Antihistamines and birth defects: a systematic review of the literature

[Ophthalmic agents during pregnancy]

The use of ophthalmic agents during pregnancy and breastfeeding always represents an off-label use. Therefore, the use of drugs must be particularly carefully assessed with respect to the risk-benefit assessment. In this overview the literature databank of the PubMed library, pharmaceutical lists (Red List, Swiss pharmaceutical compendium), guidelines of the specialist societies the German Society of Ophthalmology (DOG), the Swiss Society of Ophthalmology (SOG), the European Glaucoma Society (EGS), the American Academy of Ophthalmology (AAO) and internet portals (embryotox, reprotox) were inspected and recommendations for the use of ophthalmic agents during pregnancy and breastfeeding were derived. More attention should be dedicated to this topic in the specialist societies.

Mastocytosis in Pregnancy

Mastocytosis is a rare neoplastic disorder of the mast cell lineage resulting in unregulated proliferation and activation of mast cells. Symptoms worsen in about one-third of pregnant patients. Treatment focuses on management of symptoms with antimediator therapy (H1 & H2 antihistamines, glucocorticoids, and epinephrine, if required). Medication selection requires care during labor and delivery. Although it is generally considered safe to use a medication patient tolerated before, some common medications may need to be avoided or used with caution (eg, codeine, morphine, nonsteroidal antiinflammatory drugs, vancomycin) if the patient does not have any history of exposure to them.

Analysis of umbilical cord tissue as an indicator of in utero exposure to toxic adulterating substances

In utero drug exposure is a significant public health threat to the well-being and normal development of the neonate. Recently, testing of umbilical cord tissue (UCT) has been employed to measure illicit drug exposure, as drugs used by the mother during the third trimester may be retained in the UCT. Focus has also been given to potential adverse health effects among drug users, resulting from exposure to pharmacologically active adulterants and cutting agents in the street drug supply. The in utero effects of these substances have not been well studied in humans, nor has their presence been demonstrated as a means for assessing adverse health effects in the neonate. Here, we describe the application of a novel test method to analyze UCT for the presence of more than 20 common adulterating/cutting substances via LC/Q-TOF. In total, 300 de-identified UCT samples were analyzed-all had previously tested positive for cocaine or opiates. Generally, the positivity rates of individual compounds were similar between the Cocaine and Opiates Subgroups, apart from levamisole, xylazine, dipyrone (metabolites), and promethazine. Many of the adulterants used in the street drug supply do have legitimate medicinal/therapeutic uses, including several of the compounds most frequently detected in this study. Caffeine and lidocaine were the most frequently identified compounds both individually (>70% each) and in combination with each other. Alternatively, levamisole, an adulterant with no legitimate therapeutic use, was present in 12% of cases. Importantly, this data demonstrates that the detection of traditional drugs of abuse may serve as indicators of potential in utero exposure to toxic adulterating substances during gestation. While there is cause for concern with respect to any unintentional drug exposure, illicit drug use during pregnancy, including uncontrolled dosing, poly-adulterant consumption, and the interactions of these drug mixtures, produces a significant public health threat to the neonate which warrants further study.

Preventive Approaches in Women's Neurology: Prepartum, Pregnancy, and Postpartum

Women's neurology is the subspecialty within neurology concerned with the distinct healthcare needs of women. In this article, we review current literature and expert management strategies regarding disease-specific neurologic concerns of women, with an emphasis on issues related to contraception, pregnancy, and lactation. Health conditions that we discuss in this article include epilepsy, headache, stroke, multiple sclerosis, and Chiari I malformation. Current findings on neurologic disease in women suggest that many women with neurologic disease can safely manage their disease during pregnancy and have healthy children, though pregnancy planning is important in many conditions to mitigate risks and effective contraceptive management is important when pregnancy prevention is desired.

A simple and sensitive LC-MS/MS method for determination of doxylamine in human plasma and its application in a bioequivalence study in healthy Chinese volunteers

A simple, rapid, sensitive and specific LC-MS/MS method was developed and validated for the quantitative determination of doxylamine in human plasma, using isotope doxylamine-d5 as internal standard (IS). The detection was conducted on a QTRAP 5500 tandem mass spectrometer coupled with electrospray ionization (ESI) source in positive ion mode. Quantification was achieved by positive electrospray ionization containing multiple reaction monitoring (MRM) transitions of m/z 271.0→182.0 for doxylamine and m/z 276.2→187.3 for IS. The mobile phase A was methanol, and mobile phase B was 20 mM ammonium acetate (0.2 % formic acid) in water, using a gradient elution procedure at a flow rate of 0.6 mL/min. The method was validated with a sensitivity of 0.500 ng/mL and a linear concentration range of 0.500-200 ng/mL. The inter-batch precision (%CV) was less than 5.4 %, and the accuracy deviation (%RE) ranged from - 10.6 % to 3.7 %; the inter-batch precision (%CV) was less than 6.6 %, and the accuracy deviation (%RE) was ranged from - 2.7 % to 0.1 %. The selectivity, sensitivity, extraction recovery, matrix effect, carryover, dilution reliability, stability and other characteristics were within the acceptable range. This validated method was successfully applied to a bioequivalence study that orally administered 25 mg of doxylamine succinate tablets in 60 healthy Chinese volunteers.

Management of allergic diseases in pregnancy

Allergic diseases like asthma, allergic rhinitis, food allergy, hymenoptera allergy, or atopic dermatitis are highly prevalent in women of childbearing age and may affect up to 30% of this age group. This review focuses on the management of allergic diseases during pregnancy. Furthermore, we discuss the challenges of counseling women with allergic diseases in the reproductive age, including considerations relevant to the ongoing SARS-CoV-2 pandemic. To create the optimal milieu for the unborn child, a multitude of immunological changes occur during pregnancy which may favor type 2 responses and aggravate disease phenotypes. In co-occurrence with suboptimal preconception disease control, this elevated Th2 responses may aggravate allergic disease manifestations during pregnancy and pose a risk for mother and child. Due to limitations in conducting clinical trials in pregnant women, safety data on anti-allergic drugs during pregnancy are limited. The lack of information and concerns among pregnant patients demands counseling on the benefits of anti-allergic drugs and the potential and known risks. This includes information on the risk for mother and child of disease aggravation in the absence of treatment. By doing so, informed decisions and shared decision-making can take place.

Long-Term Functional and Cytoarchitectonic Effects of the Systemic Administration of the Histamine H1 Receptor Antagonist/Inverse Agonist Chlorpheniramine During Gestation in the Rat Offspring Primary Motor Cortex

The transient histaminergic system is among the first neurotransmitter systems to appear during brain development in the rat mesencephalon/rhombencephalon. Histamine increases FOXP2-positive deep-layer neuron differentiation of cortical neural stem cells through H₁ receptor activation in vitro. The in utero or systemic administration of chlorpheniramine (H₁ receptor antagonist/inverse agonist) during deep-layer cortical neurogenesis decreases FOXP2 neurons in the developing cortex, and H₁R- or histidine decarboxylase-knockout mice show impairment in learning and memory, wakefulness and nociception, functions modulated by the cerebral cortex. Due to the role of H₁R in cortical neural stem cell neurogenesis, the purpose of this study was to evaluate the postnatal impact of the systemic administration of chlorpheniramine during deep-layer cortical neuron differentiation (E12–14) in the primary motor cortex (M1) of neonates (P0) and 21-day-old pups (P21). Chlorpheniramine or vehicle were systemically administered (5 mg/kg, i.p.) to pregnant Wistar rats at gestational days 12–14, and the expression and distribution of deep- (FOXP2 and TBR1) and superficial-layer (SATB2) neuronal cortical markers were analyzed in neonates from both groups. The qRT-PCR analysis revealed a reduction in the expression of Satb2 and FoxP2. However, Western blot and immunofluorescence showed increased protein levels in the chlorpheniramine-treated group. In P21 pups, the three markers showed impaired distribution and increased immunofluorescence in the experimental group. The Sholl analysis evidenced altered dendritic arborization of deep-layer neurons, with lower excitability in response to histamine, as evaluated by whole-cell patch-clamp recording, as well as diminished depolarization-evoked [³H]-glutamate release from striatal slices. Overall, these results suggest long-lasting effects of blocking H₁Rs during early neurogenesis that may impact the pathways involved in voluntary motor activity and cognition.

A review of pruritus in pregnancy

Pruritus is a common dermatologic complaint during pregnancy. Pruritus is reported by 23-38% of women during pregnancy, and 2% report severe pruritus. In addition to interfering with sleep and reducing overall quality of life during pregnancy, pruritus may be the first, or only, symptom of an underlying disorder that may impact maternal and fetal outcomes. It is therefore critical for all providers caring for pregnant women to be familiar with pregnancy-specific and non-specific conditions associated with pruritus to most effectively manage this unique population. In this review, we discuss clinical classification of pruritus, a practical approach to the differential diagnosis of pruritus in pregnancy, and focus on updates in the clinical features, diagnosis, management, and prognosis of pregnancy-specific causes of pruritus.

Drastic Decontamination in a Patient With Anaphylaxis

BACKGROUND

Allergic reactions are common symptoms in the emergency department (ED), with anaphylaxis comprising 1-3% of ED visits. Anaphylaxis is a clinical diagnosis. Treatment of anaphylaxis starts with airway, oxygenation, and decontamination, followed by medication administration.

CASE REPORT

We describe a patient who presented to the ED with anaphylaxis complicated by a persistent exposure to the allergen with need for emergent decontamination. Why Should an Emergency Physician be Aware of This? Knowing the treatment of anaphylaxis is critical to prevent morbidity and mortality. This case is a reminder to always remove the offending agent and nuances involved with treating critically ill pregnant patients.

Emedastine During Pregnancy and Lactation: Emedastine Levels in Maternal Serum, Cord Blood, Breast Milk, and Neonatal Serum

Background: Emedastine difumarate is a second-generation antihistamine that is more effective for nasal congestion than first-generation antihistamines. The oral form of emedastine is used for the treatment of allergic rhinitis (AR). However, data characterizing emedastine transfer across the placenta and excretion into breast milk are limited. In this case report, we assessed emedastine concentrations in maternal and neonatal blood, cord blood, and breast milk. Materials and Methods: After the patient provided informed consent, emedastine concentrations in maternal serum, breast milk, cord blood, and neonatal serum were measured while the mother was taking oral emedastine 2 mg once daily. Case Report: A 39-year-old woman with AR received emedastine during pregnancy and lactation. Her female infant was born at 37 weeks of gestation with a birth weight of 2,820 g. Emedastine concentrations in maternal serum at 11.5 and 19.0 hours after maternal dosing were 0.39 and 0.22 ng/mL, respectively. The emedastine concentration in cord blood (19.6 hours after maternal dosing) was 0.18 ng/mL. At 24 hours after delivery (44 hours after maternal dosing), emedastine was under the lower limit of quantification (<0.05 ng/mL) in the infant's serum. Emedastine concentrations in breast milk ranged from 0.06 to 0.44 ng/mL. Calculated infant doses through breast milk were much lower than the clinical dose of emedastine. The infant had normal developmental progress and no detectable drug-related adverse effects. Conclusions: Rates of emedastine transfer into placenta and breast milk were low. Further study is required to assess the safety of emedastine in fetuses and breastfed infants.

Use of antihistamine medications during early pregnancy and selected birth defects: The National Birth Defects Prevention Study, 1997-2011

BACKGROUND

It is estimated that approximately 10-15% of pregnant women report antihistamine use during pregnancy. Although antihistamines are generally considered safe during pregnancy, results from published studies are inconsistent.

METHODS

Using a case-control study design we analyzed 41,148 pregnancies (30,091 cases and 11,057 controls) from the National Birth Defects Prevention Study (1997-2011). Logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals for 64 birth defect groupings in relation to early pregnancy exposure to 14 distinct antihistamines. Models were adjusted for maternal age, race, parity, education level, prenatal care, folic acid use, smoking and alcohol use, and study site.

RESULTS

Approximately 13% of cases and controls were exposed to an antihistamine during early pregnancy. Analyses were restricted to those defects where more than five cases were exposed to the antihistamine of interest, generating 340 analyses which yielded 20 (5.9%) significant positive associations (adjusted ORs ranging from 1.21 to 4.34).

CONCLUSIONS

Only a few of our findings were consistent with previous studies. There is a lack of strong evidence to conclude that birth defects are associated with exposure to antihistamines during early pregnancy.

The Influence of Pregnancy on the Clinical Evolution and Prognosis of Pre-Existing Inflammatory and Autoimmune Skin Disorders and Their Management

BACKGROUND

Although the possible occurrence of typical dermatoses during pregnancy is well recognized, little is known about the influence of pregnancy on the clinical evolution and prognosis of different pre-existing chronic dermatological disorders.

SUMMARY

In this study a comprehensive search of the available literature and reviews has been undertaken in order to collect and analyze articles reporting pre-existing chronic skin disorders in pregnant women and report current knowledge on their particular clinical and therapeutic aspects.

Rhinitis 2020: A practice parameter update

This comprehensive practice parameter for allergic rhinitis (AR) and nonallergic rhinitis (NAR) provides updated guidance on diagnosis, assessment, selection of monotherapy and combination pharmacologic options, and allergen immunotherapy for AR. Newer information about local AR is reviewed. Cough is emphasized as a common symptom in both AR and NAR. Food allergy testing is not recommended in the routine evaluation of rhinitis. Intranasal corticosteroids (INCS) remain the preferred monotherapy for persistent AR, but additional studies support the additive benefit of combination treatment with INCS and intranasal antihistamines in both AR and NAR. Either intranasal antihistamines or INCS may be offered as first-line monotherapy for NAR. Montelukast should only be used for AR if there has been an inadequate response or intolerance to alternative therapies. Depot parenteral corticosteroids are not recommended for treatment of AR due to potential risks. While intranasal decongestants generally should be limited to short-term use to prevent rebound congestion, in limited circumstances, patients receiving regimens that include an INCS may be offered, in addition, an intranasal decongestant for up to 4 weeks. Neither acupuncture nor herbal products have adequate studies to support their use for AR. Oral decongestants should be avoided during the first trimester of pregnancy. Recommendations for use of subcutaneous and sublingual tablet allergen immunotherapy in AR are provided. Algorithms based on a combination of evidence and expert opinion are provided to guide in the selection of pharmacologic options for intermittent and persistent AR and NAR.

The Management of Nausea and Vomiting of Pregnancy: Synthesis of National Guidelines

Importance

Nausea and vomiting of pregnancy (NVP) affects a high proportion of the pregnant population.

Objective

The aim of this study was to compare and synthesize recommendations from national guidelines regarding the management of NVP.

Evidence Acquisition

A descriptive review of 3 recently published national guidelines on NVP was conducted: Royal College of Obstetricians and Gynaecologists on "The Management of Nausea and Vomiting of Pregnancy and Hyperemesis Gravidarum," American College of Obstetricians and Gynecologists on "Nausea and Vomiting of Pregnancy," and Society of Obstetricians and Gynaecologists of Canada on "The Management of Nausea and Vomiting of Pregnancy." These guidelines were summarized and compared in terms of the recommended management of pregnant women. The quality of evidence was also reviewed based on the method of reporting.

Results

Several differences were identified on the different guidelines regarding the management of NVP. Frequent small meals and avoidance of iron supplements are recommended for prevention. The consumption of ginger, acustimulations, antihistamines, phenothiazines, dopamine, and serotonin 5-hydroxytryptamine type 3 receptor antagonists is routinely recommended for use in the community as treatment.

Conclusions

Evidence-based medicine may lead to the adoption of an international guideline for the management of NVP, which may lead to a more effective management of that entity.

Desloratadine Use During Pregnancy and Risk of Adverse Fetal Outcomes: A Nationwide Cohort Study

BACKGROUND

Desloratadine is a frequently used drug for the treatment of allergic disorders, which often also require treatment during pregnancy. However, information on the fetal safety of desloratadine use during pregnancy is limited.

OBJECTIVE

To investigate the association between desloratadine use during pregnancy and adverse fetal outcomes.

METHODS

From a cohort of 1,287,668 pregnancies identified in the Danish nationwide registries in the study period 2001 to 2016, users of desloratadine and loratadine during pregnancy were matched in a 1:1 ratio based on propensity scores to compare the risk of adverse fetal outcomes. We compared the risk of the primary outcomes major birth defects (among a total of 3348 pregnancies) and spontaneous abortion (5498 pregnancies) and the secondary outcomes preterm birth (5280 pregnancies), small size for gestational age (SGA) for birth weight (5436 pregnancies), and stillbirth (6776 pregnancies). Logistic regression was used to estimate the prevalence odds ratio (OR) of major birth defects, preterm birth, and SGA, and Cox regression to estimate the hazard ratio (HR) of spontaneous abortion and stillbirth. Sensitivity analyses included comparing with cetirizine use in pregnancy and with pregnancies unexposed to desloratadine but with prior use as additional comparator groups.

RESULTS

Use of desloratadine in pregnancy was not associated with a significant increased risk of major birth defects (prevalence OR, 1.07; 95% confidence interval [CI], 0.77-1.50), spontaneous abortion (HR, 1.15; 95% CI, 0.96-1.37), preterm birth (prevalence OR, 0.84; 95% CI, 0.67-1.05), SGA (prevalence OR, 0.97; 95% CI, 0.80-1.16), or stillbirth (HR, 0.91; 95% CI, 0.31-2.70) compared with loratadine use in pregnancy. Sensitivity analyses, including those with the use of additional comparator groups, showed similar results.

CONCLUSION

Use of desloratadine during pregnancy was not associated with a statistically significant increased risk of adverse fetal outcomes as compared with loratadine. Results indicate that the fetal safety profile of desloratadine is similar to the currently recommended second-generation antihistamines during pregnancy.

The Management of Nausea and Vomiting of Pregnancy

OBJECTIVES

To review the evidence-based management of nausea and vomiting of pregnancy and hyperemesis gravidarum.

EVIDENCE

MEDLINE and Cochrane database searches were performed using the medical subject headings of treatment, nausea, vomiting, pregnancy, and hyperemesis gravidarum. The quality of evidence reported in these guidelines has been described using the Evaluation of Evidence criteria outlined in the Report of the Canadian Task Force on Preventative Health Care.

BENEFITS

Nausea and vomiting of pregnancy has a profound effect on women's health and quality of life during pregnancy as well as a financial impact on the health care system, and its early recognition and management is recommended. COST: Costs, including hospitalizations, additional office visits, and time lost from work, may be reduced if nausea and vomiting in pregnancy is treated early.

RECOMMENDATIONS

Multidisciplinary Management of Breast Cancer During Pregnancy

BACKGROUND

Although breast cancer during pregnancy (BCDP) is rare (occurring with only 0.4% of all BC diagnoses in female patients aged 16-49 years), management decisions are challenging to both the patient and the multidisciplinary team.

MATERIALS AND METHODS

Experts in breast cancer at the University of North Carolina conducted a targeted literature search regarding the multidisciplinary treatment approaches to BCDP: medical, surgical, and radiation oncology. Supportive care, including antiemetic agents, and imaging approaches were also reviewed.

RESULTS

Review of the literature revealed key points in the management of BCDP. Surgical management is similar to that in nonpregnant patients; pregnant patients may safely undergo breast-conserving surgery. Recommendations should be tailored to the individual according to the clinical stage, tumor biology, genetic status, gestational age, and personal preferences. Anthracycline-based chemotherapy can be safely initiated only in the second and third trimesters. The rate of congenital abnormalities in children exposed to chemotherapy is similar to the national average (approximately 3%). Dosing of chemotherapy should be similar to that in the nonpregnant patient (i.e., actual body surface area). Antihuman epidermal growth factor receptor 2 therapy, radiation, and endocrine treatment are contraindicated in pregnancy and lactation. Care should include partnership with obstetricians. The literature regarding prognosis of BCDP is mixed.

CONCLUSION

To maximize benefit and minimize risk to the mother and fetus, an informed discussion with the patient and her medical team should result in an individualized treatment plan, taking into account the timing of the pregnancy and the stage and subtype of the breast cancer. Because BCDP is rare, it is essential to collect patient data in international registries. The Oncologist 2017;22:324-334 IMPLICATIONS FOR PRACTICE: Breast cancer during pregnancy is a major ethical and professional challenge for both the patient and the multidisciplinary treatment team. Although the oncologic care is based on that of the non-pregnant breast cancer patient, there are many challenges from regarding the medical, surgical and radiation oncology and obstetrical aspects of care that need to be considered to deliver the safest and best treatment plan to both the mother and developing fetus.

Nausea and vomiting of pregnancy - What's new?

Nausea and vomiting of pregnancy (NVP) is one of the most common disorders of pregnancy. The symptoms occur predominantly during the first trimester, although in a subgroup of patients they can continue throughout the entire pregnancy and can affect the woman's quality of life. A small percentage of women develop a severe form of NVP called hyperemesis gravidarum (HG) that if left untreated may lead to significant maternal morbidity and adverse birth outcomes. Overall, the morbidity in pregnant women with NVP is significant, although it tends to be underestimated. The pathogenesis of NVP remains unclear, but there is consensus that the disorder is multifactorial and that various genetic, endocrine and infectious factors may be involved. The treatment of NVP can be challenging as the optimal targets for therapy are not known. Currently, the therapy used depends on the severity of the disorder and it is focused on improving the symptoms while minimizing risks to mother and fetus. Therapies range from dietary changes, pharmacologic treatment or hospitalization with intravenous fluid replacement and nutrition therapy. The aims of this review are 1) to provide an overview of NVP, 2) to present possible links between the most important factors associated with the pathogenesis of NVP and 3) to discuss the effectiveness and safety of the pharmacologic and non-pharmacologic options available to treat this disorder.

Allergic rhinitis: pharmacotherapy in pregnancy and old age

INTRODUCTION

Allergic rhinitis (AR) affects 20-30% of women in reproductive age and may worsen during pregnancy. About 10% of the elderly suffer from AR, and it could be under-diagnosed in these patients. Many drugs are currently available, however AR treatment during pregnancy and old age represents a challenging issue.

AREAS COVERED

A review of the literature on the topic has been performed. Expert commentary: In pregnancy, drug avoidance should be carefully balanced with the need for AR optimal control. Topical drugs are suggested as a first approach. The safety and tolerability profile of second-generation antihistamines is well supported. If allergen immunotherapy (AIT) is ongoing and well tolerated, there is no reason for stopping it. AIT initiation in pregnancy is not recommended. For elderly patients, no specific concerns have been highlighted regarding topical treatments, except from nasal decongestionants. Second generation antihistamines are generally well tolerated. Old age should not preclude AIT.

International Union of Basic and Clinical Pharmacology. XCVIII. Histamine Receptors

Histamine is a developmentally highly conserved autacoid found in most vertebrate tissues. Its physiological functions are mediated by four 7-transmembrane G protein-coupled receptors (H1R, H2R, H3R, H4R) that are all targets of pharmacological intervention. The receptors display molecular heterogeneity and constitutive activity. H1R antagonists are long known antiallergic and sedating drugs, whereas the H2R was identified in the 1970s and led to the development of H2R-antagonists that revolutionized stomach ulcer treatment. The crystal structure of ligand-bound H1R has rendered it possible to design new ligands with novel properties. The H3R is an autoreceptor and heteroreceptor providing negative feedback on histaminergic and inhibition on other neurons. A block of these actions promotes waking. The H4R occurs on immuncompetent cells and the development of anti-inflammatory drugs is anticipated.

Towards in vitro DT/DNT testing: Assaying chemical susceptibility in early differentiating NT2 cells

Human pluripotent embryonal carcinoma (NT2) cells are increasingly considered as a suitable model for in vitro toxicity testing, e.g. developmental toxicity and neurotoxicity (DT/DNT) studies, as they undergo neuronal differentiation upon stimulation with retinoic acid (RA) and permit toxicity testing at different stages of maturation. NT2 cells have recently been reported to show specific changes in dielectric resistance profiles during differentiation which can be observed as early as 24h upon RA-stimulation. These observations suggest altered susceptibility to chemicals at an early stage of differentiation. However, chemical susceptibility of early differentiating NT cells has not yet been studied. To address this question, we have established a cell fitness screening assay based on the analysis of intracellular ATP levels and we applied the assay in a large-scale drug screening experiment in NT2 stem cells and early differentiating NT2 cells. Subsequent analysis of ranked fitness phenotypes revealed 19 chemicals with differential toxicity profile in early differentiating NT2 cells. To evaluate whether any of the identified drugs have previously been associated with DT/DNT, we conducted a literature search on the identified molecules and quantified the fraction of chemicals assigned to the FDA (Food and Drug Administration) pregnancy risk categories (PRC) N, A, B, C, D, and X in the hit list and the small molecule library. While the fractions of the categories N and B were decreased (0.81 and 0.35-fold), the classes C, D and X were increased (1.35, 1.47 and 3.27-fold) in the hit list compared to the chemical library. From these data as well as from the literature review, identifying large fractions of chemicals being directly (∼42%) and indirectly associated with DT/DNT (∼32%), we conclude that our method may be beneficial to systematic in vitro-based primary screening for developmental toxicants and neurotoxicants and we propose cell fitness screening in early differentiating NT2 cells as a strategy for evaluating chemical susceptibility at different stages of differentiation to reduce animal testing in the context of the 3Rs.