Postnatal developmental alterations following prenatal exposure to the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether: a dose response evaluation in the mouse

Although nitrofen, 2,4-dichlorophenyl-p-nitrophenyl ether, is a relatively nontoxic herbicide, prenatal exposure to doses considerably less than the LD50 value for adult rats and mice produces numerous developmental defects that become apparent as the animals mature. In the present study postnatal development was observed following prenatal exposure during Days 7 to 17 of gestation at doses of 0, 6.25, 12.5, 25, 50, 100, 150, and 200 mg/kg/day. These doses did not cause maternal toxicity as indicated by the viability of the dams or maternal weight gain during pregnancy. By 3 days of age all pups in the two highest dose groups were dead and 50% had died in the 100 mg/kg/day dose group. Some of the dead and moribund pups from the 200 mg/kg/day exposure group necropsied at three days of age had cleft palate (15%) or diaphragmatic hernia (6%). In addition, about 22% of the pups at 200 mg/kg/day developed a distended abdomen from gasping and swallowing air. These pups did not suckle and eventually died. Body weights of offspring were reduced at birth in the 150 and 200 mg/kg/day groups and at 3 days of age in the 100 mg/kg/day group. Growth rates were subsequently retarded at 12.5, 25, 50, and 100 mg/kg. The Harderian glands were reduced or absent in 97, 65, and 4% of the mice in the 100, 50, and 25 mg/kg dosage groups, respectively, and the gland weights were reduced at all dosages, including the lowest dose of 6.25 mg/kg/day. Weights of other organs including lung and liver (at 6.25 and above), seminal vesicle (at 12.5 and above), and testes (at 100 mg/kg/day) were also reduced by prenatal nitrofen exposure. In addition, prenatal treatment with nitrofen produced functional deficits of the reproductive system; puberty was delayed in females and litter sizes were reduced at 50 and 100 mg/kg/day. A cross-fostering experiment with 100 mg/kg/day of nitrofen demonstrated that the effects noted in the present study were produced solely by prenatal exposure; pups exposed to nitrofen in the milk alone as a consequence of any accumulation of nitrofen in the dam during gestation were unaffected.     

The pharmacokinetics and macromolecular interactions of perchloroethylene in mice and rats as related to oncogenicity

The pharmacokinetic and macromolecular interactions of perchloroethylene were evaluated in B₆C₃F₁ mice and Sprague-Dawley rats in an attempt to explain, mechanistically, the sensitivity of the mouse and the resistance of the rat to perchloroethylene-induced hepatocellular carcinoma. When compared to rats, mice were found to metabolize 8.5 and 1.6 times more perchloroethylene per kilogram of body weight following inhalation of 10 ppm or a single oral dose of 500 mg/kg perchloro[¹⁴C]ethylene, respectively. Since the initial metabolism of perchloroethylene is an activation process, the increased extent of metabolism in the mouse resulted in a greater extent of irreversible binding of radioactivity in hepatic macromolecules of the mouse compared to that in the rat after inhalation of 10 or 600 ppm or a single oral dose of 500 mg/kg perchloro[¹⁴C]ethylene. Repeated oral administration of perchloroethylene for 11 days resulted in histopathological changes in the liver of mice at doses as low as 100 mg/kg/day, while minimal treatment-related effects were observed in the liver of rats only at the 1000 mg/kg/day level. Approximately a twofold increase in hepatic DNA synthesis, indicative of hepatic regeneration, was observed in mice but not in rats after repeated oral administration of perchloroethylene at dose levels which are tumorigenic to mice in lifetime studies. The absence of any pronouced direct interaction of perchloroethylene with hepatic DNA in mice at times of peak hepatic macromolecular binding suggests that hepatic tumors are induced in B₆C₃F₁ mice by recurrent cytotoxicity which enhances the spontaneous incidence of liver tumors in this highly susceptible strain of mouse. The implication of these results for hazard assessment is that recurrent tissue damage is necessary for tumors to be induced. Thus, levels of perchloroethylene which do not induce organ toxicity are not likely to pose a carcinogenic risk to man.     

Nonclinical safety assessment of Efinaconazole Solution (10%) for onychomycosis treatment

Efinaconazole is a triazole developed as a 10% solution for topical treatment of onychomycosis, a common fungal nail infection. Efinaconazole solution and topical formulation vehicle administered dermally to mice (13 weeks), rats (6 months) and minipigs (9 months) produced transient erythema, minimal to modest hyperkeratosis, and mild microscopic skin inflammation. The liver was the target organ of systemic toxicity; reversible, minimal to moderate vacuolated changes were noted in the rat dermal study at 15 and 50 mg/kg/day. No systemic toxicity was observed in mice and minipigs, at approximate high dermal doses of 930 and 170 mg/kg/day, respectively. Daily subcutaneous injection of propylene glycol vehicle or efinaconazole to rats for 6 months produced severe local inflammation and systemic spread, evidenced by peritoneal adhesions, spinal cord necrosis and urinary tract disease. Mortalities occurred in all groups but were increased at the high dose (30 or 40 mg/kg/day), suggesting that vehicle effects were exacerbated by efinaconazole. Efinaconazole was not carcinogenic in a 2-year mouse dermal study and was not genotoxic. Exposure-based safety margins at the NOAEL were 70–698 relative to onychomycosis patients. In conclusion, efinaconazole demonstrated low/moderate toxicity, consistent with other azole antifungals, and high safety margins for topical onychomycosis therapy.     

The toxicology of the schistosomicidal agent oxamniquine

Oxamniquine displayed low acute toxicity in mice, hamsters, and rabbits. In rats, however, oxamniquine was much more toxic, the female being 8–10 times more sensitive than the male; single doses elicited an idiosyncratic sex-linked hepatic necrosis and bile duct proliferation. Dogs given repeated oral doses of 20 or 30 mg/kg/day for 5 successive days every 4 weeks for 11 months showed neurological disturbances of short duration, which tended gradually to increase in severity from one dosage period to the next; no histopathological correlate could be found. In chronic studies in mice (18 months) and hamsters (19 months) with intermittent dosage regimens relevant to likely usage in man, no evidence of carcinogenicity potential was observed at dose levels up to 150 mg/kg. Oxamniquine displayed no maternal toxicity or teratogenicity in mice and rabbits, and only slight embryotoxicity after high oral doses.     

Evaluation of the safety of mixed tocopheryl phosphates (MTP) -- a formulation of alpha-tocopheryl phosphate plus alpha-di-tocopheryl phosphate.

The safety of a formulation of mixed tocopheryl phosphates, (MTP) was evaluated in a series of toxicological tests in vivo using rats, mice and rabbits and in vitro using bacterial and mammalian cell cultures. The tests conducted included an oral LD(50) study, three 28-day oral repeat-dose studies, two dermal toxicity tests, an ocular irritation test, mutagenic potential tests, and chromosomal aberrations tests. MTP consists of mono alpha-tocopheryl phosphate (TP) and di-tocopheryl phosphate (T(2)P) and is intended for use as a dietary supplement and for dermal applications in humans and animals. The dermal and oral LD(50) values of MTP were determined to be >1130 mg/kg bw (918 mg tocopherol equivalents/kg bw) in rabbits and rats, respectively. MTP was not a dermal or eye irritant in rabbits and showed no allergenic potential in mice. In the mutagenicity and genotoxicity studies, MTP did not increased the number of revertants in Salmonella typhimurium or Escherichia coli and did not induce chromosomal aberrations in cultured Chinese hamster ovary (CHO) cells. When administered daily for 28 days by gavage at doses up to 955 mg/kg bw/day (780 mg tocopherol equivalents/kg bw/day), MTP produced no consistent, dose-dependent adverse effects in rats.     

Toxicological evaluation of ammonium 4,8-dioxa-3H-perfluorononanoate,a new emulsifier to replace ammonium perfluorooctanoate in fluoropolymer manufacturing

Ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA) was developed to replace ammonium perfluorooctanoate (APFO) as an emulsifier in the manufacture of fluoropolymers. The toxicity of ADONA was evaluated in acute and repeat-dose studies of up to 90-days duration, and in eye and skin irritation, dermal sensitization, genotoxicity, and developmental toxicity studies. ADONA was also evaluated as a peroxisome proliferator-activated receptor alpha (PPARα) agonist in rats. ADONA was moderately toxic orally and practically non-toxic dermally in acute studies in rats. It was a mild skin irritant and a moderate to severe eye irritant in rabbits. It was a weak dermal sensitizer in local lymph node assays in mice. ADONA was not genotoxic based on the weight of evidence from five assays. It was not developmentally toxic in rats except at maternally toxic doses. ADONA was a possible PPARα agonist in male rats. The liver was the primary target organ in male rats and the kidney was the primary target organ in female rats. NOAELs in 28- and 90-day oral studies in rats were 10 mg/kg/day for males and 100 mg/kg/day for females. These findings demonstrate that the toxicity profile for ADONA is acceptable for its intended use and is superior to that of APFO.     

In vivo acute toxicological studies of an antioxidant extract from Mangifera indica L. (Vimang)

Mango (Mangifera indica L.) stem bark aqueous extract (MSBE) is a natural product with antioxidant, anti-inflammatory, analgesic, and immunomodulatory effects. Its formulations (e.g., tablets, capsules, syrup, vaginal oval, and suppositories) are known by the brand name of Vimang®. In view of the ethnomedical, preclinical, and clinical uses of this extract and the necessity to assess its possible toxicological effect on man, a toxicological analysis of a standard extract is reported in this paper. Acute toxicity was evaluated in mice and rats by oral, dermal, and intraperitoneal (i.p.) administration. The extract, by oral or dermal administration, showed no lethality at the limit doses of 2,000 mg/kg body weight and no adverse effects were found. Deaths occurred with the i.p. administration at 200, but not 20 mg/kg in mice. MSBE was also studied on irritant tests in rabbits, and the results showed that it was nonirritating on skin, ocular, or rectal mucosa. The extract had minimal irritancy following vaginal application.     

Subacute oral and dermal toxicity of tert-butyl hydroperoxide in Fischer F344/N rats and B6C3F1 mice

Tert-butyl hydroperoxide (TBHP) is a catalyst frequently used in oxidation and sulfonation reactions in the plastics industry. Since the toxicological evaluation of TBHP remains unknown, the National Toxicology Program (NTP) designed studies to characterize and compare TBHP toxicity by the dermal and oral (gavage) routes in male and female Fischer 344 rats and B6C3F1 mice in 14-day exposures. Rats and mice were administered TBHP at 22, 44, 88, 176 or 352 mg/kg in 0.5% aqueous methylcellulose for the gavage studies. In the dermal studies, mice were administered the same doses as above, while rats were administered four doses (22, 44, 88, 176 mg/kg) in 50% aqueous acetone. Results from the gavage studies revealed treatment-related decreases in survival in male rats and body weights in both male and female rats in the 352 mg/kg group. Clinical signs included post-treatment lethargy, thinness, abnormal breathing, ruffled fur, and/or ataxia which occurred sporadically. The male mice showed a statistically significant decrease in body weight in the 44, 88, 176, and 352 mg/kg groups. The major target organs of toxicity were the forestomach in male and female rats and mice, and the esophagus in male and female rats and in male mice. In addition, there was an increase in the absolute and relative liver weight in female mice with hepatocellular hypertrophy in the top-dose group only. Results from spin trapping experiments revealed the presence of electron paramagnetic resonance signals from radical adducts in the blood and organic extracts of the liver and kidneys of rats treated by gavage with 176 mg/kg TBHP, suggesting the involvement of free- radical generation. The no observed adverse effect level (NOAEL) was considered to be 22 mg/kg in rats and male mice, and 44 mg/kg in female mice. In the dermal studies, there was no effect on survival, body weight, or organ weights in either rats or mice. TBHP administration at the site of application resulted in dermal irritation, hyperkeratosis, hyperplasia, and/or inflammation of the epidermis and inflammation of the dermis at 176 mg/kg and above in male and female rats. Dermal irritation at the site of application was noted in all the mice exposed to 352 mg/kg TBHP. Histopathological lesions in the epidermis and dermis were seen in the 88–352 mg/kg males and in the 176–352 mg/kg females. The NOAEL was found to be 88 mg/kg for male rats and female mice, and 44 mg/kg for female rats and male mice. In conclusion, these studies demonstrate that TBHP is metabolized to free radicals and is a contact irritant affecting skin by the dermal route of exposure, and forestomach and esophagus by oral administration. There was no evidence of systemic absorption by the dermal route of exposure based on lack of pathological findings (Supported by National Institute of Environmental Health Sciences Contract No. N01-ES-65406).     

Subacute oral and dermal toxicity of tert-butyl hydroperoxide in Fischer F344/N rats and B6C3F1 mice

Tert-butyl hydroperoxide (TBHP) is a catalyst frequently used in oxidation and sulfonation reactions in the plastics industry. Since the toxicological evaluation of TBHP remains unknown, the National Toxicology Program (NTP) designed studies to characterize and compare TBHP toxicity by the dermal and oral (gavage) routes in male and female Fischer 344 rats and B6C3F1 mice in 14-day exposures. Rats and mice were administered TBHP at 22, 44, 88, 176 or 352 mg/kg in 0.5% aqueous methylcellulose for the gavage studies. In the dermal studies, mice were administered the same doses as above, while rats were administered four doses (22, 44, 88, 176 mg/kg) in 50% aqueous acetone. Results from the gavage studies revealed treatment-related decreases in survival in male rats and body weights in both male and female rats in the 352 mg/kg group. Clinical signs included post-treatment lethargy, thinness, abnormal breathing, ruffled fur, and/or ataxia which occurred sporadically. The male mice showed a statistically significant decrease in body weight in the 44, 88, 176, and 352 mg/kg groups. The major target organs of toxicity were the forestomach in male and female rats and mice, and the esophagus in male and female rats and in male mice. In addition, there was an increase in the absolute and relative liver weight in female mice with hepatocellular hypertrophy in the top-dose group only. Results from spin trapping experiments revealed the presence of electron paramagnetic resonance signals from radical adducts in the blood and organic extracts of the liver and kidneys of rats treated by gavage with 176 mg/kg TBHP, suggesting the involvement of free- radical generation. The no observed adverse effect level (NOAEL) was considered to be 22 mg/kg in rats and male mice, and 44 mg/kg in female mice. In the dermal studies, there was no effect on survival, body weight, or organ weights in either rats or mice. TBHP administration at the site of application resulted in dermal irritation, hyperkeratosis, hyperplasia, and/or inflammation of the epidermis and inflammation of the dermis at 176 mg/kg and above in male and female rats. Dermal irritation at the site of application was noted in all the mice exposed to 352 mg/kg TBHP. Histopathological lesions in the epidermis and dermis were seen in the 88-352 mg/kg males and in the 176-352 mg/kg females. The NOAEL was found to be 88 mg/kg for male rats and female mice, and 44 mg/kg for female rats and male mice. In conclusion, these studies demonstrate that TBHP is metabolized to free radicals and is a contact irritant affecting skin by the dermal route of exposure, and forestomach and esophagus by oral administration. There was no evidence of systemic absorption by the dermal route of exposure based on lack of pathological findings (Supported by National Institute of Environmental Health Sciences Contract No. N01-ES-65406).     

The oral and dermal toxicity of hexachlorophene in rats

The single oral LD50 of hexachlorophene in adult male Sherman strain rats was 66 mg/kg, in females 56 mg/kg; in famale weanling rats the single oral LD50 was 120 mg/kg. The acute dermal toxicity was low. The iv LD50 in adult male rats was 7.5 mg/kg. Rats fed 500 ppm of hexachlorophene for 98 days developed leg weakness in 12–19 days. At sacrifice, after 98 days' exposure, status spongiosus was present throughout the white matter of the brain. Rats fed 100 ppm of hexachlorophene for 98 days did not develop leg weakness, but in 50% of the brains focal areas of status spongiosus were observed in the white matter. Rats fed 20 and 100 ppm of hexachlorophene for 258 days did not develop leg weakness. The brains of rats fed 20 ppm were normal, while the brains of some rats fed 100 ppm showed focal vacuolization of the white matter. One hundred parts per million reduced the survival of pups in the F₁ generation. This was statistically significant in the F_1b generation. The F₂ generation litters tended to be smaller. Reproduction was normal in rats fed 20 ppm or given hexachlorophene by oral intubation at doses as high as 10 mg/kg/day during day 7 to day 15 of pregnancy. Dermal application of 12 mg/kg/day of hexachlorophene for 30 days produced no microscopic changes in the brain and produced only erythema and desquamation of the treated skin. Doses of 24 and 48 mg/kg/day produced ulceration of the treated skin and status spongiosus of the entire white matter of the brain in some rats.     

Oral and dermal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces cutaneous papillomas and squamous cell carcinomas in female hemizygous Tg.AC transgenic mice.

Tg.AC mice develop epidermal papillomas in response to treatment with dermally applied nongenotoxic and complete carcinogens. The persistent environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a multi-site rodent carcinogen and tumor promoter that induces the formation of papillomas in Tg.AC mice. To examine the dose-response relationship and compare dermal and oral routes of exposure for TCDD-induced skin papillomas, female Tg.AC mice were exposed dermally to average daily doses of 0, 2.1, 7.3, 15, 33, 52, 71, 152, and 326 ng TCDD/kg/day or 0, 75, 321, and 893 ng TCDD/kg body weight by gavage for 26 weeks. The incidence of cutaneous papillomas was increased in a dose-dependent manner, and tumors developed earlier with higher exposure to TCDD regardless of route of administration. Increased incidences of cutaneous squamous cell carcinomas were observed in mice exposed to dermal (> or =52 ng/kg) and oral (893 ng/kg) TCDD. Higher gavage doses than dermal exposure doses were required to induce papillomas and squamous cell carcinomas. Despite a linear correlation between administered dose and terminal skin concentrations, the incidence of tumor formation was lower in the gavage study than in the dermal study with respect to mean terminal skin TCDD concentrations. These studies demonstrate that, although Tg.AC mice are less responsive to TCDD by gavage than by dermal exposure, the induction of skin neoplasms is a response to systemic exposure and not solely a local response at the site of dermal application. Differences in response between the routes of exposure may reflect pharmacokinetic differences in the delivery of TCDD to the skin over the duration of the study.     

Safety studies of pseudo-ceramide SLE66: Acute and short-term toxicity

Topical application of ceramides is reported to improve the structure and texture of the skin. Synthetic pseudo-cermaide, SLE66 has been shown to reduce dryness/scaling/itching of human skin. Although efficacy of topically applied ceramides and their analogs has been investigated to some extent, safety information is scarce. The objective of the present investigation was to evaluate potential adverse effects of SLE66. The oral LD₅₀ of SLE66 in rats and mice was >5000 mg/kg, while dermal LD₅₀ in rats was >2000 mg/kg. In animal and human studies, SLE66 did not cause skin irritation or sensitization. SLE66 does not possess phototoxicity or photosensitization potentials. Instillation of SLE66 into rabbit eye elicited transient conjunctival irritation. In 28 day repeat-dose studies, administration of SLE66 via gavage (daily) or by dermal application (five days/week) to Sprague Dawley rats at levels up to 1000 mg/kg/day did not cause mortality or morbidity. Compared to the controls, the clinical condition of the animals, body weights, feed consumption, hematology, clinical chemistry, organ weights, and gross necropsy findings were unaffected by oral or dermal administration of SLE66. The no-observed-adverse-effect level (NOAEL) for systemic toxicity following oral or dermal administration of SLE66 was 1000 mg/kg/day (the highest level tested).     

Repeated dose toxicity and developmental toxicity of diisopropanolamine to rats.

The repeated dose oral and dermal toxicity of diisopropanolamine (DIPA) was evaluated in rats and compared to the reported toxicity of the related secondary alcohol amine, diethanolamine (DEA). Fischer 344/DuCrl rats were given up to 750 mg/kg/day by dermal application, 5 days/week, for 4 weeks; or up to 1,000 mg DIPA/kg/day by drinking water for 13 weeks to evaluate potential toxic effects. Time-mated female CRL:CD(SD) rats were given up to 1,000 mg/kg/day by gavage on gestation days (GD) 6-20 for evaluation of maternal and fetal effects. In the dermal toxicity study, no adverse treatment-related in-life effects other than mild irritation at the site of dermal application at >or= 500 mg/kg/day were observed. There were no systemic effects in rats given up to 750 mg/kg/day. In the subchronic oral toxicity study, the most significant effects were an increase in absolute and relative kidney weights, unaccompanied by histopathologic changes, at >or= 500 mg/kg/day DIPA. The latter effect was ameliorated following a 4-week recovery period. In the developmental toxicity study, there were no maternal or developmental effects at any dose level evaluated. The toxicity of DIPA contrasts with that of DEA which has been shown to affect a number of organ systems when repeatedly administered orally or dermally at similar or lower dosages.     

Safety studies on epigallocatechin gallate (EGCG) preparations. Part 2: dermal, acute and short-term toxicity studies.

Green tea extract and its principal active ingredient, epigallocatechin gallate (EGCG), are gaining attention and increased usage due to their healthful properties. Despite the increasing demand for these products, few studies have examined their safety. The toxicity of purified green tea extracts containing high concentrations of EGCG have been evaluated in a series of studies in order to define the safety of Teavigo, a high-concentration EGCG extract produced by the same novel method. Topical EGCG preparations caused minor dermal irritation in rats and guinea pigs, but not rabbits, and was a moderate dermal sensitizing agent in the guinea pig maximization test. A rabbit eye irritation test produced a strong enough response to not warrant any further testing in this assay. An oral dose delivering 2000 mg EGCG preparation/kg was lethal to rats; whereas, a dose of 200 mg EGCG/kg induced no toxicity. The dietary administration of EGCG preparation to rats for 13 weeks was not toxic at doses up to 500 mg/kg/day. Similarly, no adverse effects were noted when 500 mg EGCG preparation/kg/day was administered to pre-fed dogs in divided doses. This dose caused morbidity when administered to fasted dogs as a single bolus dose, although this model was considered an unrealistic comparison to the human condition. From these studies a no-observed adverse effect level of 500 mg EGCG preparation/kg/day was established.     

Studies on the prenatal toxicity of N,N-dimethylformamide in mice, rats and rabbits.

Prenatal toxicity studies with N,N-dimethylformamide (DMF) in rabbits, rats and mice were carried out using the oral (gavage), dermal, inhalation and ip injection routes of administration. Administration of DMF by gavage led to an increase in malformations in rats and mice in the absence of overt maternal toxicity. The lowest-observable-effect level was 182 mg/kg body weight/day in mice and 166 mg/kg body weight/day in rats. After dermal administration a dose-dependent incidence of teratogenicity was observed in rats at 94-944 mg/kg/body weight/day in the absence of overt maternal toxicity. In rabbits dermal administration led to a steeper increase in the dose-response relationship and at 400 mg/kg body weight/day to a clear teratogenic effect in the presence of slight maternal toxicity. The 200 mg/kg body weight/day dose appeared to be the no-adverse-effect level. Inhalation in rats caused foetotoxicity and embryolethality at 287 ppm. A clear teratogenic effect was shown in rabbits at 450 ppm and a marginal effect at 150 ppm. The no-effect level for does and foetuses was 50 ppm. Ip injection in mice caused clear teratogenicity at 944 mg/kg body weight/day and slight embryotoxicity at 378 mg/kg body weight/day. The rabbit appears to be more sensitive than the rat to DMF-related prenatal toxicity and should, therefore, be used as the basis for the evaluation of teratogenic risk in humans.     

The acute and subchronic effects of ketoconazole on hepatic microsomal monooxygenases in the rat

Female adult Wistar rats were treated with single or repeated doses of ketoconazole ranging from 10 mg/kg to 100 mg/kg. Single dose treatment produced inhibition of hepatic microsomal ethoxyresorufin O-deethylation (EROD) and aldrin epoxidation (AE) 2 hr after oral dosing. Twenty-four hours after a single dose, inhibition was still demonstrable after the low dose of 10 mg/kg, but at higher doses increased microsomal activity was apparent. After 7 days repeated dosing liver weight and microsomal protein content were increased in a dose-dependent fashion. EROD and AE were induced at all doses after repeated treatment when the increase in liver size was considered. These effects were seen at doses within the antimycotic therapeutic range and add support to the suggestion that reported drug interactions with ketoconazole in man are due to the effects of this drug on hepatic microsomal activity.     

Maleic acid dimethylester: evaluation of dermal toxicity and genotoxicity

Maleic acid dimethylester (MAD) was investigated in acute and subacute dermal toxicity studies, for sensitization potential, and for in vivo and in vitro genotoxicity. The acute dermal toxicity in rats was low (LD50 greater than 2000 mg/kg body weight). Only local effects, erythema and necrosis, occurred at the site of application. Corresponding dose-related effects were observed in a 28-day repeated dermal toxicity study in rats. Treatment-related systemic alterations were observed in feed consumption, body weights, haematology and clinical chemistry at 170 and 500 mg MAD/kg body weight. Based on the results of this study, the no-toxic-effect level of MAD was considered to be 60 mg/kg body weight/day. However, slight dermal irritative effects were also present at the lowest dose level (60 mg/kg body weight). The primary skin irritation test in rabbits showed only slight erythema and oedema. The results of the maximization test in guinea-pigs indicated a clear sensitizing potential of MAD. In the Ames test, with five strains of Salmonella typhimurium, MAD was not mutagenic up to the highest dose level of 5000 micrograms/plate. In the micronucleus test, in which mice were given 1000 mg MAD/kg body weight by gavage the compound revealed no clastogenic effects.     

The Evaluation of the Developmental Toxicity of Hydrochlorothiazide in Mice and Rats

Timed-pregnant CD-1 outbred albino Swiss mice and CD Sprague-Dawleyrats were administered hydrochlorothiazide (HCTZ, USP) in cornoil by gavage during major organogenesis, Gestational Days (GD)6 through 15. The doses administered were 0, 300, 1000, or 3000mg/kg/day for mice and 0, 100, 300, or 1000 mg/kg/day for rats.Maternal clinical status was monitored daily during treatment.At termination (GD 17, mice; GD 20, rats), confirmed pregnantfemales (20–27 per group, mice; 36–39 per group,rats) were evaluated for clinical status and gestational outcome;each live fetus was examined for external, visceral, and skeletalmalformations. In mice, no maternal mortality was observed.However, clinical signs including dehydration, pioerection,lethargy, and single-day weight loss appeared to be doserelated.HCTZ had no effect on maternal weight gain or water consumption,gravid uterine weight, relative maternal liver weight, or relativematernal kidney weight. There was no definitive evidence ofembryotoxicity or fetal toxicity for mice on GD 17. Thus, theno observed adverse effect level (NOAEL) for both maternal anddevelopmental toxicity was 3000 mg/kg/day. In rats, HCTZ hadno effect on maternal survival, clinical signs, or water consumption.Clinical signs were not dose-related. Maternal weight gain duringtreatment was depressed at 1000 mg/kg/day. Gravid uterine weightand relative maternal liver weight were unaffected. Relativematernal kidney weight was slightly (7–8%) increased atall dose levels, but there was no evidence of a dose response.Thus, the maternal NOAEL for rats was 300 mg/kg/day, based ondecreased maternal weight gain during treatment at 1000 mg/kg/day. HCTZ had no effect on prenatal mortality, fetal growth,or morphological development in rats. The developmental NOAELwas l000 mg/kg/day. In summary, oral administration of HCTZto mice at doses up to 3000 mg/kg/day and rats at doses up to1000 mg/kg/day during organogenesis produced no evidence ofdevelopmental toxicity in either species, in spite of mild maternaltoxicity in rats at 1000 mg/kg/day.     

Acute toxicity, subchronic dermal toxicity, and delayed contact sensitization evaluations of dicyclopentenyloxyethyl methacrylate in rabbits and guinea pigs

The subchronic dermal toxicity of dicyclopentenyloxethyl methacrylate (DPOMA) was evaluated in young adult New Zealand White rabbits, and its potential to produce delayed contact sensitization was evaluated in Harley guinea pigs by a modified Buehler's closed patch technique. In addition, studies were conducted to evaluate the acute systemic toxicity of DPOMA in rats (oral) and rabbits (dermal), and its eye and skin irritancy in rabbits. In the subchronic dermal toxicity study, 4 groups of rabbits were treated percutaneously with DPOMA at 0 (acetone), 10, 107, and 1067 (undiluted) mg/kg X day in a volume of 1 ml/kg, over a 4-wk period. The application sites were unoccluded. No deaths occurred, and no signs of systemic toxicity were observed. No treatment-related effects were seen on body weights, hematology, clinical chemistry, urinalysis, organ weights, or histopathology (except the treated skin). The only treatment-related effect was slight to moderate skin irritation in the mid- and high-dose groups. The severity of skin irritaton was dependent on the number of applications and the concentration of DPOMA. Maximal skin irritation occurred after 1 wk. No skin irritation was seen in the control and low-dose group. In the DCS study, guinea pigs received 6 induction doses of 0.5 ml 100% DPOMA and were challenged with 0.5 ml of 50% (w/v) DPOMA in acetone 2 wk after the last induction treatment. No erythema or edema was observed in any of the challenged guinea pigs in either the treated and control groups. These acute toxicity studies indicate that DPOMA is practically nontoxic by a single exposure via both oral and dermal routes (the oral LD50 in rat and dermal LD50 in rabbits were greater than 5.0 g/kg body weight), slightly irritating to the skin, and inconsequentially irritating to the eyes. The no-observed-effect level (NOEL) for systemic toxicity of DPOMA applied repeatedly to rabbits skin is at least 1067 mg/kg X d. DPOMA is not a strong or moderate skin sensitizer in guinea pigs.     

The Developmental Toxicity of 2-Ethyihexanol Applied Dermally to Pregnant Fischer 344 Rats

Undiluted 2-ethylhexanol (2-EH) was administered by occludeddermal application for 6 hr per day on Gestation Days 6 through15 to pregnant Fischer 344 rats, in range-finding (R) and main(M) studies. The dermal route is considered to be the most relevantfor human exposure. Treatment levels were (R) 0.0, 0.5, 1.0,2.0, and 3.0 ml/kg/day (equivalent to 0, 420, 840, 1680, and2520 mg/kg/day) and (M) 0.0, 0.3, 1.0, and 3.0 ml/kg/day (equivalentto 0, 252, 840, and 2520 mg/kg/day). Controls (0.0 ml/kg/day,sham controls) received deionized water at 3.0 ml/kg/day. Dermal-positivecontrol groups received undiluted 2-methoxyethanol (2-ME) at(R) 0.5 and 1.5 ml/kg/day and (M) 1.0 ml/kg/day as a referencecompound in a similar regimen. An oral reference compound, valproicacid, was administered by gavage in the range-finding studyon Gestation Days 6 through 15 at 400 mg/kg/day. The range-findingstudy employed an untreated (naive) control group. Numbers ofplug-positive females per group were (R) 8 and (M) 25. Maternalweight gain was reduced for 2-EH at 1680 (R) and 2520 (R andM studies) mg/kg/day. Exfoliation and encrustation were seenat the application site in both studies at 840, 1680, and 2520mg/kg. Maternal liver, kidney, thymus, spleen, adrenal, anduterine weights, and gestational and fetal parameters were unaffectedby treatment with 2-EH. There were no treatment-related increasesin the incidence of individual or pooled external, visceral,and skeletal malformations or variations following the applicationof 2-EH. The NOAELs for the maternal toxicity of 2-EH were 252mg/kg/day based on skin irritation and 840 mg/kg/day based onsystemic toxicity. The developmental toxicity NOAEL was at least2520 mg/kg/day, with no teratogenicity. Administration of 2-MEat 840 mg/kg/day resulted in reduced maternal weight gain andfood consumption, increased postimplantation loss, reduced numbersof live fetuses per litter, and reduced fetal body weights perlitter. The incidence of fetal malformations and variationswas increased. Oral administration of VPA produced maternaltoxicity, developmental toxicity, and teratogenicity. The Fischer344 rat is thus susceptible to known rodent teratogens by boththe dermal and oral routes. It is concluded that 2-EH is notdevelopmentally toxic by the dermal route in the Fischer 344rat at and below treatment levels which produce maternal toxicity.