Hypersensitivity reactions to antiepileptic drugs in children.

BACKGROUND: Antiepileptic drugs (AEDs) can cause hypersensitivity reactions in children. These reactions are mainly cutaneous, self-limiting, and benign, but life-threatening severe cutaneous adverse reactions can occur. Infections can lead to skin eruptions and mimic drug hypersensitivity reactions, if a drug is taken at the same time. The aims of our study were to confirm or rule out the diagnosis of hypersensitivity reactions to AEDs in children and to detect an infection which mimics these reactions. METHODS: A prospective survey was conducted in a group of 100 children with histories of hypersensitivity reactions to AEDs by performing patch tests, delayed-reading intradermal test, and, in case of negative results, challenge test. In all children, a study was performed to detect infections by viruses or Mycoplasma pneumoniae. RESULTS: Maculopapular exanthema and delayed-appearing urticaria were the most reported hypersensitivity reactions to AEDs. Sixty-six (66%) of 100 children had confirmed hypersensitivity reactions to AEDs. Fifty-nine children had positive patch test. No children had positive challenge tests. The most common AEDs causing hypersensitivity reactions were carbamazepine (45.4%) and lamotrigine (43.6%). Thirty-two children had positive tests for viruses or M pneumoniae, and nine of them had also a positive allergy work-up. CONCLUSION: Considering that there are no specific tests to distinguish between a viral infection and hypersensitivity reactions to AEDs in the acute phase, a diagnostic work-up should be performed in all children with suspected hypersensitivity reactions to AEDs, as well as infectious agent study, to remove a false label of hypersensitivity.

The Frequency and Clinical Features of Hypersensitivity Reactions to Antiepileptic Drugs in Children: A Prospective Study.

BACKGROUND: Antiepileptic drugs (AEDs) can cause hypersensitivity reactions during childhood. Studies report a wide clinical spectrum of reactions with AED use, ranging from a mild rash to severe cutaneous reactions. OBJECTIVE: To determine the prevalence and clinical features of AED hypersensitivity reactions during childhood. METHODS: Patients in our pediatric neurology clinic who were prescribed an AED for the first time between November 2015 and November 2016 were monitored and those who developed skin rash during this period were evaluated. RESULTS: A total of 570 patients were evaluated. The median age of the patients was 8.86 (interquartile range, 4.2-13.7) years, and 55.8% (318) of patients were male. The most frequently used AEDs were valproic acid (42%, n = 285) and carbamazepine (20.4%, n = 116). Hypersensitivity reactions to AEDs developed in 5.4% of patients. Of these patients, 71% (29) had cutaneous drug reactions and 29% (9) had severe cutaneous drug reactions; 61.3% (19) were using aromatic AEDs, and the leading suspected AED was carbamazepine (45.2%). Comparison of patients who did and did not develop AED hypersensitivity showed that hypersensitivity was more frequent among patients who were younger than 12 years, who used aromatic AEDs, or who used multiple AEDs. In addition, according to regression analysis results, aromatic AED use significantly increased the risk of AED hypersensitivity (P < .001). CONCLUSIONS: Although allergic reactions to AEDs are rare, they are of significance because they can cause life-threatening severe cutaneous drug reactions. Therefore, patients receiving AEDs, especially aromatic AEDs, must be monitored closely.

Application of in Vitro T Cell Assay Using Human Leukocyte Antigen-Typed Healthy Donors for the Assessment of Drug Immunogenicity.

It is unclear whether priming of naïve T cells to drugs is detectable in healthy human donors expressing different human leukocyte antigen (HLA) alleles. Thus, we examined T cell priming with drugs associated with HLA risk alleles and control compounds in 14 HLA-typed donors. Nitroso sulfamethoxazole and piperacillin activated T cells from all donors, whereas responses to carbamazepine and oxypurinol were only seen in donors expressing HLA-B*15:02 and HLA-B*58:01, respectively. Weak flucloxacillin-specific T cell responses were detected in donors expressing HLA-B*57:01 and HLA-B*58:01. These data show that the priming of T cells with certain drugs is skewed toward donors expressing specific HLA alleles.

Patch testing in a case of eslicarbazepine and carbamazepine induced cutaneous reaction.

Summary: Anticonvulsants are among the drugs most commonly involved in cutaneous adverse drug reactions (CADRs). Eslicarbazepine is a new anti-epileptic drug, chemically related to carbamazepine but with a more favorable safety profile. We report the clinical case of a woman who developed a skin rash on day 10 of eslicarbazepine with further exacerbation with eosinophilia on day 2 of carbamazepine. Epicutaneous tests were positive with eslicarbazepine.

Cutaneous drug reactions to antiepileptic drugs and relation with HLA alleles in the Turkish population.

Summary: Background and objective. Many studies have shown associations between HLAB*15:02, HLA-A*31:01 and carbamazepine (CBZ)-induced delayed cutaneous hypersensitivity reactions. The aim of this study is to evaluate a possible association between delayed cutaneous reactions to antiepileptic drugs (AEDs) and certain HLA-A and HLA-B alleles in the Turkish population. Methods. The study consisted of 3 groups: Group I (reactive group) included the patients who had documented delayed cutaneous reactions to any antiepileptic drug. Group II (non-reactive group) included the patients who have been on antiepileptic treatment at least for three months without any adverse reactions. Group III consisted of healthy subjects. The HLA-A and B alleles were analyzed in all groups. Results. Forty patients (29 female) had experienced different hypersensitivity reactions due to AEDs: maculopapular exanthema (26 patients), Stevens-Johnson syndrome (6 patients), drug rash with eosinophilia and systemic symptoms (7 patients), toxic epidermal necrolysis (1 patient). Lamotrigine (11) and CBZ (10) were the most common culprit drugs involved in the reactions. The HLA-B*15:02 was not present in any of the study groups. However, HLA-B*35:02 was found in 4 patients from the reactive group, while it was not observed in non-reactive patients and was detected in only one healthy subject (p = 0.021). Conclusion. Although our preliminary results did not indicate a strong allele association with AED hypersensitivity, HLA-B*35:02 appears to be a candidate allele for MPE / DRESS / DIHSS induced by AED's in Turkish population. Further studies with a larger sample size may result in more comprehensive data about the genetic tendency for AED hypersensitivity in the Turkish population.

The use of patch tests in the diagnosis of delayed hypersensitivity drug eruptions.

BACKGROUND: Adverse drug reactions (ADRs) are common. In the absence of a sufficiently sensitive and specific laboratory test, identification of the culprit drug remains a diagnostic challenge. Patch tests have recently been advocated as a means of detecting drug sensitivity. OBJECTIVE: To further elucidate the usefulness of patch tests in revealing the causative drugs of cutaneous ADRs (CADRs). MATERIALS AND METHODS: We conducted a non-blinded, prospective, controlled clinical trial. Twenty-five patients with a history of CADRs were patch tested, and 25 healthy subjects who had never experienced CADRs served as controls. RESULTS: A morbilliform eruption was the most frequent skin reaction. Patch tests were positive in eight of the 25 patients with CADR (32%). Specifically, five of the 13 patients with morbilliform drug eruption (38.4%) tested positive, as did one of the four patients with erythema multiforme/Stevens-Johnson syndrome (25%), and one of the two patients with the drug reaction with eosinophilia and systemic symptoms syndrome. Antibiotics and anticonvulsants resulted in positive patch tests most often. Patch test sensitivity was 32%, specificity was 92%, and negative and positive predictive values were 57.5% and 80%, respectively. Significant correlation was found between the patch test result and the clinical probability of a CADR according to the imputability score of the drug. CONCLUSIONS: Patch testing for drugs causing ADRs shows high specificity rates even though the sensitivity is low. Such tests may therefore be useful in supporting the diagnosis of delayed-type CADRs, particularly when antibiotics or anticonvulsants are involved and the cutaneous reaction is a morbilliform rash.

Research on Susceptible Genes and Immunological Pathogenesis of Cutaneous Adverse Drug Reactions in Chinese Hans.

Cutaneous adverse drug reactions (cADRs) include mild maculopapular exanthems (MPE), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS) and acute generalized exanthematous pustulosis (AGEP). We used HLA high-resolution genotyping and genome wide association analysis (GWAS) to identify the genetic markers for cADRs induced by common culprit drugs in Han Chinese population. To further understand the immunopathogenesis of cADRs, and with the goal of developing treatment strategies, we compared the expression of cytoxic cytokines between the patients with cADRs and normal controls. Our data suggested that the carbamazepine induced SJS/TEN, allopurinol induced CADRs, methazolamide induced SJS/TEN and SASP induced DRESS were respectively strongly associated with HLA-B*15:02, HLA-B*58:01, HLA-B*59:01 and HLA-B*13:01. In addition, increased expression of cytotoxic cytokines in sera and tissues of cADRs patients were found, compared with healthy controls. Our findings may shed light on prediction and prevention of cADRs, provide clues to pathogenesis, and guide treatment strategies of these reactions.

Drug reaction with eosinophilia and systemic symptoms syndrome is not uncommon and shows better clinical outcome than generally recognised.

BACKGROUND: Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare disease which can cause severe morbidity and mortality. The aim of this study is to evaluate the clinical manifestation and course of DRESS syndrome. METHODS: We conducted a retrospective analysis of prospectively collected data in 45 patients with DRESS syndrome diagnosed between September 2009 and August 2011. RESULTS: The most common causative drug group was antibiotics (n=13, 28.9%), followed by anticonvulsants (n=12, 26.7%), antituberculosis drugs (n=6, 13.3%), non-steroidal anti-inflammatory drugs (n=4, 8.9%), undetermined agents (n=4, 8.9%), allopurinol (n=3, 6.7%), and others (n=3, 6.7%). The latency period ranged from 2 to 120 days, with a mean of 20.2 ± 24.3 days. The longest latency period was noted for the antituberculosis drug group, at 46.5 ± 29.9 days. Eosinophilia in peripheral blood examination was noted in 35 subjects (77.8%). Atypical lymphocytosis was noted in 16 patients (35.6%), and thrombocytopenia in seven patients (15.6%). Hepatic involvement was noted in 39 (86.7%) study patients, kidney in eight (17.8%), lung in four (8.9%), and central nervous system in one (2.3%). Systemic corticosteroids were administered to 10 patients (22.2%). Forty-three patients (95.6%) showed complete recovery, while two patients had poor outcomes. CONCLUSIONS: DRESS syndrome was not more uncommon than generally recognised. Antibiotics were the most frequently implicated drug group, followed by anticonvulsants. Most patients with this disease showed a better clinical outcome than that which had been generally expected.

Human leukocyte antigen genotypes and trial of desensitization in patients with oxcarbazepine-induced skin rash: a pilot study.

BACKGROUND: Skin rash associated with specific antiepileptic drugs occurs not infrequently and it usually necessitates discontinuation of the causative drugs. An alternative strategy is to desensitize the individual to the offending drug. We checked the human leukocyte antigen genotypes and conducted a pilot study to investigate the usefulness and safety of desensitization in pediatric patients with skin rash associated with oxcarbazepine. METHODS: We enrolled 19 patients with epilepsy who had discontinued oxcarbazepine because of skin rash despite an initial good response and then became refractory to other antiepileptic drugs along with an individual with paroxysmal kinesigenic dyskinesia with a similar situation. High-resolution HLA-A and -B genotyping was performed to investigate the genetic risk. The desensitization began with 0.1 mg daily reaching 120 mg on the thirty-first day. Thereafter, the dose was increased at a rate of 12 mg/day. RESULTS: Nineteen patients completed the desensitization protocol to a target dosage over 2-5 months. Five patients developed itching and erythema during desensitization, but the symptoms disappeared after withholding a dose increment transiently. There were no human leukocyte antigen genotypes relevant to aromatic antiepileptic drug-induced severe hypersensitivity reactions. The seizure frequency was reduced to less than at baseline in 18 individuals. CONCLUSION: This study demonstrated 95% efficacy, including 42% seizure-free patients and the favorable tolerability of desensitization to oxcarbazepine in patients with intractable epilepsy and one patient with paroxysmal kinesigenic dyskinesia. Screening for sensitive human leukocyte antigen types and exclusion of severe hypersensitivity reactions should precede desensitization.

T-cell receptor and carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis: understanding a hypersensitivity reaction.

Ample evidence exists to support the view that drug hypersensitivity is mediated by adaptive immunity, which involves MHC-restricted drug presentation, activation and clonal expansion of T cells. The specific MHC molecules implicated in hypersensitivity have been identified; for example, HLA-B*5701 in abacavir-induced drug hypersensitivity and HLA-B*1502 in carbamazepine-induced Stevens-Johnson syndrome. However, little is known about the role of drug-specific T cells and their T-cell receptors (TCRs) in the pathogenesis of drug hypersensitivity. Using the combination of a strong HLA-B*1502 predisposition in carbamazepine-induced Stevens-Johnson syndrome and applying global analysis of the TCR repertoire, restricted and common TCR usage in the development of severe drug hypersensitivity have recently been documented. This article reviews recent advances in the understanding of the pathogenic role of drug-specific T cells and their TCRs in the development of drug hypersensitivity and provides an analysis of their potential clinical implications.

Reactivity of commercial benzodiazepine immunoassays to phenazepam.

Phenazepam is a long acting benzodiazepine that is not controlled in Canada, the United States or many European countries. The abuse of phenazepam has gained recent attention due to the number of hospitalizations and fatalities resulting from overdose. The compound is relatively potent with recommended doses of 0.5-1.0 mg, or 1/10th the recommended dose of diazepam, and is easy to obtain locally or from international suppliers via the internet. Increased risk of phenazepam overdose is attributed to its potency and the forms in which it is supplied. Individuals without scales or balances are prone to estimate dose amounts of powder visually, which can result in significant errors. The detection of phenazepam has been described using various methods including GC, GC/MS and LC/MS, but no data regarding the sensitivity of commercially available immunoassays exist. In this study, phenazepam-spiked urine samples were analyzed using five commercial instruments and two point of care devices. The concentrations of phenazepam required for detection ranged from 140-462 ng/mL, which is comparable to those of other benzodiazepines. Laboratorians and clinicians should be confident that phenazepam will be detected via most commercial drugs of abuse screens in patients after significant ingestion.

HLA-A31 strongly associates with carbamazepine-induced adverse drug reactions but not with carbamazepine-induced lymphocyte proliferation in a Japanese population.

Carbamazepine (CBZ) is the most frequent culprit drug for severe cutaneous adverse drug reactions (ADR), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) and drug-induced hypersensitivity syndrome (DIHS). A strong association between human leukocyte antigen (HLA)-B*1502 and CBZ-induced SJS/TEN has been reported in Han Chinese, Thai, Malaysian and Indian populations, but not in Caucasian or Japanese populations. Recent studies showed an association between HLA-A*3101 and CBZ-induced ADR in Caucasian and Japanese populations. We conducted a case-control study to determine HLA genotyping of patients with CBZ-induced ADR in a Japanese population. Fifteen patients with CBZ-induced ADR and 33 subjects who had taken CBZ for more than 3 months without evidence of any ADR as a control were enrolled. In addition, the results of a CBZ-induced lymphocyte stimulation test were compared between the groups. A strong association was found between HLA-A31 and CBZ-induced ADR (P < 0.001), and a weak association was found between HLA-A11 and HLA-B51 with CBZ-induced ADR. No HLA-B*1502 was found in either patients or control subjects. The mean CBZ-induced lymphocyte stimulation index was significantly high in patients with CBZ-induced ADR compared with CBZ-tolerant patients (P < 0.001); however, no significant difference was seen between HLA-A31-positive subjects and HLA-A31-negative subjects in either group. These findings suggest that HLA-A31 is strongly associated with CBZ-induced ADR in the Japanese, but does not determine CBZ-induced lymphocyte proliferation.

Safety assessment in pediatric studies.

It typically takes many years before an association of a drug with a rare, serious adverse reaction is established. As related to pediatric drug use, evidence is even more erratic, as most drugs are used off labels. To enhance child safety, there is an urgent need to develop robust and rapid methods to identify such associations in as timely a manner as possible. In this chapter, several novel methods, both clinically based pharmacoepidemiological approaches and laboratory-based methods, are described.

Antiepileptic drugs and the immune system.

Data on the effects of antiepileptic drugs on the immune system are frequently inconsistent and sometimes conflicting because the effects of drugs cannot be separated from those of seizures, first-generation drugs have been most intensively investigated, the patient's genetic background, the mechanism of action and the pharmacokinetic profile of AEDs and the concurrent use of immunosuppressant drugs may act as confounders. Valproate, carbamazepine, phenytoin, vigabatrin, levetiracetam, and diazepam have been found to modulate the immune system activity by affecting humoral and cellular immunity. AEDs are associated with pharmacokinetic interactions (most frequently occurring with carbamazepine, phenytoin, phenobarbital and valproate). Hepatic metabolism is the primary site of interaction for both AEDs and immunotherapies (ACTH, dexamethasone, hydrocortisone, methylprednisolone, cyclophosphamide, methotrexate, rituximab), which entail induction or inhibition of drug effects. However, the clinical importance of these drug interactions is still far from defined. An important adverse effect of the action of AEDs on the immune system is antiepileptic hypersensitivity syndrome (AHS), a life-threatening, idiosyncratic cutaneous reaction to aromatic AEDs resulting in end organ damage. Phenytoin, carbamazepine, phenobarbital, lamotrigine, oxcarbazepine, felbamate, and zonisamide have been implicated. The pathogenic mechanisms of AHS are incompletely understood.

Development of a dot-blot assay for screening monoclonal antibodies to low-molecular-mass drugs.

Dot-blot is a versatile and simple analysis to perform. We adapted this method as a simple identity test for monoclonal antibodies to a number of small compounds: three transplant drugs, an anticonvulsant, a steroid, an anticancer drug, and an antibiotic. Immunology-based identity tests using low-molecular-mass organic compounds have historically been a challenge to develop. We modified the traditional dot-blot assay to serve as an identity test for monoclonal antibodies to carbamazepine, sirolimus, tacrolimus, cyclosporine, cortisol, methotrexate, and gentamicin. The primary obstacle was the immobilization of these organic compounds on nitrocellulose as nitrocellulose is also soluble in most of the organic solvents in which the compounds are soluble. We evaluated different membranes, solvents, and chemical forms of these organic compounds to overcome this challenge. A number of incubation and washing solutions were also investigated. By varying the chemical form, concentration, and incubation conditions, a set of effective and reproducible identity tests were developed for these monoclonal antibodies.

Hypersensitivity syndrome induced by anticonvulsants: possible cross-reactivity between carbamazepine and lamotrigine.

A 14-year-old male presents with erythroderma and fever 44 days after carbamazepine intake. Laboratory exams show eosinophilia and elevated liver enzymes, and thoracic imaging reveals interstitial pneumonitis. All symptoms disappear after carbamazepine withdrawal. A patch test to carbamazepine performed 6 weeks after recovery is positive. About 8 months later, the patient exhibits the same clinical and biological picture 52 days after lamotrigine intake. Lamotrigine is stopped and all symptoms disappear. A patch test to LMG is positive. This case illustrates a possible cross-reactivity between carbamazepine and lamotrigine, which are aromatic and nonaromatic anticonvulsants, respectively.