Methemoglobinemia due to ingestion of N,N-dimethyl-p-toluidine, a component used in the fabrication of artificial fingernails

Nail Polish Remover Induced Methemoglobinemia: An Uncommon Occurrence

Methemoglobinemia, defined as hemoglobin's impaired oxygen-carrying capacity due to oxidation from the ferrous (Fe2+) state to the ferric (Fe3+) state, has many well-documented etiologies. One example of an uncommon cause of acquired methemoglobinemia is the ingestion of nail polish remover, which can contain methemoglobin generators such as nitroethane, N,N-dimethyl-p-toluidine, and isobutyl nitrite. We present a case of methemoglobinemia in an 81-year-old male following accidental ingestion of isobutyl nitrite-containing nail polish remover, commonly used as a recreational inhalant. Furthermore, we review potentially toxic substances found in commercially available nail products. This case was designed to identify and efficiently treat a rather uncommon cause of methemoglobinemia induced in this case by a common household item, nail polish remover.

Safety and Efficacy of Nail Products

Over the past several decades, the commercialization of nail cosmetics has increased. From nail polishes to artificial nails, different methods of nail beautification have become popularized. However, the impact of these products remains largely unknown. Governments have passed legislation in attempts to regulate nail cosmetics, but these regulations may not be adequate and are difficult to enforce. Knowledge of the safety and efficacy of nail products remains limited due to the relative dearth of literature published on the topic. This review serves to summarize and interpret the data available regarding common nail products and their safety and efficacy. Nail products such as nail polish, nail polish removers, and artificial nails have shown to have some adverse effects through case reports and studies. Harmful substances such as toluenesulfonamide-formaldehyde resin and methacrylates have been identified in commercial nail products, leading to several adverse effects, but in particular, allergic contact dermatitis. Exposure to substances such as acetonitrile found in removers may have more toxic and caustic effects, especially if ingested. In addition, for nail technicians there are negative effects linked with occupational exposure. Compounds used in nail products may become aerosolized and lead to asthma, eye and throat irritation, and even neurocognitive changes.

Hepatic transcriptomic alterations for N,N-dimethyl-p-toluidine (DMPT) and p-toluidine after 5-day exposure in rats

N,N-dimethyl-p-toluidine (DMPT), an accelerant for methyl methacrylate monomers in medical devices, was a liver carcinogen in male and female F344/N rats and B6C3F1 mice in a 2-year oral exposure study. p-Toluidine, a structurally related chemical, was a liver carcinogen in mice but not in rats in an 18-month feed exposure study. In this current study, liver transcriptomic data were used to characterize mechanisms in DMPT and p-toluidine liver toxicity and for conducting benchmark dose (BMD) analysis. Male F344/N rats were exposed orally to DMPT or p-toluidine (0, 1, 6, 20, 60 or 120 mg/kg/day) for 5 days. The liver was examined for lesions and transcriptomic alterations. Both chemicals caused mild hepatic toxicity at 60 and 120 mg/kg and dose-related transcriptomic alterations in the liver. There were 511 liver transcripts differentially expressed for DMPT and 354 for p-toluidine at 120 mg/kg/day (false discovery rate threshold of 5 %). The liver transcriptomic alterations were characteristic of an anti-oxidative damage response (activation of the Nrf2 pathway) and hepatic toxicity. The top cellular processes in gene ontology (GO) categories altered in livers exposed to DMPT or p-toluidine were used for BMD calculations. The lower confidence bound benchmark doses for these chemicals were 2 mg/kg/day for DMPT and 7 mg/kg/day for p-toluidine. These studies show the promise of using 5-day target organ transcriptomic data to identify chemical-induced molecular changes that can serve as markers for preliminary toxicity risk assessment.

N,N-dimethyl-p-toluidine, a component in dental materials, causes hematologic toxic and carcinogenic responses in rodent model systems

Because of the potential for exposure to N,N-dimethyl-p-toluidine (DMPT) in medical devices and the lack of toxicity and carcinogenicity information available in the literature, the National Toxicology Program conducted toxicity and carcinogenicity studies of DMPT in male and female F344/N rats and B6C3F1/N mice. In these studies, a treatment-related macrocytic regenerative anemia characterized by increased levels of methemoglobin and Heinz body formation developed within a few weeks of DMPT exposure in rats and mice. DMPT induced nasal cavity, splenic, and liver toxicity in rats and mice at 3 months and 2 years. DMPT carcinogenic effects were seen in the liver of male and female rats and mice, the nasal cavity of male and female rats, and the lung and forestomach of female mice. In rodents, DMPT is distributed to many of the sites where toxic and carcinogenic effects occurred. DMPT-induced oxidative damage at these target sites may be one mechanism for the treatment-related lesions. Methemoglobinemia, as seen in these DMPT studies, is caused by oxidation of the heme moiety, and this end point served as an early alert for other target organ toxicities and carcinogenic responses that followed with longer term exposure.

Acrylamine-induced autoimmune phenomena

The objective of this study is to document a series of cases of occupationally derived autoimmune disease. Individuals with occupational exposure to acrylamides were evaluated clinically and biochemically/immunologically for evidence of autoimmune disease. Symptoms and signs and immuno-reactivity were monitored during exposure-free and re-exposure as part of the individuals' clinical evaluation. Six individuals with occupational acrylamide exposure had clinical and laboratory alterations characteristic of drug-induced autoimmune disease, specifically lupus, anti-phospholipid syndrome, Sjogren's syndrome, scleroderma, and polymyositis. The similarity of the full spectrum of disease in the reported patients to that found with procainamide strongly suggests the effects of occupational exposure. This uncontrolled study suggests the need for a full epidemiologic analysis of all individuals working with such occupational exposure, including full clinical and immunological examination.

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.

Disposition of [14C]N,N-dimethyl-p-toluidine in F344 rats and B6C3F1 mice

N,N-Dimethyl-p-toluidine (DMPT) is used as a polymerization accelerator, in industrial glues, and as an intermediate in dye and pesticide synthesis. There is potential for human exposure to DMPT. The disposition of oral and intravenous (i.v.) doses of [14C]DMPT in F344 rats and B6C3F1 mice was investigated. A single i.v. (2.5 mg/kg) or oral (2.5, 25, or 250 mg/kg) dose of [14C]DMPT (1-25 microCi) was administered in an aqueous vehicle to male rats and mice. The 25-mg/kg oral dose was administered to females to investigate possible gender differences in disposition. However, no striking gender differences were observed. Since toxicity studies conducted elsewhere used a corn oil vehicle, the 250-mg/kg oral dose also was administered in corn oil to male rats; disposition was not dependent on vehicle. Excreta (through 24 h) and tissues collected at sacrifice were analyzed for total radioactivity. Dose-dependent differences in toxicity and disposition were observed. Toxicity at the 250-mg/kg oral dose to male mice was consistent with acute renal failure. At the same dose, male rats exhibited clinical signs of toxicity through 12 h but were clinically normal by 24 h. At lower oral doses, [14C]DMPT-derived radioactivity was well absorbed and rapidly excreted, primarily in urine.

Optimisation of the composition of an acrylic bone cement: application to relative amounts of the initiator and the activator/co-initiator in Surgical Simplex P

In cemented arthroplasties, the two-part self-curing acrylic bone cement is currently the only material used for anchoring the total joint replacement to the contiguous bone. In virtually all commercially available formulations of this cement, the agents used for the initiation and activation/co-initiation of the radical polymerisation reaction are benzoyl peroxide (BPO) and N, N dimethyl-para-toluidine (DMPT), respectively. There are no reports in the open literature on the rationale for the amounts of these and other constituents in the formulations of the cement. Given the concerns that have been raised in the literature regarding the effect of residual DMPT on the body, it is important to keep the starting amounts of BPO and DMPT as high and as low, respectively, as possible. In the present work, the focus is on the relative amounts of these two agents in the case of one widely used commercial formulation, Surgical Simplex(R) P. Thirty variants of this cement were formulated, covering three concentrations of the co-polymer/BPO (75%, 80%, and 85% of the mass of the powder) and DMPT amounts (ranging from 0.8 %v/v to 2.4% v/v.) The setting time (t(set)), the peak temperature reached during the cement polymerisation process (T(max)), and the ultimate compressive strength (UCS) of each of the formulations were determined in accordance with procedures specified in ISO 5833. A critical examination of all the results indicated that the optimum ratio of the concentration of the initiator (BPO embedded in the PMMA-sytrene co-polymer) to that of the activator/co-initiator (DMPT) in Surgical Simplex(R) P is 57.14 (80%w/w co-polymer + BPO per 1.4%v/v DMPT). The mean values of t(set), T(max), and UCS of this optimum formulation were determined to be 12.30 min, 68 degrees C, and 101 MPa, respectively, all of which are within the limits specified in ISO 5833. The commercially available formulation of this cement contains 2.5%v/v DMPT, while the optimum formulation, as found in the present work, has 44% less DMPT, which may translate to a smaller amount of residual DMPT that is available for elution into the periprosthetic tissue in a cemented arthroplasty, over the in vivo life of the joint replacement.

Side effects of nail cosmetics

Cosmetics applied on the nail encompass three types: (1) coatings that harden upon evaporation; (2) coatings that polymerize; and (3) stick-on nail dressings (synthetic covers). The adverse reactions induced by the two first types present with both local reactions and distant contact dermatitis. Whereas nail enamel applications result especially in ectopic contact dermatitis, polymerizing coatings and synthetic covers represent the main culprit for sometimes severe, local reactions. Whatever the nature of the nail cosmetics, they may produce some adverse reactions. They include: (1) local reactions to cosmetics applied on the nail; (2) distant reactions resulting from the use of nail cosmetics; (3) systemic side effects of nail cosmetics; and (4) infection risks from nail cosmetics.

Nail beauty therapy: an attractive enhancement or a potential hazard?

Nail coatings which harden upon evaporation and coatings that polymerize may produce some reactions at the site of application to the nail itself, and distant reactions when small amounts of nail cosmetics are transferred by the hand to other areas of the skin. Nail cosmetic hazards may be occupational, or accidental, especially in children. Individuals wearing artificial nails tend to wear their nails longer, and are more careful about their nails when washing their hands. The sanitary conditions for the application of artificial nails are therefore paramount in preventing nail infections.

Nail art: a review of current infection control issues

Nail art or nail technology is a form of nail decoration which frequently entails applying extensions to the natural nail and then adding decorative effects. There have been a number of outbreaks of infection which have implicated nail art. These infections are likely to be as a result of difficulties in cleaning and maintaining the nail extensions. Nail art appears to be incompatible with clinical care.

Treatment of high-risk, refractory acquired methemoglobinemia with automated red blood cell exchange

Ingestion of strong oxidant substances may result in acquired methemoglobinemia, a clinical condition in which the oxidized blood hemoglobin is incapable of delivering oxygen to the tissues, and the patient becomes cyanotic. Traditional first-line therapy consists of infusion of methylene blue, whose action depends on the availability of reduced nicotinamide adenine nucleotide phosphate (NADPH) within the red blood cell (RBC). Some patients, particularly those who are deficient in glucose-6-phosphate dehydrogenase (G6PD), will not benefit from methylene blue. In these patients, and in some patients who have ingested very strong oxidants, methylene blue may also precipitate Heinz body hemolytic anemia. We present a case of severe, acquired methemoglobinemia in a 26-month-old, 9.8-kg boy with G6PD deficiency. He was cyanotic, in respiratory failure, intubated in a pediatric intensive care unit. In typical fashion, he did not respond to methylene blue. Manual exchange of two whole blood volumes, performed over 4 1/2 hr, also failed to resolve his severe methemoglobinemia. An automated RBC exchange (1.3 RBC volume), lowered his methemoglobin content from 31.8% to 7% in a single 40-min procedure. Thereafter his methemoglobin level continued to decrease rapidly and spontaneously. He was discharged home 2 days later, with 0.4% methemoglobin. To our knowledge, this is the first report to demonstrate the (potentially superior) effectiveness of automated RBC exchange for treatment of patients with high-risk acquired methemoglobinemia, that is, those with G6PD deficiency or who have ingested strong oxidants.

Nail primer cosmetics: correlations between product pH and adequacy of labeling

BACKGROUND

We have previously reported on injuries suffered by young children exposed to methacrylic acid-containing nail primers and the need for public education efforts concerning this potential household hazard. However, some primers contain alternative ingredients, which may or may not pose the same risk; product labeling information is variable and may be confusing to consumers.

OBJECTIVE

To investigate the relationship between pH of different primer products, product contents, and appropriateness of product labeling and packaging.

METHODS

Twenty-three commercially available primers were grouped by product contents: (methacrylic acid vs others). Product pH was measured and product labels were scored on 7 warning points: "poison and/or corrosive," a "caution to avoid contact and/or to use a barrier when handling the product," a "skin first aid," and "eye first aid," an "ingestion first aid," a caution to "keep out of reach of children," and a "in emergency, contact a poison center." A summative "global hazard notification score" was calculated for each product. Data were analyzed using correlations and the two-sample t-test.

RESULTS

None of 23 products tested were contained in a child-resistant container and none included all 7 label items. Product pH ranged from 1.90-8.55 (mean pH 4.59 +/- 1.99); 20 products had pH < 7.0. Only 1 product advised, in the event of a poisoning, that a poison center be contacted. Of 20 acidic products, only 7 alerted users that the contents could cause burns. The mean global hazard notification score (MAX = 7) was 3.6; global hazard notification score did not correlate with pH. Methacrylic acid-containing products had a lower pH (mean 3.43 +/- 0.78) than those without methacrylic acid (mean 5.34 +/- 2.18), p = 0.008. When the primer bottle was separated from the rest of the packaging which comprised the artificial nail "kit," 50% of products lost all of their warning information.

CONCLUSIONS

Most, but not all, artificial nail primers analyzed in this study were highly acidic. Labeling and packaging of many nail primers are inadequate, given the potential of methacrylic acid in these products to cause burns and the toxicity of most nail primers. We agree with the Consumer Product Safety Commission's recently proposed rule to require cosmetic manufacturers to repackage methacrylic acid-containing household products in child-resistant containers. We also urge manufacturers to alert consumers to the hazards of nail primers by better labeling. Manufacturers should also investigate the feasibility of either substituting other chemicals or lowering the concentration of methacrylic acid.

Rebound severe methemoglobinemia from ingestion of a nitroethane artificial-fingernail remover

We describe life-threatening methemoglobinemia in a child who ingested a nitroethane artificial-fingernail remover initially mistaken to be an acetone-based polish remover. Nitroethane-induced methemoglobinemia may be delayed and recurrent; patients ingesting this substance may warrant close observation for at least 24 hours. Care givers are cautioned to determine the precise substance involved in ingestions of potentially toxic fingernail products.

Nitroethane poisoning from an artificial fingernail remover

Confusion between acetone fingernail polish removers and artificial fingernail products containing acetonitrile and N,N-dimethyl-p-toluidine has resulted in pediatric morbidity and mortality. In the present case, a 20-month-old boy drank less than one ounce of Remove Artificial Nail Remover containing 100% nitroethane. In the emergency department he displayed cyanosis and 39% methemoglobinemia. Following intravenous methylene blue, the child's methemoglobin level dropped to 5.7% and he recovered uneventfully. Toxicity from nitroethane has not previously been reported in humans. Poison centers and emergency department personnel should be alert to another nail product which may be easily confused with acetone-containing nail polish removers.