LD50 In Rats Research Articles

Health and Ecological Effects of Adiponitrile

Adiponitrile (ADN) has moderate acute toxicity with an oral LD50 in rats of 100 to 500 mg/kg and a 4‐hr LC50 in rats of 1.71 mg/L (vapor plus aerosol). ADN produced slight eye but no skin irritation in rabbits. Repeated exposures by inhalation produced changes in the hematologic profile with effects seen at 100 or 300 mg/m3. The hematologic changes were reversible upon cessation of further inhalation exposures. Dogs fed up to 500 ppm (equivalent to 12–15 mg/kg) showed no effects but 1,000 ppm produced vomiting and nausea which limited further testing at that concentration. ADN was not a genetic toxin, developmental toxin, reproductive toxin nor did it produce an increase in tumors in a 2‐yr drinking water study in rats. Human experience reports are limited to one accidental poisoning case and a few skin exposures resulting in transient irritation and inflammation. ADN is rapidly absorbed and excreted by mammals, and is metabolized to some extent although unchanged ADN is readily detected in urine, and does not bioaccumulate.

Final Report of the Amended Safety Assessment of PEG-5, -10, -16, -25, -30, and -40 Soy Sterol1

PEGs Soy Sterol are polyethylene glycol (PEG) derivatives of soybean oil sterols used in a variety of cosmetic formulations as surfactants and emulsifying agents, skin-conditioning agents, and cleansing and solubilizing agents. When the safety of these ingredients were first reviewed, the available data were insufficient to support safety. New data have since been received and the safety of these ingredients in cosmetics has been substantiated. Current concentration of use ranges from a low of 0.05% in makeup preparations to 2% in moisturizers and several other products. PEGs Soy Sterol are produced by the reaction of the soy sterol hydroxyl with ethylene oxide. In general, ethoxylated fatty acids can contain 1,4-dioxane as a byproduct of ethoxylation. The soy sterols include campesterol, stigmasterol, and beta-sitosterol. The distribution of sterols found in oils derived from common plants is similar, with beta-sitosterol comprising a major component. Impurities include sterol hydrocarbons and cholesterol (4% to 6%) and triterpine alcohols, keto-steroids, and other steroid-like substances (4% to 6%). No pesticide residues were detected. PEGS: Because PEGs are an underlying structure in PEGs Soy Sterols, the previous assessment of PEGs was considered. It is generally recognized that the PEG monomer, ethylene glycol, and certain of its monoalkyl ethers are reproductive and developmental toxins. Given the methods of manufacture of PEGs Soy Sterol, there is no likelihood of ethylene glycol or its alkyl ethers being present. Also, the soybean oil sterol ethers in this ingredient are chemically different from the ethylene glycol alkyl ethers of concern. PEGs are not carcinogenic, although sensitization and nephrotoxicity were observed in burn patients treated with a PEG-based cream. No evidence of systemic toxicity or sensitization was found in studies with intact skin. Plant Phytosterols: Intestinal absorption of ingested plant phytosterols is on the order of 5%, with 95% of the material entering the colon. Absorbed plant phytosterols are transported to the blood. Although there are some data suggesting that sulfates of beta-sitosterol can act as abortifacients in rats and rabbits, other studies of well-characterized plant phytosterols and phytosterol esters demonstrated no effect in an estrogen-binding study, a recombinant yeast assay for estrogen or estrogen-like activity, or a juvenile rat uterotrophic assay for estrogen or estrogen-like activity. In a two-generation reproduction study using rats, plant phytosterol esters in the diet had no effect on any parameter of reproduction or fertility. Subcutaneous injections of beta-sitosterol did reduce sperm concentrations and fertility in rats. Sitosterol inhibited tumor promoting activity of 12-O-tetradecanoylphorbol-13-acetate (TPA) in mice after initiation with 7,12-dimethylbenz[a]anthracene (DMBA), and reduced the tumors produced by N-methylnitrosourea in rats. Phytosterols were not genotoxic in several bacterial, mammalian, and in vitro assay systems. Phytosterols decreased epithelial cell proliferation in the colon of mice and rats, and were cytotoxic for human epidermoid carcinoma of the nasopharynx. PEGs Soy Sterols: The acute oral LD50 in rats of PEG-5-25 Soy Sterol was >10 g/kg. The acute dermal LD50 of a liquid eyeliner containing 2%PEG-5 Soy Sterol was >2 g/kg in rabbits. PEG-5-25 Soy Sterol was not a primary irritant in rabbits when applied undiluted. Undiluted PEG-5 Soy Sterol did not cause sensitization in guinea pigs. PEGs Soy Sterol did not produce ocular toxicity in rabbits. PEG-5 Soy Sterol was negative in the Ames mutagenicity test, with or without metabolic activation. PEG-5 Soy Sterol, at concentrations up to 2%in formulation, did not cause dermal or ocular irritation, dermal sensitization, or photosensitization in clinical studies. Because of the possible presence of 1,4-dioxane reaction product and unreacted ethylene oxide residues, it was considered necessary to use appropriate procedures to remove these from PEGs Soy Sterol before blending them into cosmetic formulations. Based on the systemic toxicity and sensitization seen with PEGs applied to damaged skin, it was recommended that PEGs Soy Sterol should not be used in cosmetic products applied to damaged skin. Although no dermal absorption data were available, oral studies demonstrate that phytosterols and phytosterol esters are not significantly absorbed and do not result in significant systemic exposure. Some small amounts did appear in the ovaries, however. This raises a concern about the potential presence of free phytosterols and beta-Sitosterol, which could have antiestrogenic, antiprogestational, gonadotrophic, antigonadotrophic, and antiandrogenic effects in PEG sterols. These concerns are alleviated by the extensive data showing that well-defined phytosterols and phytosterol esters are not estrogenic and do not pose a hazard to reproduction. Likewise, the absence of impurities in plant phytosterols and phytosterol esters and extensive data demonstrating the absence of any genotoxicity in bacterial and mammalian systems mitigate against the possibility of any carcinogenic effect with those same well-characterized materials. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the PEGs Soy Sterol are safe as used in cosmetic products.

Safety Assessment of Salicylic Acid, Butyloctyl Salicylate, Calcium Salicylate, C12–15 Alkyl Salicylate, Capryloyl Salicylic Acid, Hexyldodecyl Salicylate, Isocetyl Salicylate, Isodecyl Salicylate, Magnesium Salicylate, MEA-Salicylate, Ethylhexyl Salicylate, Potassium Salicylate, Methyl Salicylate, Myristyl Salicylate, Sodium Salicylate, TEA-Salicylate, and Tridecyl Salicylate

Safety Assessment of Salicylic Acid, Butyloctyl Salicylate, Calcium Salicylate, C12–15 Alkyl Salicylate, Capryloyl Salicylic Acid, Hexyldodecyl Salicylate, Isocetyl Salicylate, Isodecyl Salicylate, Magnesium Salicylate, MEA-Salicylate, Ethylhexyl Salicylate, Potassium Salicylate, Methyl Salicylate, Myristyl Salicylate, Sodium Salicylate, TEA-Salicylate, and Tridecyl Salicylate

The Registry of Cytotoxicity: Toxicity Testing in Cell Cultures to Predict Acute Toxicity (LD50) and to Reduce Testing in Animals

This is a translation of a report on the Registry of Cytotoxicity (RC), originally published in German in 1998. The report presented an advanced in vitro method, which can significantly reduce the number of animals needed for the toxicity testing of a broad range of compounds/xenobiotics. With the RC method, it was possible to predict the oral or intravenous acute toxicity (LD50)--which is a regulatory requirement for newly developed pharmaceuticals and industrial and household chemicals--from the cytotoxicity data (mean IC50 = IC50X) obtained with mammalian cells. The RC method can be used before the in vivo test, and it does not pose any additional harm or suffering to laboratory animals. The RC method is of broad practical use: it can be applied, for example, in the pharmaceutical industry or the chemical industry in regulatory testing or in research. It is ready for validation, and could then be incorporated into OECD guidelines, thus reducing the total number of animals needed for regulatory toxicity testing. The RC method is based on the comparison of the IC50X values and the LD50 values by using linear regression analysis. With the RC method, it was possible to predict, within a predefined dose range, the acute oral LD50 for 252 of 347 xenobiotics, and the intravenous LD50 for rats and/or mice for 117 of 150 xenobiotics. Comparative studies showed that these results are highly reproducible.

Inhibition and recovery of maternal and fetal cholinesterase enzymes following a single oral dose of chlorpyrifos in rats.

Pregnant Sprague-Dawley rats (14-18 days of gestation) were treated with a single dose of 50 mg/kg (61% of oral LD50 in female rats) of chlorpyrifos ( 0,0-diethyl- 0-3,5,6-trichloro-2-pyridyl phosphorothioate) by oral gavage. Animals treated on day 18 of gestation were sacrificed at 1, 2, 4, 12 h after dosing. Animals treated on days 17, 16, 15, and 14 of gestation were sacrificed at 24, 48, 72, and 96 h after dosing, respectively. Maternal and fetal brain acetylcholinesterase (AchE) and plasma butyrylcholinesterase (BuChE) activities were significantly inhibited 1 h after treatment. Activity of fetal brain AChE and plasma BuChE recovered faster than that of the maternal enzymes. Peak inhibition of maternal spinal cord AChE and BuChE activities occurred 2 h and 1 h after dosing, respectively. Maternal spinal cord BuChE activity was totally recovered by 96 h compared to the partial recovery of spinal cord AChE activity. Maternal liver BuChE activity was significantly decreased within 1 h of dosing. The individual molecular forms (10S and 4S) of maternal and fetal brain AChE and BuChE activities were significantly decreased 1 h after treatment. Recovery of both forms of fetal brain AChE activity was much faster than the maternal forms. Activity of the 10S form of maternal control brain AChE was significantly higher than in the fetus control. The rapid recovery of cholinesterase enzymes in the fetus is attributed to the de novo synthesis of AChE enzymes in the fetus compared to the mother.

Final Report On the Safety Assessment of Iodopropynyl Butylcarbamate (IPBC)

Iodopropynyl Butylcarbamate (IPBC) functions as a preservative in a wide variety of cosmetic formulations. Although concentrations as high as 0.1% have been reported, most applications appear to require this preservative at less than 0.0125%. IPBC readily penetrates through the skin. The average acute oral LD50 in rats is 1.47 g/kg. Rats fed IPBC for 4 weeks had increased liver weights and decreased plasma cholinesterase activity, and rats fed IPBC for 13 weeks had transient behavior alteration, increased liver weights, hepatocyte enlargement, stomach lesions, and decreased weight gain. Rats administered IPBC as dusts and liquid aerosols had labored breathing—lung edema, emphysema, and reddened lungs were observed after exposure. Dermal irritation, but no evidence of skin sensitization, was seen in animal studies. At concentrations of 0.5%, IPBC caused iritis and conjunctival irritation in rabbit eyes, but exposure to concentrations up to 0.015% produced only slight conjunctival redness. IPBC was not genotoxic, with or without metabolic activation. No evidence of carcinogenic potential was found in a 104-week chronic oral toxicity study using rats. Reductions in weight gain were observed, along with inflammation of the nonglandular stomach and lesions in the submaxillary salivary gland. In reproductive and developmental toxicity studies using rats and mice, IPBC had no significant effect on fertility, reproductive performance, or on the incidence of fetal malformations. IPBC was found to be mildly irritating, but not sensitizing in clinical testing. At concentrations up to 0.1%, IPBC was not comedogenic in clinical tests. Given the acute inhalation toxicity observed in animals, the potential for mild irritation, and the absence of any data on comedogenicity at concentrations higher than 0.1 % in clinical tests, the Expert Panel concluded that IPBC is safe as a cosmetic ingredient at concentrations ≤0.1 %, but that it should not be used in products intended to be aerosolized.

Final Report On the Safety Assessment of Polyvinyl Alcohol

Polyvinyl Alcohol is a synthetic alcohol used as a binder, film former, and viscosity increasing agent in a wide range of cosmetic formulations at concentrations up to 13%. Typical molecular weights range from 25,000 to 300,000. The acute oral LD50 in rats is reported to be >10 g/kg in one study and >21.5 g/kg in another. Dermal exposures of 5 and 13 weeks (the latter using 13% Polyvinyl Alcohol) produced no significant effects in rats. Various organ lesions and hypertension were noted in rats following repeated subcutaneous or intravenous dosing. Central nervous system depression and anemia, followed by renal damage, was seen in beagle dogs given daily intravenous injections of Polyvinyl Alcohol for a week. Several studies tested the carcinogenicity of subcutaneous implants of Polyvinyl Alcohol sponges or powder. Although the majority of these studies were positive, tumors were localized to the site of implantation. In another study in which Polyvinyl Alcohol was used as the vehicle for another agent and tested itself as the vehicle control, Polyvinyl Alcohol had no effect on the incidence of histiocytic sarcoma. Although no data were available assessing the reproductive or developmental toxicity, these endpoints were not considered to be likely with external exposure to this polymer. Polyvinyl Alcohol was not an ocular irritant in animal or clinical studies, nor was it a sensitizer. Some evidence of dermal irritation in animal and clinical studies was seen, but in the clinical studies it was not considered clinically significant. Based on these data, it was concluded that Polyvinyl Alcohol is safe as used in cosmetic formulations.

MEIC Evaluation of Acute Systemic Toxicity

The Multicenter Evaluation of In Vitro Cytotoxicity (MEIC) programme was set up to evaluate the relevance for human acute toxicity of in vitro cytotoxicity tests. At the end of the project in 1996, 29 laboratories had tested all 50 reference chemicals in 61 cytotoxicity assays. Five previous articles have presented the in vitro data and the human database to be used in the evaluation. This article presents three important parts of the final evaluation: a) a comparison of rat and mouse oral LD50 with human acute lethal doses for all 50 chemicals; b) a display of the correlations between IC50 (concentration causing 50% inhibition) values from all 61 assays and three independent sets of human acute lethal blood concentrations, i.e. clinical lethal concentrations, forensic lethal concentrations, and peak concentrations; and c) a series of comparisons between average IC50 values from ten human cell line 24-hour assays and human lethal blood concentrations. In the latter comparisons, results from correlations were linked with known human toxicity data for the chemicals, to provide an understanding of correlative results. This correlative/mechanistic approach had the double purpose of assessing the relevance of the in vitro cytotoxicities, and of testing a series of hypotheses connected with the basal cytotoxicity concept. The results of the studies were as follows. Rat LD50 predictions of human lethal dosage were only relatively good (R2= 0.61), while mouse LD50s gave a somewhat better prediction (R2= 0.65). Comparisons performed between IC50 values from the 61 assays and the human lethal peak concentrations demonstrated that human ceil line tests gave the best average results (R2= 0.64), while mammalian and fish cell tests correlated less well (R2= 0.52–0.58), followed by non-fish ecotoxicological tests (R2= 0.36). Most of the 61 assays underpredicted human toxicity for digoxin, malathion, carbon tetrachloride and atropine sulphate. In the correlative/mechanistic study, the 50 chemicals were first separated into three groups: A = fast-acting chemicals with a restricted passage across the blood–brain barrier; B = slow-acting chemicals with a restricted passage across the blood–brain barrier; and C = chemicals which cross the blood–brain barrier freely, while inducing a non-specific excitation/depression of the central nervous system (CNS). The IC50 values for chemicals in group C were divided by a factor of ten to compensate for a hypothetical extra vulnerability of the CNS to cytotoxicity. Finally, the average human cell line IC50 values (24-hour IC50 for groups A and C, and after 48-hour for group B) were compared with relevant human lethal blood concentrations (peak concentrations for groups A and C, and 48-hour concentrations for group B). As a result, in vitro toxicity and in vivo toxicity correlated very well for all groups (R2= 0.98, 0.82 and 0.85, respectively). No clear overprediction of human toxicity was made by the human cell tests. The human cell line tests underpredicted human toxicity for only four of the 50 chemicals. These outlier chemicals were digoxin, malathion, nicotine and atropine sulphate, all of which have a lethal action in man through interaction with specific target sites not usually found in cell lines. Potassium cyanide has a cellular human lethal action which cannot be measured by standard anaerobic cell lines. The good prediction of the human lethal whole-blood concentration of this chemical was not conclusive, i.e. was probably a “false good correlation”. Another two chemicals in group C resulted in “false good correlations”, i.e. paracetamol and paraquat. The comparisons thus indicated that human cell line cytotoxicities are relevant for the human acute lethal action for 43 of the 50 chemicals. The results strongly support the basal cytotoxicity concept, and further point to the non-specific CNS depression being the obligatory reaction of humans to cytotoxic concentrations of chemicals, provided that the chemicals are able to pass the blood–brain barrier.

Assessment of cocaethylene lethality in Long-Evans female and male rats.

Cocaethylene, the metabolite of cocaine produced only in the presence of alcohol, produces a number of pharmacological, physiological, and behavioral effects. It also has a range of toxicological consequences, the most severe being lethality. Given that the assessments of cocaethylene lethality have been limited to mice, the present study assessed the lethality of cocaethylene in rats. Further, because of within-species sex differences with its parent compound, cocaine, cocaethylene lethality was also examined in both females and males. Specifically, female and male rats were injected IP with 75, 87, 100, 115, and 133 mg/kg cocaethylene and observed over a 24-h period. Deaths were dose dependent and occurred within 30 min for both females and males. For females, the LD50 was 96 mg/kg; for males, the LD50 was 70 mg/kg. The percentage of rats displaying severe effects (i.e., seizure and death) increased with dose across all postinjection times. Further, these effects occurred earlier as dose increased. Differences in the LD50 for rats and mice, as well as the greater sensitivity to cocaethylene in male rats, are discussed.

Structure-activity relationships for rat and mouse LD50 of miscellaneous alcohols

Structure-activity relationships between acute toxicities of 95 alcohols to rat and mouse (oral LD50) and four special sub-structure factors, hydroxyl number, carbon atom number were examined by means of expert system method. The results showed that the expert system based QSAR model was excellent for classification for miscellaneous alcohols (only 9 of them were wrong classified). It was also used to predict the toxicity of other 25 alcohols, and the false prediction rate was only 12%.

Amended Final Report On the Safety Assessment of Dioctyl Sodium Sulfosuccinate

Dioctyl Sodium Sulfosuccinate is an anionic surfactant used in a wide variety of cosmetic formulations. In September 1994, the Cosmetic Ingredient Review (CIR) Expert Panel evaluated the ingredient to be safe up to 0.42% in cosmetic formulations. Since that time, CIR received a petition to re-open the safety assessment based on new clinical data. This amendment is a compilation of data contained in the original plus the data received in the petition; the latter appear at the end of this document. Studies conducted in the 1940's indicate that the oral LD50 in rats can be as low as 1.9 g/kg. Short-term subchronic and chronic animal studies of the same vintage found little toxicity at levels around 1% of the LD50 level. Inhalation studies likewise had few findings. Dioctyl Sodium Sulfosuccinate was minimally irritating to intact animal skin, but moderate to severely irritating to abraded skin. A concentration of 25% was a severe ocular irritant, but 10% produced little or no irritation. Mutagenesis tests were negative. A repeated insult patch test (RIPT) in 110 individuals produced no sensitization at a concentration of 5%. Erythema was noted during induction in a number of subjects at concentrations ≤5%. The CIR Expert Panel recognized that surfactants such as Dioctyl Sodium Sulfosuccinate would likely produce irritation under the conditions of a RIPT. The Panel cautioned that as the ingredient is a cumulative irritant, care should be taken to avoid irritancy in formulations intended for prolonged contact with the skin. The Panel concluded that Dioctyl Sodium Sulfosuccinate is safe for use in cosmetics.

Correlation of lethal doses of industrial chemicals between oral or intraperitoneal administration and inhalation exposure.

Correlations of lethal doses of industrial chemicals between oral or intraperitoneal administration and inhalation exposure in rats and mice were investigated. LC50 values for inhalation exposure and LD50 values for oral and intraperitoneal administration were obtained from the Registry of Toxic Effects of Chemical Substances. LC50 and LD50 values were plotted on ordinate and abscissa, respectively, using logarithmic scales. A correlation coefficient of r = 0.624 (n = 146, p < 0.001) was obtained for LC50 (ppm) and LD50 (mg/kg) values with oral administration (oral LD50) in rats. This correlation was improved by converting the units of LC50 from ppm to ppm h (cumulative dose), and by converting the units of LD50 from mg/kg to mmol/kg. The correlation coefficient was r = 0.742 when ppm*hr and mmol/kg were adopted for LC50 and LD50, respectively. A similar improvement in correlation coefficients by the same unit conversion was also observed between LC50 and LD50 with intraperitoneal (i.p.) administration (i.p. LD50) in rats. Correlations between LC50 and oral LD50 in mice were also improved by the same unit conversion. The correlations between LC50 and i.p. LD50 were higher than those between LC50 and oral LD50 both in rats and mice. In these correlations, coefficients obtained in rats were greater than corresponding coefficients in mice. We calculated equations to estimate LC50 values accompanied by confidence limits from oral or i.p. LD50 values.

ALTERATIONS OF MALE WISTAR RAT JEJUNUM INDUCED BY DODINE (n-DODECYLGUANIDINE ACETATE)

The effect of Dodine on the intestine was studied after a single administration of 1000 mg/kg, which corresponds to the LD50 in male Wistar rats. At this dose, a significant decrease in body weight was observed, accompanied by diarrhea, which may be associated with intestinal alterations. The chemical induced a significant reduction of the protein con tent and in sucrase activity in the jejunum. Morphological alterations included a significant decrease in crypt height and in villus length and depth. The intestinal modifications observed in animals after Dodine administration may explain the observed loss in body weight and diarrhea.

Antiinflammatory actions of Euphorbia splendens extract

Petroleum ether extract of the aerial parts of plant Euphorbia splendens (PEE) was screened for antiinflammatory activity using carrageenan induced oedema test in rats and mice as an acute and adjuvant arthritis as chronic models. Oral administration of PEE caused significant inhibition of oedema in these tests and produced inhibition of leucocyte migration and exudate volume in the affected tissues. The oral LD50 in both rats and mice was approximately 1250 mg/kg. © 1997 John Wiley & Sons, Ltd.

Antiinflammatory actions of Euphorbia splendens extract

Petroleum ether extract of the aerial parts of plant Euphorbia splendens (PEE) was screened for antiinflammatory activity using carrageenan induced oedema test in rats and mice as an acute and adjuvant arthritis as chronic models. Oral administration of PEE caused significant inhibition of oedema in these tests and produced inhibition of leucocyte migration and exudate volume in the affected tissues. The oral LD50 in both rats and mice was approximately 1250 mg/kg. © 1997 John Wiley & Sons, Ltd.

The pharmacological actions of polymethylene bistrimethylammonium salts. 1949.

The pharmacological properties of a series of polymethylene α-ωbistrimethylammonium iodides with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 18 carbon atoms in the polymethylene chain have been studied. The decane derivative (C10) causes neuromuscular block in the cat in doses of 30 μg./kg. intravenously, and is the most active member of the series in this respect. During such block, the excitability of nerve and muscle is retained, the effects of acetylcholine injected arterially are paralysed, and acetylcholine release by motor nerve terminals is not prevented. Tetanization of the motor nerve or injection of acetylcholine or potassium neither diminishes nor deepens the block. A phase of potentiation of the muscle twitch, fasciculations of the muscle, and repetitive responses to single nerve volleys precedes the block. During a partial block, tetanization of the muscle leads to a well-sustained contraction. In the cat, profound neuromuscular block of the tibialis muscle may be caused by C10, without paralysis of respiratory muscles. With d-tubocurarine chloride respiratory paralysis accompanies or may precede paralysis of tibialis. C10 is 50–100 times less active by mouth than by intravenous injection. Its activity in cats anaesthetized with chloralose or pentothal is similar to that in the unanaesthetized cat; but ether appears to antagonize it slightly. Sensitivity to C10 varies greatly with species: in order of decreasing sensitivity, the series is cat-man - rabbit - monkey - mouse - rat. For d-tubocurarine chloride by the same tests, the variation in sensitivity is much smaller and decreases: rat-mouse-rabbit-cat. The action of C10 is not antagonized by anticholinesterases. The pentane and hexane homologues (C5, C6) are effective antagonists; the antagonism appears to be by competitive inhibition. Previous administration of d-tubocurarine chloride also reduces the effectiveness of C10. C10 and its neighbours elicit a contracture of the frog's rectus abdominis muscle, and do not antagonize the contracture elicited by acetylcholine. C5 and C6 do not elicit such a contracture, but antagonize the actions both of C10 and of acetylcholine. C10 can also elicit a twitch of cat's tibialis muscle if a small dose is given by close arterial injection. Members of the series, particularly C5 and C6, are able to block ganglionic transmission. Higher members possess a weak anticholinesterase action, which is more active against “true” cholinesterase than against “pseudo” cholinesterase. They also possess a weak muscarine-like action, a weak power of releasing histamine, and a feeble antibacterial action. No significant atropine-like action, or ability to stimulate autonomic ganglia, was detected. With the exception of C18, members of the series display negligible activity in depressing the surface tension of water. The pharmacological properties of the series have been related to the length of the polymethylene chain. This reveals four features: (1) a sharp maximum for potency in ganglionic block at C5–C6; (2) a sharp maximum for potency in neuromuscular block at C10; (3) a less well-defined maximum for muscarine-like activity, stimulation of frog's rectus, and anticholinesterase activity about C12; (4) a rise in antibacterial activity and surface activity beginning about C12 and still increasing at C18. The significance of the species difference, of the competitive antagonism of C5 for C10, of the variation of activity with length of polymethylene chain, and of the differences between C10 and d-tubocurarine chloride is discussed. It is a pleasure to express our indebtedness to Dr. Harold King for his interest and guidance throughout this investigation, and to our colleagues for many fruitful discussions and criticisms. We are also indebted to Dr. T. S. Work for advice on determining anticholinesterase activity, to Miss Bashford for assistance in these determinations, and to Dr. J. Niven for the histological examinations.

Evaluation of the Role of Formulation on Parathion Toxicity

The influence of the vehicle on the toxicity of parathion was evaluated by determining the oral and dermal LD50in rats. The assessment of dermal absorption was performed by measuring the inhibition of plasma cholinesterase activity. The test vehicles were arol and xylene. The data obtained indicated that the acute oral and dermal toxicities are higher in xylene than in arol, but no differences were observed on plasma cholinesterase activity.

Final Report on the Safety Assessment of Methyldibromo Glutaronitrile

The halogen compound Methyldibromo Glutaronitrile is used in a wide variety of cosmetics as a preservative. Concentrations in cosmetic formulations reportedly range from 0.0075 to 0.06%. The oral LD50 in rats is 640 mg/kg. Dogs on a diet of 4,000 ppm Methyldibromo Glutaronitrile for 13 weeks developed thyroid hyperplasia; those on a diet of 167 ppm exhibited no hyperplasia, although the thyroid glands were enlarged. Application of Methyldibromo Glutaronitrile at a level of 4.0 g/kg to the skin of rats for 21 days produced severe irritation. A concentration of 0.025% applied to the skin of rabbits in a 28-day dermal toxicity study resulted in only slight to moderate irritation. No evidence of sensitization was found in guinea pig studies, nor was photosensitization reported in mouse studies. No reproductive or developmental toxicity was noted in two rat studies. Methyldibromo Glutaronitrile was not mutagenic in a series of mammalian system tests. Clinical data using repeat insult patch testing (HRIPT) methods indicated that concentrations as low as 0.025% produced a positive reaction in a few individuals. To limit the possibility that formulations containing this ingredient will lead to sensitization, it was concluded that leave-on formulations should contain 0.025% Methyldibromo Glutaronitrile. Rinse-off formulations, because the duration of exposure is much less, are considered safe as currently used

Final Report on Ethyl Methacrylate

Ethyl Methacrylate is the ester of ethyl alcohol and methacrylic acid used as the major structural monomer of artificial fingernail formulations that are cross-linked with one or more multifunctional methacrylates. Ethyl methacrylate monomer is polymerized rapidly and very little free monomer is available even during filing of the fingernails. The oral LD50 for rats ranged from 12.7 to 18.14 g/kg, with lesions in the respiratory system and hemoglobinuria observed in treated animals. Ocular, nasal, and respiratory tract irritation was observed in acute inhalation tests using rats. Very little toxicity was seen in subchronic studies using rabbits. Ethyl Methacrylate caused irritation and vehicle dependent sensitization in animals, but no photosensitization. Evidence of embryotoxic and teratogenic effects were observed in pregnant rats after intraperitoneal injection of Ethyl Methacrylate at a range of concentrations. Both positive and negative mutagenicity test data were found. Clinical testing showed little evidence of irritation, although case studies report allergic contact dermatitis as a result of exposure to Ethyl Methacrylate and related methacrylates with application of artificial fingernails. Occupational contact dermatitis from acrylates and methacrylates are also reported, with some evidence for cross-reactivity between the two chemical classes. Based on the sensitizing potential of this ingredient the CIR Expert Panel recommended that fingernail enhancement formulations with Ethyl Methacrylate be applied only by trained individuals and that the ingredient not be used in products intended for retail sale (currently, these products are believed to be sold only for application by a trained individual). Because of the low likelihood of significant exposure if such formulations are applied properly, the Expert Panel concluded that the ingredient is safe as used, with the caveat that skin contact should be avoided.

Final Report on the Safety Assessment of Polyoxymethylene Urea

Polyoxymethylene Urea is a variable molecular weight polymer formed in stages from the condensation reaction of urea with formaldehyde. It is used in a wide range of cosmetic formulations as a bulking agent and to form the outer shell of microcapsules. Because of the nature of the polymerization process, residual formaldehyde is present at levels typically between 17 and 30 ppm. Polyoxymethylene Urea shows low toxicity. The oral LD50 in rats was 10 g/kg for the bulk material and 20 g/kg when the microcapsule form was used. Polyoxymethylene Urea was a mild skin irritant and caused mild, transient ocular irritation in rabbits. Ames tests were negative for mutagenesis. Clinical data showed no irritation or sensitization. On the basis of the data, it is concluded that Polyoxymethylene Urea is safe for use as a cosmetic ingredient. A previous determination, however, that the concentration of free formaldehyde in cosmetic formulations should not exceed 0.2% was considered appropriate for this ingredient as well. Likewise, the previous finding that the safety of formaldehyde was not ensured in cosmetic products intended to be aerosolized is extended to this ingredient.