, 1250 and 2500 mg/kg body weight/day for 28 days. The results showed that oral administration of green tea extract did not cause adverse effects on body weight, organ weights, hematology, serum biochemistry, urinalysis or histopathology. Additionally, administering green tea extract via gavage significantly reduced triglyceride and cholesterol levels. These observed effects could be attributed to the high levels of catechins present in green tea as these compounds have been reported to have beneficial health effects. The no-observed-adverse-effect level for green tea extract derived from the results of the present study was 2500 mg/kg body weight/day.     

Subchronic toxicity,toxicity to reproduction and prenatal developmental toxicity of vinyl laurate

Vinyl laurate (VL), is used in the manufacture of polyvinyl acetate vinyl laurate copolymer a component of gum base for chewing gum production. The potential toxicity of VL to reproduction was examined in a combined repeated dose and reproduction/developmental toxicity screening study (OECD test guideline 422) and a prenatal developmental toxicity screening study (OECD test guideline 414). VL was administered to Wistar rats by gavage at 0 (controls), 50, 250 and 1000 mg/kg bw/d. There were no signs of systemic toxicity in the parental animals of either study. Adverse effects on reproductive performance and fetal development that could be attributed to the VL treatment were not observed. Thus, the highest dose level tested was a NOAEL in these two studies.     

The threshold of toxicological concern for prenatal developmental toxicity

The Threshold Toxicological Concern (TTC) is based on the concept that reasonable assurance of safety can be given if exposure is sufficiently low. Originally based on the evaluation of carcinogenicity studies more recently TTC evaluations for other toxicological end points have been published. Here we report on the evaluation of our data base for oral developmental toxicity studies (OECD 414) in rats with 92 and 93 NOAEL values for maternal and developmental toxicity, respectively. The 5th percentile of the NOAEL distributions were calculated to be 4 mg/kg bw/d for maternal and 5 mg/kg bw/d for developmental toxicity. Adding the data for developmental toxicity provided by Kroes et al. (2004), a joint evaluation of 111 individual NOAEL values resulted in a 5th percentile value of 4 mg/kg bw/d. Using a safety factor of 500 (to account for a possible underrepresentation of chemical classes) on the 5th percentile a TTC value for developmental toxicity of 8 μg/kg bw/d based on the combined data and for maternal toxicity of 8 μg/kg bw/d based on our data base was calculated. Within the REACH context this value may serve as guidance whether to perform an animal experiment or to rely on a TTC value if estimated exposure is sufficiently low.     

Safety assessment of a solid lipid curcumin particle preparation: Acute and subchronic toxicity studies

Curcumin, a polyphenol, is obtained from turmeric, the ground rhizomes of Curcuma longa L. Extensive research over the past half century has revealed several health benefits of curcumin. The objective of the present study was to investigate potential adverse effects, if any, of a novel solid lipid curcumin particle (SLCP) preparation in rats following acute and subchronic administration. The oral LD₅₀ of the preparation in rats as well as in mice was found to be greater than 2000 mg/kg body weight (bw). In the subchronic toxicity study, Wistar rats (10/sex/group) were administered via oral gavage 0 (control), 180, 360, and 720 mg/kg bw/day of SLCP preparation for 90 days. Administration of the curcumin preparation did not result in any toxicologically significant treatment-related changes in clinical (including behavioral) observations, ophthalmic examinations, body weights, body weight gains, feed consumption, and organ weights. No adverse effects of the curcumin preparation were noted on the hematology, serum chemistry parameters, and urinalysis. Terminal necropsy did not reveal any treatment-related gross or histopathology findings. Based on the results of this study, the No Observed-Adverse-Effect Level (NOAEL) for this standardized novel curcumin preparation was determined as 720 mg/kg bw/day, the highest dose tested.     

Benzocaine-induced methemoglobinemia in an acute-exposure rat model

Tricaine methanesulfonate, a sedative for temporarily immobilizing fish, has a 21-day withdrawal time. Benzocaine has been proposed as an alternative sedative because a withdrawal period may not be required. Since benzocaine is known to induce methemoglobinemia, the potential for orally administered benzocaine to induce methemoglobin was assessed in rats. Sprague-Dawley rats were given a single gavage administration of 64 mg benzocaine hydrochloride per kg bw and then euthanized at intervals up to 120 min. Plasma levels of benzocaine were relatively low at all times, whereas methemoglobin peaked at 24 min. Additional rats were orally gavaged with 0-1024 mg benzocaine hydrochloride per kg bw and euthanized after 24 min. Plasma levels of benzocaine increased from 0.01 μM at 2 mg per kg bw to 2.9 μM at 1024 mg per kg bw. Methemoglobin levels did not differ from controls at doses up to 32 mg per kg bw in females and 64 mg per kg bw in males, whereupon the value increased to ∼80% at 1024 mg per kg bw. These data were used to estimate the potential impact of benzocaine residues in fish and suggest that the consumption of fish treated with benzocaine hydrochloride will not cause methemoglobinemia in humans.     

The threshold of toxicological concern for prenatal developmental toxicity in rabbits and a comparison to TTC values in rats

The Threshold Toxicological Concern (TTC) is based on the concept that reasonable assurance of safety can be given if exposure is sufficiently low. We report on the evaluation of BASF’s data for oral developmental toxicity studies in rabbits with 48 NOAEL values for maternal and developmental toxicity. The 5th percentile of the NOAEL distributions was calculated to be 5 mg/kg bw/d for both maternal and developmental toxicity. From literature 56 compounds tested in rabbits were taken and combined with values from BASF’s studies. The 5th percentile value for developmental toxicity of these 104 studies (mostly active ingredients) was 2 mg/kg bw/d. Thus, a TTC value of 4 μg/kg bw/d was calculated using a safety factor of 500 to account for relatively small database. This value is in the same range as the TTC value for developmental toxicity in rats of 8 μg/kg bw/d. The lower value may serve as guidance to determine whether further evaluation is needed or whether to rely on a TTC value for industrial chemicals or low concentration (environmental) contaminants if exposure is sufficiently low. A comparison of 30 compounds tested at BASF in both species, suggests that rabbits are not more sensitive than rats. We encourage others to publish data on rabbit developmental toxicity.