NOTES ON A CASE OF POISONING BY HYDROQUINONE

Developmental Neurotoxic Effects of Percutaneous Drug Delivery: Behavior and Neurochemical Studies in C57BL/6 Mice

Dermatosis often as a chronic disease requires effective long-term treatment; a comprehensive evaluation of mental health of dermatology drug does not receive enough attention. An interaction between dermatology and psychiatry has been increasingly described. Substantial evidence has accumulated that psychological stress can be associated with pigmentation, endocrine and immune systems in skin to create the optimal responses against pathogens and other physicochemical stressors to maintain or restore internal homeostasis. Additionally, given the common ectodermal origin shared by the brain and skin, we are interested in assessing how disruption of skin systems (pigmentary, endocrine and immune systems) may play a key role in brain functions. Thus, we selected three drugs (hydroquinone, isotretinoin, tacrolimus) with percutaneous excessive delivery to respectively intervene in these systems and then evaluate the potential neurotoxic effects. Firstly, C57BL/6 mice were administrated a dermal dose of hydroquinone cream, isotretinoin gel or tacrolimus ointment (2%, 0.05%, 0.1%, respectively, 5 times of the clinical dose). Behavioral testing was performed and levels of proteins were measured in the hippocampus. It was found that mice treated with isotretinoin or tacrolimus, presented a lower activity in open-field test and obvious depressive-like behavior in tail suspension test. Besides, they damaged cytoarchitecture, reduced the level of 5-HT-5-HT1A/1B system and increased the expression of apoptosis-related proteins in the hippocampus. To enable sensitive monitoring the dose-response characteristics of the consecutive neurobehavioral disorders, mice received gradient concentrations of hydroquinone (2%, 4%, 6%). Subsequently, hydroquinone induced behavioral disorders and hippocampal dysfunction in a dose-dependent response. When doses were high as 6% which was 3 times higher than 2% dose, then 100% of mice exhibited depressive-like behavior. Certainly, 6% hydroquinone exposure elicited the most serious impairment of hippocampal structure and survival. The fact that higher doses of hydroquinone are associated with a greater risk of depression is further indication that hydroquinone is responsible for the development of depression. These above data demonstrated that chronic administration of different dermatology drugs contributed into common mental distress. This surprising discovery of chemical stressors stimulating the hippocampal dysfunction, paves the way for exciting areas of study on the cross-talk between the skin and the brain, as well as is suggesting how to develop effective and safe usage of dermatological drugs in daily practice.

Status epilepticus in a child secondary to ingestion of skin-lightening cream

The popularity of the Internet and online media has led to the increased availability of prescription-strength, skin-lightening products contributing to a rise in their use among people with various skin pigment disorders. These products may contain a wide variety of active ingredients such as heavy metals, hydroquinone, and corticosteroids that can be highly toxic, especially after prolonged application. For decades, there have been case reports of both corticosteroid and heavy metal toxicity related to skin-lightening cream use. We report a case of a child who developed status epilepticus after ingesting a skin-lightening solution containing 2% hydroquinone. The toxicodynamics of hydroquinone and its effects on the central nervous system are discussed.

Hydroquinone: Acute and subchronic toxicity studies with emphasis on neurobehavioral and nephrotoxic effects

Hydroquinone (HQ) is a common water-soluble constituent of foods, an ingredient in skin lightening preparations, a photographic developer, and an antioxidant used in the preparation of industrial polymers. In this series of studies, aqueous solutions of HQ were given by gavage to male and female Sprague-Dawley rats to determine the acutely lethal dose, the clinical signs of behavioral toxicity associated with doses at or near a dose causing mortality, and the effects of the administration of dose levels resulting in acutely observable behavioral effects when administered 5 days/week for 13 weeks. The acute dermal toxicity of HQ in rabbits was also determined. For the acute oral toxicity study, groups of five male and five female rats were administered single oral doses of 375, 345, 315, or 285 mg/kg. At all dose levels, animals exhibited minor to moderate tremors and minor convulsions within the first hour after dosing. The acute oral LD50 value for both sexes combined was >375 mg/kg. Dermal application of 2000 mg/kg HQ to rabbits under an occlusive wrap for 24 h did not result in neurobehavioral effects or mortality. Subchronic exposure was accomplished by administration of doses of 200, 64, 20, or 0 mg/kg/day of HQ in water to groups of male and female rats study (10/sex/group). A functional observational battery (FOB) was used to detect neurobehavioral effects prior to HQ exposure and postexposure at 1, 6, and 24 h and 7, 14, 30, 60, and 91 days. Daily clinical observations were also recorded for each animal. Doses of 200 or 64 mg/kg HQ resulted in acutely observable behavioral effects including tremors and reduced activity. Tremors occurred within one hour of dosing and resolved by the 6-h examination. Brain weights were not altered by HQ administration, but mean terminal body weight was reduced approximately 7% for the 200 mg/kg males. Neuropathologic examination of the CNS and PNS, including special stains for myelin and axonal process, did not reveal any morphologic lesions associated with HQ administration or secondary to repetitive CNS stimulation by HQ. The nephrotoxic effects observed in Fischer 344 rats after HQ exposure was not observed in this study with Sprague-Dawley rats. Oral doses of >or=64/mg/kg HQ resulted in acute neurobehavioral effects indicative of CNS stimulation; however, subchronic exposure to dose levels that produced repetitive CNS stimulation by HQ did not result in an exacerbation of acute stimulatory effects over time or morphologic changes in the CNS or PNS or nephrotoxicity.

The toxicology of hydroquinone--relevance to occupational and environmental exposure

Hydroquinone (HQ) is a high-volume commodity chemical used as a reducing agent, antioxidant, polymerization inhibitor, and chemical intermediate. It is also used in over-the-counter (OTC) drugs as an ingredient in skin lighteners and is a natural ingredient in many plant-derived products, including vegetables, fruits, grains, coffee, tea, beer, and wine. While there are few reports of adverse health effects associated with the production and use of HQ, a great deal of research has been conducted with HQ because it is a metabolite of benzene. Physicochemical differences between HQ and benzene play a significant role in altering the pharmacokinetics of directly administered when compared with benzene-derived HQ. HQ is only weakly positive in in vivo chromosomal assays when expected human exposure routes are used. Chromosomal effects are increased significantly when parenteral or in vitro assays are used. In cancer bioassays, HQ has reproducibly produced renal adenomas in male F344 rats. The mechanism of tumorigenesis is unclear but probably involves a species-, strain-, and sex-specific interaction between renal tubule toxicity and an interaction with the chronic progressive nephropathy that is characteristic of aged male rats. Mouse liver tumors (adenomas) and mononuclear cell leukemia (female F344 rat) have also been reported following HQ exposure, but their significance is uncertain. Various tumor initiation/promotion assays with HQ have shown generally negative results. Epidemiological studies with HQ have demonstrated lower death rates and reduced cancer rates in production workers when compared with both general and employed referent populations. Parenteral administration of HQ is associated with changes in several hematopoietic and immunologic endpoints. This toxicity is more severe when combined with parenteral administration of phenol. It is likely that oxidation of HQ within the bone marrow compartment to the semiquinone or p-benzoquinone (BQ), followed by covalent macromolecular binding, is critical to these effects. Bone marrow and hematologic effects are generally not characteristic of HQ exposures in animal studies employing routes of exposure other than parenteral. Myelotoxicity is also not associated with human exposure to HQ. These differences are likely due to significant route-dependent toxicokinetic factors. Fetotoxicity (growth retardation) accompanies repeated administration of HQ at maternally toxic dose levels in animal studies. HQ exposure has not been associated with other reproductive and developmental effects using current USEPA test guidelines. The skin pigment lightening properties of HQ appear to be due to inhibition of melanocyte tyrosinase. Adverse effects associated with OTC use of HQ in FDA-regulated products have been limited to a small number of cases of exogenous ochronosis, although higher incidences of this syndrome have been reported with inappropriate use of unregulated OTC products containing higher HQ concentrations. The most serious human health effect related to HQ is pigmentation of the eye and, in a small number of cases, permanent corneal damage. This effect has been observed in HQ production workers, but the relative contributions of HQ and BQ to this process have not been delineated. Corneal pigmentation and damage has not been reported at current exposure levels of <2 mg/m3. Current work with HQ is being focused on tissue-specific HQ-glutathione metabolites. These metabolites appear to play a critical role in the renal effects observed in F344 rats following HQ exposure and may also be responsible for bone marrow toxicity seen after parenteral exposure to HQ or benzene-derived HQ.