Acute and subacute inhalation toxicity studies of a new broad spectrum insect repellent, N,N-diethylphenylacetamide

N,N-Diethylphenylacetamide (DEPA) is an inexpensive, long-acting and broad spectrum insect repellent. The acute LC50 for a 4-h exposure of DEPA aerosol was found to be 1.451 mg l-1 (1.290-1.633) in male and 1.375 mg l-1 (1.307-1.447) in female rats. DEPA did not cause delayed deaths. Acute exposure to 0.9 LC50 revealed that liver might be a target organ for DEPA toxicity. On subacute exposures to 0.2, 0.6 and 0.8 LC50 for 6 h per day, 5 days a week for 2 weeks, there was no significant change in the 0.2 LC50 group, as evaluated by the body weight gain and organ body weight ratio. The minimal changes observed in the 0.6 LC50 group were of reversible type as the animals recovered on cessation of exposure. A massive concentration of 0.8 LC50 produced lethal effects. The study shows that DEPA has a low mammalian toxicity by inhalation as was found earlier with cutaneous application of the insect repellent.     

Toxicity and metabolism of a new insect repellent N,N-diethylphenylacetamide in mice, rats and guinea pigs on cutaneous application

Cutaneous LD50 of N,N-diethylphenylacetamide (DEPA), a new multi insect repellent was 2200, 3200 and 7100 mg/kg body weight in female mice, rats and guinea pigs; and 1600 and 4000 mg/kg in male mice and rats indicating a high degree of safety on skin contact. Dermal application of DEPA to young growing rats for 21 days at a dose of 50 mg/kg did not exert any adverse effects while massive doses of 500 and 1000 mg/kg caused marked reduction of body weight gain and lowering of activities of serum alanine aminotransferase, aspartate aminotransferase and cholinesterase. Along with DEPA, N-ethylphenylacetamide, phenylacetamide and phenylacetic acid were detected in the urine of DEPA treated mice, rats and guinea pigs.     

N,N-diethylphenylacetamide, an insect repellent: absence of mutagenic response in the in vitro Ames test and in vivo mouse micronucleus test

N,N-diethylphenylacetamide (DEPA), a promising new insect repellent, was tested for mutagenicity in the in vitro Ames Salmonella/microsome mutagenicity test and the in vivo mouse micronucleus test. For the Ames test, DEPA was assayed both in the presence and absence of Aroclor 1254-induced rat-liver S-9 mix (5 and 20% S-9 fraction), using five tester strains of Salmonella typhimurium--TA97a, TA98, TA100, TA102 and TA104. For the micronucleus test, mice were exposed to DEPA through ip injection for 2 and 5 days in separate experiments, and bone marrow and peripheral blood were sampled 6 and 48 hr after the final injection, respectively. DEPA did not induce a mutagenic response in the Ames test, and mouse bone marrow and peripheral blood micronucleus tests. DEPA was not considered cytotoxic, as a depression of the percentage PCE was not observed at any dose in the range of 1 to 100 mg/kg body weight with either treatment protocol of the micronucleus test.     

Review of the biodistribution and toxicity of the insect repellent N,N-diethyl-m-toluamide (DEET)

A review of the biodistribution and toxicity of the insect repellent N,N-diethyl-m-toluamide (DEET) is presented. Workers using repellent containing this compound may be exposed to greater than 442 g in 6 mo. In human studies, variable penetration into the skin of from 9 to 56% of a topically applied dose and absorption into the circulatory system of approximately 17% have been reported. Excretion of DEET by humans was initially rapid but not as complete as in animal models. Only about one-half of the absorbed DEET was excreted by humans over 5 d. Depot storage of DEET in the skin was also documented. Skin irritant effects, including scarring bullous dermatitis in humans, were reported. One animal study that reported embryotoxicity could not be confirmed by other investigators. The limited testing for mutagenicity and carcinogenicity provided negative results. Neurotoxic effects were observed in workers exposed to 4 g or more per week. Six young girls developed encephalopathies after exposure to unspecified amounts of DEET ranging from small to massive doses. Three of these girls later died. The cause of their death has not been resolved. Because of the lack of information, further research into the absorption, carcinogenicity, and neurotoxic effects is needed.     

Distribution and metabolism of insect repellant N,N-diethylphenylacetamide on oral exposure in rats

Oral toxicity, distribution and metabolism of a new multi-insect repellant, N,N-diethylphenylacetamide (DEPA) was studied in rats. On administration of DEPA (851 mg/kg body wt.) labelled with 14C blood, liver, stomach and stomach contents had 2.65, 3.97, 12.07 and greater than 50.66% radioactivity, respectively, after 20 min. Gas chromatographic analysis showed presence of both DEPA and its metabolite N-ethylphenylacetamide (EPA) in blood, liver, kidneys and lungs while only DEPA was present in stomach and stomach contents. EPA, phenylacetamide and conjugated phenylacetic acid were excreted along with unmetabolized parent compound in urine of rats when a low oral dose of DEPA (70 mg/kg body wt.) was administered. Activities of erythrocyte cholinesterase and carbonic anhydrase did not change significantly upon acute oral exposure to DEPA.     

Some cardiovascular effects of the insect repellent N,N-diethyl-m-toluamide (DEET)

Initial toxicological safety evaluations of the insect repellent N,N-diethyl-m-toluamide (DEET) indicated a potential hypotensive effect. The current study was initiated in order to pursue this aspect of DEET toxicity and to elucidate potential mechanisms for this response. Sublethal intraperitoneal injections of DEET in anesthetized rats were found to decrease mean blood pressure and heart rate in a dose-related fashion. Doses ranged from 56 to 225 mg/kg. Dogs treated with 225 mg/kg of DEET exhibited a similar hypotension and bradycardia. Cardiac output was also significantly reduced but stroke volume and total peripheral resistance were not altered. Lead II ECG changes included small increases in P-R and Q-T intervals. In a series of pharmacological studies in rats, DEET was found to decrease the hypotension and bradycardia associated with acetylcholine injection; epinephrine, norepinephrine, and histamine responses were not altered. Atropine pretreatment reduced but did not eliminate the hypotensive effects of DEET.     

In-vitro permeation of the insect repellent N,N-diethyl-m-toluamide (DEET) and the sunscreen oxybenzone

The permeation behaviours of the insect repellent N,N-diethyl-m-toluamide (DEET) and the sunscreen oxybenzone were assessed in a series of in-vitro diffusion studies, using piglet skin and poly (dimethylsiloxane) (PDMS) membrane. The transmembrane permeability of DEET and oxybenzone across piglet skin and PDMS membrane was dependent on dissolving vehicles and test concentrations. An enhanced permeation increase across piglet skin was found for DEET and oxybenzone when both compounds were present in the same medium (DEET: 289% in propylene glycol, 243% in ethanol and 112% in poly(ethylene glycol) (PEG-400); oxybenzone: 139% in PEG-400, 120% in propylene glycol and 112% in ethanol). Permeation enhancement was also observed in PDMS membrane (DEET: 207% in ethanol, 124% in PEG-400 and 107% in propylene glycol; oxybenzone: 254% in PEG-400, 154% in ethanol and 105% in propylene glycol). PDMS membrane was found to be a suitable candidate for in-vitro diffusion evaluations. This study shows that the permeations of the insect repellent DEET and the sunscreen oxybenzone were synergistically enhanced when they were applied simultaneously.     

伤必止的皮肤毒性实验研究

目的研究伤必止对动物皮肤的毒性作用。方法对健康家兔进行皮肤急性毒性实验、皮肤刺激性实验,对健康豚鼠进行皮肤过敏实验。结果伤必止对家兔完整及破损皮肤均未引起急性毒性反应和刺激反应,对豚鼠无致敏作用。结论伤必止应用于临床安全、无毒。     

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.     

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 conduct of a two-generation reproductive toxicity study via dermal exposure in the Sprague-Dawley rat--a case study with KBR 3023 (a prospective insect repellent).

KBR 3023, 1-(1-methyl-propoxycarbonyl)-2-(2-hydroxyethyl)-piperidine, a prospective insect repellent being developed by the Bayer Corporation, was evaluated for reproductive toxicity in the Sprague-Dawley rat. As the intended human use of the test compound is topical, the test system was also exposed to the compound via the dermal route. Specifically, the adult rats (P generation) were fitted with Elizabethan collars, to reduce the likelihood of oral ingestion, and dermally administered either 0, 50, 100, or 200 mg KBR 3023/kg body weight throughout the study (5 d/week) beginning at the onset of the 10-week premating period and continuing through the mating, gestation, and lactation phases. Clinical signs and changes in body weight and food consumption were assessed throughout the study. All adults and neonates underwent a gross necropsy examination. Tissues retained for microscopic examination from all adult animals included the kidney, liver, pituitary, reproductive organs, and samples of skin from the shaved dose site. In addition to the parameters noted above, the animals were evaluated for the effect of the test compound on estrous cycling, mating, fertility, gestation length, litter size, pup sex ratio, and pup viability. There were no test compound-related clinical signs or effects on body weight or food consumption observed in either the adults or the pups during any phase of the study. There were no compound-related effects on any reproductive or litter parameters. Dermal findings at the dose site (acanthosis and hyperkeratosis) were noted in both generations. Other than the dermal findings, no compound-related necropsy findings were seen in either the adults or the pups. No compound-related histopathologic findings were noted in the reproductive tissues of either the males or females. Based on these results, KBR 3023, administered as described in this study at dose levels as high as 200 mg/kg body weight (the physical limit of dermal application for this compound), did not demonstrate any reproductive toxicity.     

Subchronic dermal toxicity studies of Alcide Allay gel and liquid in rabbits

Alcide is a germicidal agent which is highly effective in killing a wide range of bacteria and fungi. 2.0 g kg-1 Allay gel or placebo were applied once per day while 3.0 g kg-1 Allay liquid or placebo were administered three times per day over a 30 day period to the skin of albino rabbits. Allay gel and liquid contained either of two concentrations of sodium chlorite and lactic acid as active ingredients. The concentration of active ingredients, sodium chlorite and lactic acid, in the low dose gel was 25% of high dose gel and low dose liquid was 60% of high dose liquid. Moderate to severe erythema was observed only in the high dose gel group after 7 days of treatment, but skin appeared visibly normal by day 18. Histologically fixed skin at day 30, however, showed inflammatory changes in the high and low dose gel groups and hyperkeratosis in all gel groups. At the termination of the study, mean corpuscular hemoglobin concentration decreased significantly in the Allay gel and liquid groups compared to an untreated control group. In all gel treatments, BUN/creatinine levels decreased significantly. Hematology and clinical chemistry parameters, however, were within the normal range of values for the gel and liquid groups, indicating no clinically significant changes due to Allay treatment. Pancreas/body weight ratios were significantly reduced in all gel groups, while spleen, pancreas and ovary/body weight ratios were significantly higher in both liquid dosage groups. No histological changes were observed in any of these organs.     

Identification and determination of urinary metabolites of 2-isopropylnaphthalene in rabbits

Four unconjugated metabolites, which were produced through the oxidation of the isopropyl chain of 2-isopropylnaphthalene (2-IPN), were isolated from the urine of rabbits receiving 2-IPN orally and identified: 2-(2-naphthyl)propionic acid, 2-(2-naphthyl)-2-propanol, 2-(2-naphthyl)-1,2-propanediol, and 2-(2-naphthyl)-2-hydroxypropionic acid, together with a small amount of the unchanged compound. Further, the unconjugated metabolites, which were produced through the oxidation of the naphthalene ring, were isolated and identified: 2-isopropylnaphthols and 2-isopropyl-5,6 (or 7,8)-dihydronaphthalene-5,6 (or 7,8)-diol. The identification of these metabolites was made by means of TLC, GLC, MS, IR, GC/MS, and FT-NMR. The presence of glucuronides of metabolites B, C, D, F, and H was also suggested by TLC and GLC of the extract obtained after hydrolysis by beta-glucuronidase. In addition, quantitative determination of the metabolites indicated that the total urinary excretion of the metabolites except 2-isopropylnaphthols in 24 hr after administration was about 29% of the dose.     

The metabolism of mianserin in women, rabbits, and rats: identification of the major urinary metabolites

The biotransformation of orally administered 3H-mianserin was investigated in female human subjects, rabbits, and rats by identification of the major urinary metabolites. Three days after dosing, the urinary excretion of radioactivity was 53% in women, 36% in rats, and 80% in rabbits. In the women's urine, 15% of the administered dose was excreted in the form of mianserin (conjugated plus nonconjugated); in the animal species this quantity was 1-2%. Mianserin was predominantly metabolized to 8-hydroxy analogs in all species; in rats, 8-hydroxydesmethylmianserin was the principal metabolite. Demethylation was an important metabolic pathway in the animal species, but not in women. Novel N-formyl compounds were detected in the urine of both animal species, but the possibility that these were artifacts formed during extraction with chloroform cannot be ruled out. Trace amounts of two compounds in which the piperazine moiety of mianserin was absent, 11H-dibenz[b,e]azepine and 11 H-dibenz[b,e]azepine-2-ol, were identified in the urine of rabbits and rats, respectively.     

Distribution and excretion of a new insect repellent, 14C-DEM, in the mouse after intravenous, cutaneous, and oral administration

The distribution of 14C after administration of 14C-DEM was qualitatively similar irrespective of the administration route (intravenous, cutaneous or oral). The major accumulation sites were lacrimal and nasal glands, parotis, liver, and kidney. The main excretion was through the urine and only minor quantities through the faeces and the expired gases. It could be confirmed that the new repellent had a low skin uptake.     

Some new urinary metabolites of famprofazone and morazone in man

The human urinary metabolism of two pyrazolone derivatives, morazone and famprofazone, has been investigated. After administration of morazone, the metabolites p-hydroxymorazone and phenazone-4-carboxylic acid were excreted in addition to the known metabolite, phenmetrazine, and unchanged morazone. Metabolism of famprofazone led to the formation of methamphetamine; the pyrazolone moiety was excreted as 3-hydroxymethyl-propyphenazone.     

Dermal absorption of the insect repellent DEET (N,N-diethyl-m-toluamide) in rats and monkeys: effect of anatomical site and multiple exposure

The dermal absorption of 14C-ring-labeled DEET (N,N-diethyl-m-toluamide) applied in acetone to the skin of Sprague-Dawley rats and rhesus monkeys for 24 h was determined. Absorption in rats dosed middorsally was 36 +/- 8% with a urinary excretion half-life (t1/2) of 20 h. Both the extent and rate of absorption in monkeys were highly dependent on anatomic site, with 14 +/- 5% (t1/2 = 4 h) penetrating the forearm, 33 +/- 11% (t1/2 = 6 h) the forehead, 27 +/- 3% (t1/2 = 7 h) the dorsal forepaw, and 68 +/- 9% (t1/2 = 8 h) the ventral forepaw. Since DEET is commonly applied frequently by the same individual, the effect of multiple exposure was investigated. No significant difference (p greater than or equal to .3) was obtained either between the total percentage absorbed dermally with single (36 +/- 8%; t1/2 = 20 h) as compared with three (31 +/- 5%; t1/2 = 16 h) DEET applications at 2-h intervals to rats, or between single (14 +/- 5%; t1/2 = 4 h) as compared with three (12 +/- 1%; t1/2 = 4 h) applications at 0.5-h intervals to monkey forearm. A DEET metabolite detected in urine 4 h following topical exposure in humans was extractable following either acid (HCl) hydrolysis or urine treatment with beta-glucuronidase and was identified as ethyltoluamide (parent ion 163; base ion 119) following HPLC purification and characterization by GC/MS.     

N,N'-diethyl-m-toluamide (m-DET): analysis of an insect repellent in human urine and serum by high-performance liquid chromatography.

A procedure for monitoring m-DET in human urine and serum is described. m-DET is removed from the urine specimen by partitioning into diethyl ether, but solid-phase extraction is used to remove it from human serum. The urine and serum m-DET values are determined by HPLC with a UV detector. The limit of detection was 0.09 micrograms/mL in urine and 0.09 micrograms/g for serum. The percent of m-DET recovered from human urine spiked between 0.50 and 8.00 micrograms/mL was 90 +/- 5.4%. For human serum spiked between 0.25 and 10.00, the percent recovered was 96 +/- 5.9%. The pooled relative standard deviations (RSD) for spiked matrices were 0.06 for urine and 0.06 for serum.     

Identification of urinary metabolites of orally administered N,N-dimethyl-p-toluidine in male F344 rats

The metabolism of orally administered N,N-dimethyl-p-toluidine (DMPT) in male F344 rats was investigated. The rat urinary metabolite profile was determined by analytical reverse-phase high performance liquid chromatography (HPLC). Four radiolabeled peaks were observed, isolated, and purified by solid-phase extraction (SPE) and preparative HPLC methods. The 4 peaks were identified as p-(N-acetylhydroxyamino)hippuric acid (M1), DMPT N-oxide (M2), N-methyl-p-toluidine (M3), and parent DMPT. Metabolites M1 and M2 were identified by spectrometric and spectroscopic methods, including mass fragmentation pattern identification from both liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry, and from chemical analysis of nuclear magnetic resonance spectra. Structural confirmation of metabolite M2 was accomplished by comparison with a synthetic standard. Peaks M3 and the peak suspected to be DMPT were identified by comparison of their HPLC retention times and mass fragmentation patterns with authentic standards of N-methyl-p-toluidine and DMPT, respectively. DMPT metabolism is similar to that reported for N,N-dimethylaniline.