Anticonvulsant hypersensitivity syndrome: a review

Case report: Interstitial pneumonitis after initiation of lamotrigine

The second-generation anticonvulsant lamotrigine is widely used in the psychiatric field as a mood stabilizer or antidepressant augmentation therapy. Although particularly older anticonvulsants are known for their potential to cause hypersensitivity syndromes, newer antiepileptic drugs do hold a certain risk as well. Presenting a case of a 32-year-old male inpatient of African ethnicity suffering from a primary severe depressive episode in the course of a recurrent major depressive disorder, we report the occurrence of a rapid-onset drug-induced pneumonitis. Herewith, the interstitial pneumonitis occurred after the initiation of 25 mg lamotrigine as an augmentation therapy. Except for the clear temporal correlation between the administration of lamotrigine and the onset of pneumonitis, we did not reveal any further potentially causal diagnostic hints. Importantly, no relevant genetic variations of metabolizing enzymes or drug interactions resulting in lamotrigine overdosage as a potential cause of toxicity were identified. Our experience with a potentially life-threatening adverse drug reaction shortly after the initiation of the largely well-tolerated lamotrigine suggests a potential side effect under the second-generation anticonvulsant although similar adverse events are deemed to be very rare.

Severe cutaneous adverse reaction associated with antiseizure medications: Diagnosis, management, and prevention

Severe cutaneous adverse reactions (SCARs) are potentially life-threatening, with considerable morbidity and mortality. They are nonimmediate hypersensitivity reactions that occur in specifically predisposed patients with delayed T-cell-mediated hypersensitivity reaction. Antiseizure medications (ASMs) are among the drugs that can induce SCAR. Increased awareness of SCAR among clinicians treating patients with ASMs is critically important for early recognition of symptoms, prompt identification and removal of the causal drug, and early intervention to reduce SCAR-related acute and long-term morbidity and mortality. The diagnosis, management, and prevention of Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS) are reviewed, along with the current understanding of the pathomechanisms and role of genetics in SCAR development. Supportive care and immunomodulating treatments for SCAR are discussed.

Cenobamate (YKP3089) as adjunctive treatment for uncontrolled focal seizures in a large, phase 3, multicenter, open-label safety study

Objective

During the development of cenobamate, an antiseizure medication (ASM) for focal seizures, three cases of drug reaction with eosinophilia and systemic symptoms (DRESS) occurred. To mitigate the rate of DRESS, a start‐low, go‐slow approach was studied in an ongoing, open‐label, multicenter study. Also examined were long‐term safety of cenobamate and a method for managing the pharmacokinetic interaction between cenobamate, a 2C19 inhibitor, and concomitant phenytoin or phenobarbital.

Methods

Patients 18‐70 years old with uncontrolled focal seizures taking stable doses of one to three ASMs were enrolled. Cenobamate 12.5 mg/d was initiated and increased at 2‐week intervals to 25, 50, 100, 150, and 200 mg/d. Additional biweekly 50 mg/d increases to 400 mg/d were allowed. During titration, patients taking phenytoin or phenobarbital could not have their cenobamate titration rate or other concomitant ASMs adjusted; phenytoin/phenobarbital doses could be decreased by 25%‐33%.

Results

At data cutoff (median treatment duration = 9 months), 1347 patients were enrolled, of whom 269 (20.0%) discontinued, most commonly due to adverse events (n = 137) and consent withdrawn for reason other than adverse event (n = 74); 1339 patients received ≥1 treatment dose (median modal dose = 200 mg). The most common treatment‐emergent adverse events (TEAEs) were somnolence (28.1%), dizziness (23.6%), and fatigue (16.6%). Serious TEAEs occurred in 108 patients (8.1%), most commonly seizure (n = 14), epilepsy (n = 5), and pneumonia, fall, and dizziness (n = 4 each). No cases of DRESS were identified. In the phenytoin/phenobarbital groups, 43.4% (36/114) and 29.7% (11/51) of patients, respectively, had their doses decreased. At the end of titration, mean plasma phenytoin/phenobarbital levels were generally comparable to baseline.

Significance

No cases of DRESS were identified in 1339 patients exposed to cenobamate using a start‐low (12.5 mg/d), go‐slow titration approach. Cenobamate was generally well tolerated in the long term, with no new safety issues found. Phenytoin/phenobarbital dose reductions (25%‐33%), when needed during cenobamate titration, maintained stable plasma levels.

Severe Cutaneous Adverse Reactions to Antiepileptic Drugs: A Nationwide Registry-Based Study in Korea

PURPOSE

Severe cutaneous adverse reactions (SCARs), including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS) to antiepileptic drug (AED), are rare, but result in significant morbidity and mortality. We investigated the major culprit drugs, clinical characteristics, and clinical course and outcomes of AED-induced SCARs using a nationwide registry in Korea.

METHODS

A total of 161 patients with AED-induced SCARs from 28 referral hospitals were analyzed. The causative AEDs, clinical characteristics, organ involvements, details of treatment, and outcomes were evaluated. We compared the clinical and laboratory parameters between SJS/TEN and DRESS according to the leading causative drugs. We further determined risk factors for prolonged hospitalization in AED-induced SCARs.

RESULTS

Carbamazepine and lamotrigine were the most common culprit drugs causing SCARs. Valproic acid and levetiracetam also emerged as the major causative agents. The disease duration and hospital stay in carbamazepine-induced SJS/TEN were shorter than those in other AEDs (P< 0.05, respectively). In younger patients, lamotrigine caused higher incidences of DRESS than other drugs (P= 0.045). Carbamazepine, the most common culprit drug for SCARs, was associated with a favorable outcome related with prolonged hospitalization in SJS (odds ratio, 0.12; 95% confidence interval, 0.02-0.63, P= 0.12), and thrombocytopenia was found to be a risk factor for prolonged hospitalization in DRESS.

CONCLUSION

This was the first large-scale epidemiological study of AED-induced SCARs in Korea. Valproic acid and levetiracetam were the significant emerging AEDs causing SCARs in addition to the well-known offending AEDs such as carbamazepine and lamotrigine. Carbamazepine was associated with reduced hospitalization, but thrombocytopenia was a risk factor for prolonged hospitalization. Our results suggest that the clinical characteristics and clinical courses of AED-induced SCARs might vary according to the individual AEDs.

Association between HLA gene polymorphism and cutaneous adverse reactions caused by antiepileptic drugs

The association between cutaneous adverse drug reactions (cADRs) caused by antiepileptic drugs (AEDs) and human leukocyte antigen-A (HLA-A) and HLA-B genes in Chinese Han population in Shanghai was investigated. Through the case-control study, 30 child patients with AED-induced cADRs (cADRs group), 60 AED-tolerant child patients (AED-tolerant group) and 60 normal children not taking AEDs (normal group) were collected. The HLA-B*15:02 and HLA-A*31:01 genotypes were detected using the polymerase chain reaction-sequence-specific oligonucleotide (PCR-SSO) probe method, and the correlation of HLA-B*15:02 and HLA-A*31:01 genes with the incidence of cADRs was analyzed. The positive rate of HLA-B*15:02 gene was 83.33% in the cADRs group, which was significantly increased compared with that in the AED-tolerant and normal groups (P<0.01). The positive rate of HLA-A*31:01 gene was 63.33% in the cADRs group, which was obviously increased compared with that in the AED-tolerant and normal groups (P<0.01). There were no significant differences in HLA-B*15:02 and HLA-A*31:01 genotypes between the AED-tolerant and normal groups (P>0.05). The results showed that HLA-B*15:02 and HLA-A*31:01 are significantly associated with cADRs in a Chinese Han population in Shanghai, suggesting that HLA-B*15:02 and HLA-A*31:01 genotypes should be detected in the application of AEDs.

Cutaneous Adverse Drug Reactions in Dogs Treated with Antiepileptic Drugs

Epilepsy is one of the most common neurologic disorders in dogs and life-long treatment with antiepileptic drugs (AED) is frequently required. Adverse events of AED targeting the skin are only rarely reported in veterinary medicine and the true incidence and spectrum of cutaneous reactions in epileptic dogs remains unknown. In this study, we hypothesized that cutaneous reactions commonly occur in epileptic dogs and are related to AED treatment. A retrospective case review of 185 dogs treated for epilepsy identified 20.0% with simultaneous appearance of dermatologic signs. In a subsequent prospective case investigation (n = 137), we identified newly appearing or distinct worsening of skin lesions following initiation of AED therapy in 10.9% of dogs treated for epilepsy (95% CI 6.8–17.7%). Cutaneous lesions were classified as probably drug-induced in 40.0% of these cases. Patch testing and intradermal testing were further investigated as potential diagnostic methods to confirm AED hypersensitivity. They were of high specificity but sensitivity and positive predictive value appeared inappropriate to recommend their routine use in clinical practice.

Bronchiolitis obliterans organising pneumonia associated with anticonvulsant hypersensitivity syndrome induced by lamotrigine

A 14-year-old girl who was known to have a seizure disorder and on lamotrigine treatment was admitted to the hospital, with a history of rash, fever and cough. Her condition deteriorated with clinical features suggestive of anticonvulsant hypersensitivity syndrome (ACHS) complicated with bronchiolitis obliterans organising pneumonia (BOOP). Her chest CT showed multifocal parenchymal opacities and lung biopsy was typical for BOOP. Initially, the lamotrigine was discontinued since the onset of the rash, then she was treated for pneumonia with antibiotics, which may have delayed the diagnosis. Eventually, BOOP was considered and she was treated with a high dose of corticosteroid. She improved clinically and her repeated chest CT showed a marked resolution of the lesions. This case illustrates the possible occurrence of BOOP as a complication of ACHS secondary to lamotrigine treatment.

[Anticonvulsant Hypersensitivity Syndrome: A Case Report]

DRESS syndrome (skin reaction with eosinophilia and systemic symptoms) is an idiosyncratic drug reaction characterized by rash, fever, lymphadenopathy, and internal organ dysfunction. This case report is on a patient with bipolar affective disorder who presented with a systemic inflammatory response associated with the use of valproic acid, and an important activation of symptoms when used with other drugs with a different pharmacological action mechanism. The diagnosis of DRESS syndrome is primarily by exclusion, and its detection may be difficult, which could potentially become fatal for the patient.

Absence of HLA-B*1502 and HLA-A*3101 alleles in 9 Korean patients with antiepileptic drug-induced skin rash: a preliminary study

There have been a number of studies about correlations between HLA genotypes in various ethnic groups and occurrence of various cutaneous adverse drug reactions, ranging in intensity from mild to severe, caused by antiepileptic drugs (AEDs). This is the first report analyzing the HLA genotypes of 9 Korean patients with skin rashes induced by various AEDs. The AEDs that induced skin rash were lamotrigine (n=3), carbamazepine (n=3), oxcarbazepine (n=1), phenobarbital (n=1), and phenytoin (n=1). None of the patients' HLA genotypes was either HLA-B^*1502 or HLA-A^*3101. Based on these series of cases, AED-induced skin rash can occur independently of HLA-B^*1502 or HLA-A^*3101 genotypes in the Korean patients.

Parietal lobe volume deficits in adolescents with schizophrenia and adolescents with cannabis use disorders

OBJECTIVE

In early-onset schizophrenia (EOS), the earliest structural brain volumetric abnormalities appear in the parietal cortices. Early exposure to cannabis may represent an environmental risk factor for developing schizophrenia. This study characterized cerebral cortical gray matter structure in adolescents in regions of interest (ROIs) that have been implicated in EOS and cannabis use disorders (CUD).

METHOD

T1-weighted magnetic resonance images were acquired from adolescents with EOS (n = 35), CUD (n = 16), EOS + CUD (n = 13), and healthy controls (HC) (n = 51). Using FreeSurfer, brain volume was examined within frontal, temporal, parietal and subcortical ROIs by a 2 (EOS versus no EOS) × 2 (CUD versus no CUD) design using multivariate analysis of covariance. In ROIs in which volumetric differences were identified, additional analyses of cortical thickness and surface area were conducted.

RESULTS

A significant EOS-by-CUD interaction was observed. In the left superior parietal region, both "pure" EOS and "pure" CUD had smaller gray matter volumes that were associated with lower surface area compared with HC. A similar alteration was observed in the comorbid group compared with HC, but there was no additive volumetric deficit found in the comorbid group compared with the separate groups. In the left thalamus, the comorbid group had smaller gray matter volumes compared with the CUD and HC groups.

CONCLUSIONS

These preliminary data indicate that the presence of a CUD may moderate the relationship between EOS and cerebral cortical gray matter structure in the left superior parietal lobe. Future research will follow this cohort over adolescence to further examine the impact of cannabis use on neurodevelopment.

Hla-B alleles and lamotrigine-induced cutaneous adverse drug reactions in the Han Chinese population

Lamotrigine (LTG) is a commonly used antiepileptic drug. However, the use of LTG is limited because of its cutaneous adverse drug reactions (cADRs) ranging from mild maculopapular eruption (MPE) to severe Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). A strong association between HLA-B*1502 and carbamazepine-induced SJS/TEN has been identified in Chinese and Thai. Although three of seven cases with HLA-B*1502 have been reported in LTG-induced SJS/TEN so far, the relationship between HLA-B*1502 and LTG-induced SJS/TEN needs further investigation. It is also unclear whether there is a specific genetic marker associated with LTG-induced MPE in Chinese. In this study, we genotyped 43 Han Chinese patients treated with LTG (14 cases with LTG-induced cADRs and 29 LTG-tolerant controls), using PCR-SSP for HLA-B*1502 testing and low-resolution genotyping, as well as sequencing for four-digit genotyping. The two cases with SJS were negative for HLA-B*1502, with B1301/1301 and 4601/5610, respectively. Combining the data with previous studies, there was no significant difference in the frequency of subjects with HLA-B*1502 between the LTG-induced SJS/TEN group and the LTG-tolerant group (p = 0.08, OR 4.23, 95% CI 0.94-18.97). In the MPE group, only one was positive for HLA-B*1502. There was no significant difference in the frequency of a specific HLA-B allele between the MPE group and the LTG-tolerant group either. In this study, no significant association between HLA-B*1502 and LTG-induced SJS or MPE was found. Given the small sample size and only HLA-B locus genotyping, further large-scale studies are required to explore genetic associations with LTG-induced cADRs.

Pilot association study of oxcarbazepine-induced mild cutaneous adverse reactions with HLA-B*1502 allele in Chinese Han population

BACKGROUND

Recent study demonstrated that HLA-B*1502 was a common risk allele in aromatic antiepileptic drugs (AEDs) induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Han Chinese. However, the association of AEDs-induced mild maculopapular eruption (MPE) with HLA-B*1502 remains unclear until recently. In the present study, we conducted a pilot study to detect a possible association of oxcarbazepine (OXC)-induced MPE with HLA-B*1502 allele in Chinese Han population.

METHODS

We enrolled 90 subjects involving 9 patients with OXC-induced MPE and two groups of controls, 9 OXC-tolerant and 72 normal controls. High-resolution HLA genotyping was performed by specific kit. The results of HLA genotyping are expressed as positive or negative for HLA-B*1502 allele. Differences in genotype frequencies between groups were assessed by the Fisher's exact test.

RESULTS

Four cases were detected as positive for HLA-B*1502 amongst 9 patients. However, only 1 subject was positive amongst 9 tolerant controls, and 6 subjects were positive amongst 72 normal controls. The difference in HLA-B*1502 allele frequencies between the MPE group and normal controls was statistically significant (OR: 8.8; 95% CI: 1.853-41.790; P=0.011). In addition, we also observed an increased frequency of HLA-B*1502 allele in patients (44.44%) compared with tolerant controls (11.11%), although it failed to reach statistical significance (P=0.294).

CONCLUSIONS

Our findings indicate that HLA-B*1502 allele may contribute to the genetic susceptibility to OXC-induced MPE in Chinese Han population. In order to safer AEDs use, we recommend that HLA-B*1502 allele should be tested for patients with OXC-induced MPE before changing to other AEDs, and AEDs with similar chemical structure should be avoided in individuals who test positive for HLA-B*1502 allele. It should be pointed out that, however, our results may well be just by chance owing to the small sample size and should be further confirmed in future studies.

Amoxicillin-Induced Hypersensitivity After DRESS To Carbamazepine

The anticonvulsant hypersensitivity syndrome, also known as drug rash eosinophilia and systemic symptoms (DRESS), is a rare but severe form of adverse cutaneous reaction. Several aromatic anticonvulsant drugs, such as carbamazepine (CBZ), phenytoin, or phenobarbital have been frequently associated with the onset of DRESS. Cross-reactivity among the aromatic anticonvulsants frequently occurs (40 to 80% of patients). However, cross reactivity with other drugs such as betalactams have exceptionally been reported. We report a clinical observation describing a DRESS associated with CBZ with a subsequent hypersensitivity to amoxicillin (AMX). A 34-year-old male with a 20-year history of epilepsy was treated with valproic acid and phenobarbital. As he had frequent convulsive fits, CBZ was added. Thirty-four days later, the patient developed hyperthermia (39.5°C), cervical lymphadenopathy, and generalized cutaneous exfoliated maculae and papulae. Biochemical investigation was characterized by a white cell count of (16.1 × 103/μL, 17% eosinophils) and increased levels of aspartate aminotransferase and alanine aminotransferase (50 and 116 IU/L, respectively). CBZ was discontinued. One month later, all the symptoms were progressively relieved. Six weeks after complete recovery, prick and patch skin tests were performed. They were strongly positive at 48-hour reading. About 2 years later, the patient exhibited an extensive pruritic skin rash, 2 days after AMX intake. Laboratory exams showed eosinophilia (7%) but neither elevated liver enzymes nor renal dysfunction. All these symptoms have disappeared 5 days after AMX withdrawal. Intradermal test to AMX was positive but not to other betalactams. Throughout this clinical observation, we report a CBZ-induced DRESS and describe the possibility of cross reactivity between CBZ and AMX. This cross reactivity was observed despite the lack of chemical similarity between both drugs.

Genetic predisposition of life-threatening antiepileptic-induced skin reactions

IMPORTANCE OF THE FIELD

Recent advances in pharmacogenetic studies have uncovered increasingly more genes that predispose individuals to adverse drug reactions. Aromatic antiepileptic drugs (AEDs) are a frequent cause of severe cutaneous adverse reactions (SCAR). A strong genetic association between HLA-B*1502 and carbamazepine (CBZ)-induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) has been shown in Han Chinese patients.

AREAS COVERED IN THIS REVIEW

This article reviews and updates genetic information associated with CBZ and other AEDs causing SCAR in different ethnic populations.

WHAT THE READER WILL GAIN

Independent studies from different countries confirmed that patients carrying the HLA-B*1502 are at high risk of SJS/TEN when exposed to CBZ. The US FDA and similar regulatory agencies in Canada and Taiwan have updated the CBZ drug label to include the genetic information. Available data also suggest that HLA-B*1502 is a risk allele for SJS/TEN caused by other aromatic AEDs with a similar structure to CBZ.

TAKE HOME MESSAGE

Screening for HLA-B*1502 allele before starting treatment with CBZ is justified in patients from high-risk populations as recommended by regulatory agencies. Similar chemicals should also be avoided in individuals who test positive for HLA-B*1502.

Hyperchloremic metabolic acidosis due to deferasirox in a patient with beta thalassemia major

OBJECTIVE

To report a case of hyperchloremic metabolic acidosis in a patient with beta thalassemia major secondary to treatment with deferasirox due to iron overload.

CASE SUMMARY

A 58-year-old white female with beta thalassemia major was admitted with fever, fatigue, abnormal liver function test results, and hyperchloremic metabolic acidosis (lactate dehydrogenase 494 U/L, aspartate aminotransferase 167 U/L, alanine aminotransferase 250 U/L, gamma-glutamyl transferase 102 U/L, total bilirubin 3.79 mg/dL, direct bilrubin 2.37, potassium 3.3 mEq/L, PO(2) 81.4 mm Hg, PCO(2) 29.4 mm Hg, HCO(3) 16 mEq/L, pH 7.35, chloride 116 mEq/L, anion gap 7.5 mEq/L). Twenty-five days before admission the patient decided to discontinue treatment with deferoxamine for chronic iron overload and continue treatment with oral deferasirox 1500 mg/day. Despite extended clinical and laboratory examination, no obvious cause of fever, hepatitis, or hyperchloremic metabolic acidosis was revealed. Diagnosis was compatible with tubular dysfunction, drug-induced hepatitis, and hypersensitivity reaction due to deferasirox. All pathological findings were fully reversible and our patient had an excellent outcome.

DISCUSSION

The presence of tubular dysfunction should be considered in any patient with otherwise unexplained hyperchloremic metabolic acidosis. In our patient, other potential causes of metabolic hyperchloremic acidosis were ruled out. Toxic effects of deferasirox are probably caused by chelation of mitochondrial iron, leading to adenosine triphosphate depletion in tubular epithelial cells. Use of the Naranjo probability scale revealed that the adverse reaction was probable.

CONCLUSIONS

Kidney toxicity may be a major issue in the management of patients receiving deferasirox. Our case indicates a potential risk of renal toxicity with the presence of tubular dysfunction and hyperchloremic metabolic acidosis in patients undergoing treatment with deferasirox.

Immunogenetics of drug-induced skin blistering disorders. Part I: Perspective

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon the examination of the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events, including Stevens-Johnson syndrome and toxic epidermal necrolysis). An overarching pharmacogenetic schema is proposed. Immune cognition and early-effector processes are focused upon and a challenging synthesis around systems evolution is explained by a variety of projective analogies. Etiology, human leukocyte antigen-B, immune stability, dysregulation, pharmacomimicry, viruses and an aggressive ethnically differentiated 'karmic' response are discussed.

Levetiracetam induced interstitial nephritis and renal failure

A 17-year-old girl who had started on levetiracetam because of new onset partial complex seizures developed acute renal failure and biopsy-confirmed interstitial nephritis 10 days after starting the drug. She made a complete and rapid recovery after discontinuation of levetiracetam and administration of oral corticosteroids. Levetiracetam, known to be predominantly excreted by the kidneys, has not previously been reported to cause significant renal complications in children. Children taking levetiracetam who present with abdominal pain, malaise, vomiting, oliguria, rash, or urticaria may require screening laboratory evaluation for potential renal adverse effects.

Progressive anticonvulsant hypersensitivity syndrome associated with change of drug product

This report describes the laboratory and physical manifestations of lamotrigine-like toxicity in a young man with refractory epilepsy receiving lamotrigine presenting as anticonvulsant hypersensitivity syndrome (AHS) associated with an abrupt change of drug product.

Oral valproic acid for epilepsy--long-term experience in therapy and side effects

Valproic acid (VPA) is considered to be a drug of first choice and one of the most frequently-prescribed antiepileptic drugs worldwide for the therapy of generalized and focal epilepsies, including special epileptic. It is a broad-spectrum antiepileptic drug and is usually well tolerated. Rarely, serious complications may occur in some patients, including hemorrhagic pancreatitis, coagulopathies, bone marrow suppression, VPA-induced hepatotoxicity and encephalopathy, but there is still a lack of knowledge about the incidence and occurrence of these special side effects. Additionally, the consequences for VPA therapy and indication are more or less unclear. By literature review and own data this review addresses some of the challenges of VPA therapy and its side effects, which are not unique to epilepsy in childhood.

Anticonvulsant Hypersensitivity Syndrome: Implications for Pharmaceutical Care

Anticonvulsant hypersensitivity syndrome (AHS) is a delayed adverse drug reaction associated with the use of aromatic anticonvulsant drugs. It has been most commonly reported with the use of phenytoin, carbamazepine, and phenobarbital. Although its occurrence is rare, 1 in every 1000-10,000 exposures, AHS is a serious adverse event often resulting in hospitalization and even death. The clinical manifestations of AHS include a triad of symptoms consisting of dermatologic rashes, fever, and evidence of systemic organ involvement. Diagnosis is most frequently based on the recognition of this triad of symptoms and clinical judgment. The exact mechanism of AHS remains to be determined but is thought to have at least three components: deficiency or abnormality of the epoxide hydroxylase enzyme that detoxifies the metabolites of aromatic amine anticonvulsants, associated reactivation of herpes-type viruses, and ethnic predisposition with certain human leukocyte antigen subtypes. Arene oxides, the toxic intermediaries in the metabolism of anticonvulsant drugs, can accumulate and directly bind to macromolecules, causing cell death, as well as act as prohaptens that bind to T cells, initiating an immune response and systemic reactions. Management of AHS primarily includes discontinuation of the associated anticonvulsant drug. Systemic corticosteroids are usually required for full recovery. An important issue regarding AHS is the cross-sensitivity among aromatic anticonvulsant drugs, which has been reported to be 40-80%. This means that patients with a history of AHS should avoid further use of any aromatic anticonvulsant drug. In addition, a familial association with AHS exists, and family members of the patient with AHS should be educated that they may be at increased risk for developing AHS if they use aromatic anticonvulsant drugs. Anticonvulsant drugs that are generally considered safe are valproic acid and benzodiazepines. Other nonaromatic anticonvulsant drugs should also be acceptable. Pharmacists as health care providers can play an important role in the diagnosis, treatment, and prevention of AHS.

Idiosyncratic adverse reactions to antiepileptic drugs

Idiosyncratic drug reactions may be defined as adverse effects that cannot be explained by the known mechanisms of action of the offending agent, do not occur at any dose in most patients, and develop mostly unpredictably in susceptible individuals only. These reactions are generally thought to account for up to 10% of all adverse drug reactions, but their frequency may be higher depending on the definition adopted. Idiosyncratic reactions are a major source of concern because they encompass most life-threatening effects of antiepileptic drugs (AEDs), as well as many other reactions requiring discontinuation of treatment. Based on the underlying mechanisms, idiosyncratic reactions can be differentiated into (1) immune-mediated hypersensitivity reactions, which may range from benign skin rashes to serious conditions such as drug-related rash with eosinophilia and systemic symptoms; (2) reactions involving unusual nonimmune-mediated individual susceptibility, often related to abnormal production or defective detoxification of reactive cytotoxic metabolites (as in valproate-induced liver toxicity); and (3) off-target pharmacology, whereby a drug interacts directly with a system other than that for which it is intended, an example being some types of AED-induced dyskinesias. Although no AED is free from the potential of inducing idiosyncratic reactions, the magnitude of risk and the most common manifestations vary from one drug to another, a consideration that impacts on treatment choices. Serious consequences of idiosyncratic reactions can be minimized by knowledge of risk factors, avoidance of specific AEDs in subpopulations at risk, cautious dose titration, and careful monitoring of clinical response.

Generation and characterization of antigen-specific CD4+, CD8+, and CD4+CD8+ T-cell clones from patients with carbamazepine hypersensitivity

BACKGROUND

Hypersensitivity is a serious manifestation of anticonvulsant therapy characterized by infiltration of the epidermis and dermis by activated CD8(+) and CD4(+) T-cells, respectively. Attempts to characterize drug-specific CD8(+) T cells have been largely unsuccessful.

OBJECTIVES

The aim of these studies was to generate and characterize CD4(+), CD8(+), and CD4(+)CD8(+) T cells in patients with carbamazepine hypersensitivity.

METHODS

Carbamazepine-specific T-cell clones were generated from 5 patients by using modified cloning methodologies. Cell surface receptor phenotype, functionality, and mechanisms of antigen presentation were then compared.

RESULTS

Ninety CD4(+), 23 CD8(+), and 14 CD4(+)CD8(+) carbamazepine-specific T-cell clones were generated. CD4(+) T-cell clones proliferated vigorously with carbamazepine associated with MHC class II but exhibited little cytotoxic activity. In contrast, most CD8(+) T cells proliferated weakly but effectively killed target cells via an MHC class I or MHC class II restricted, perforin-dependent pathway. CD4(+)CD8(+) T cells displayed characteristics similar to those of CD4(+) T cells; however, drug stimulation was demonstrable in the absence of antigen-presenting cells. Carbamazepine was presented to CD4(+), CD8(+), and CD4(+)CD8(+) T cells in the absence of antigen processing. Drug stimulation resulted in the secretion of IFN-gamma and IL-5. A panel of CD11a(+)CD27(-) clones differentially expressed the receptors CXCR4, CCR4, CCR5, CCR8, CCR9, and CCR10.

CONCLUSION

Carbamazepine-specific CD4(+), CD8(+), and CD4(+)CD8(+) T cells exist in the peripheral circulation of hypersensitive patients, often many years after the resolution of clinical manifestations.

CLINICAL IMPLICATIONS

Carbamazepine-specific CD4(+), CD8(+), and CD4(+)CD8(+) T cells displaying different effector functions and homing characteristics persist in hypersensitive patients' blood for many years after resolution of clinical symptoms.

Oral rapid loading of valproic acid—An alternative to the usual saturation scheme?

Valproic acid (VPA) is considered to be a drug of first choice for the therapy of generalized and focal epilepsies. Due to its broad field of application and its good compatibility, VPA is one of the most frequently prescribed antiepileptic drugs (AED) worldwide. Previous studies have examined the safety and tolerability of rapid intravenous-loaded VPA in the treatment of epilepsy and status epilepticus, but rapid oral loading has not been evaluated in paediatrics systematically in the past. The standard titration scheme takes 10-14 days, some physicians prefer a slower titration of up to 4 weeks. At many institutes, especially children are treated as inpatients until the desired dosage is reached. This causes high costs to the health system and is very inconvenient for the families affected. We have developed a new loading scheme to achieve a therapeutic serum level on the third day of treatment, in order to minimize the time between the beginning of the therapy and reaching the therapeutic serum level. This is the first attempt at doing this with VPA for children with epilepsy.