Allergy to carbamazepine: parallel in vivo and in vitro detection

Genotyping for HLA risk alleles versus patch tests to diagnose anti-seizure medication induced cutaneous adverse drug reactions

Aim: To provide a comparison of genotyping for HLA risk alleles versus patch testing to determine which of these two tests is a better diagnostic tool for cutaneous hypersensitivity reactions caused by anti-seizure medication. Methods: A literature study was performed in PubMed to assess the sensitivity and specificity of HLA genotyping and patch tests for identifying anti-seizure medication induced cutaneous hypersensitivity reactions. Results: This study shows that HLA-B*15:02 genotyping shows high sensitivity for carbamazepine-induced SJS/TEN, especially in Han Chinese and Southeast Asian patients (66.7-100.0%) whereas the sensitivity of patch tests (0.0-62,5%), HLA-A*31:01 (0-50%) and HLA-B*15:11 (18.2-42.9%) are lower. On the contrary, for carbamazepine and phenytoin induced DRESS, patch tests (respectively 70.0-88.9% and 14.3-70.0%) show higher sensitivity than HLA tests (0-66.7% and 0-12.7%). Also for lamotrigine-induced DRESS patch tests perform better than HLA-B*15:02 (33.3-40.0 versus 0%). For anti-seizure medication induced MPE and for oxcarbazepine-induced SCARs more studies are needed. Conclusion: Use of HLA-B genotyping may aid clinicians in the diagnosis of carbamazepine, phenytoin, lamotrigine and oxcarbazepine induced SJS/TEN, particularly in Han Chinese and Southeast Asian patients. On the other hand, patch tests seem to perform better in the diagnosis of carbamazepine and phenytoin induced DRESS.

Delayed hypersensitivity to antiepileptic drugs in children

BACKGROUND

Antiepileptic drugs (AEDs) are widely used for the treatment of epilepsy, but they can be associated with the development of mainly delayed/non-immediate hypersensitivity reactions (HRs). Although these reactions are usually cutaneous, self-limited, and spontaneously resolve within days after drug discontinuation, sometime HR reactions to AEDs can be severe and life-threatening.

AIM

This paper seeks to show examples on practical management of AED HRs in children starting from a review of what it is already known in literature.

RESULTS

Risk factors include age, history of previous AEDs reactions, viral infections, concomitant medications, and genetic factors. The diagnostic workup consists of in vivo (intradermal testing and patch testing) and in vitro tests [serological investigation to exclude the role of viral infection, lymphocyte transformation test (LTT), cytokine detection in ELISpot assays, and granulysin (Grl) in flow cytometry. Treatment is based on a prompt drug discontinuation and mainly on the use of glucocorticoids.

CONCLUSION

Dealing with AED HRs is challenging. The primary goal in the diagnosis and management of HRs to AEDs should be trying to accurately identify the causal trigger and simultaneously identify a safe and effective alternative anticonvulsant. There is therefore an ongoing need to improve our knowledge of HS reactions due to AED medications and in particular to improve our diagnostic capabilities.

Psychiatric medications: adverse cutaneous drug reactions

Psychiatric medications are among the most widely prescribed medications in the United States. Adverse cutaneous drug reactions are associated with psychiatric medications in approximately 2% to 5% of the individuals for whom they are prescribed. Although most adverse cutaneous drug reactions associated with psychotropic medications are benign and easily treated, some can be disfiguring or life-threatening, particularly those associated with the mood stabilizers. Adverse cutaneous drug reactions associated with antidepressants, antipsychotics, and mood stabilizers are reviewed, and important issues that are of concern for the dermatologist who must consider when and how to safely discontinue a psychotropic medication in their patients are presented.

A patch testing and cross-sensitivity study of carbamazepine-induced severe cutaneous adverse drug reactions

BACKGROUND

The usefulness of the drug patch testing for Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) is still controversial. Recent studies have shown that HLA-B*1502 is strongly associated with CBZ-SJS/TEN in Chinese and Southeast Asian populations.

OBJECTIVE

To evaluate the usefulness of patch tests for patients with carbamazepine (CBZ)-induced SJS, TEN and drug reaction with eosinophilia and systemic symptoms (DRESS) and the cross-reactivity in patch tests among the aromatic antiepileptic drugs.

METHODS

We measure the frequency of positive patch test reactions and cross-sensitivity to structure-related aromatic anti-epileptic drugs (AEDs) for patients after SJS/TEN or DRESS episodes caused by CBZ. CBZ and other structure-related AEDs used for patch testing were prepared in 10% and 30% petrolatum. Secondary measures included the association of HLA-B*1502 genotype and frequency of possible side effects from the patch tests.

RESULTS

Positive patch test reactions to 30% CBZ in the CBZ-SJS/TEN were 62.5% (10/16), and 70% (7/10) in the CBZ-DRESS. None of the 10 healthy controls displayed a positive reaction to tested agents. Cross-sensitivity to other aromatic AEDs was observed in both the CBZ-SJS/TEN and the CBZ-DRESS. Only the HLA-B*1502 genotype was present and strongly associated with the CBZ-SJS/TEN, but not with the CBZ-DRESS.

CONCLUSION

Drug patch testing is a safe and useful method for the identification of CBZ as the culprit drug of SJS/TEN as well as DRESS. Testing of chemically or pharmacologically related AEDs may provide information on cross-reactivity for these patients.

Patch testing in non-immediate drug eruptions

The present review addresses the literature regarding the sensitivity and specificity of the various diagnostic methods for evaluating non-immediate (ie, occurring more than 1 hour after drug administration) hypersensitivity reactions associated with β-lactams and other antibiotics, anticonvulsants, heparins, iodinated contrast media, etc. Such reactions include several clinical entities, which range from mild reactions, such as maculopapular rash and delayed-appearing urticaria, to severe ones, such as acute generalized exanthematous pustulosis (AGEP), Stevens-Johnson syndrome, and toxic epidermal necrolysis (TEN). Clinical and laboratory studies indicate that a cell-mediated pathogenic mechanism is often involved in maculopapular rashes. However, this mechanism has also been demonstrated in other non-immediate reactions, such as urticarial and/or angioedematous manifestations, TEN, bullous exanthems, and AGEP. Patch tests, together with delayed-reading intradermal tests, lymphocyte transformation tests, and challenges, are useful tools for evaluating non-immediate drug eruptions. Patch tests can be performed with any form of commercial drugs and are safer than intradermal tests. However, patch tests are less sensitive than intradermal tests, and their sensitivity may vary, depending on the vehicle used.

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.

Oxcarbazepine: current status and clinical applications

Oxcarbazepine (OXC) was introduced in 1990 and is now registered in 54 countries worldwide as monotherapy, as add-on treatment for partial seizures, with or without secondarily generalised seizures, and primary generalised tonic-clonic seizures. OXC and its active metabolite, monohydroxy derivative (MHD), block voltage-dependent sodium channels and may effect potassium and calcium channels. In animal models of epilepsy, OXC and MHD have efficacy similar to that of CBZ. There is no evidence for clinically important teratogenicity, mutagenicity or carcinogenicity. OXC has no effect on serum concentrations of hepatically metabolised anti-epileptic drugs (AEDs) and no clinically important interactions with common non-AEDs, other than hormonal contraceptives. MHD has low protein binding and linear pharmacokinetics. Adverse effects (AEs) are usually related to the central nervous system. Approximately three-quarters of patients who experience adverse effects with CBZ improve when switched to OXC, without loss of seizure control. The incidence of rash appears to be less than that expected with CBZ. While hyponatraemia may occur more often with OXC than with CBZ, it is rarely symptomatic. OXC is an effective and safe drug for the treatment of partial-onset and primary generalised tonic-clonic seizures. Placebo- and low-dose controlled double-blind monotherapy studies prove that OXC has anticonvulsant activity and that therapeutic dosages may be obtained with a 24 h titration in hospitalised patients, if necessary. Comparative double-blind trials show that OXC has similar efficacy to VPA, CBZ and PHT, but has advantages compared to those agents in terms of pharmacokinetics, side-effects and tolerability.

Life-threatening adverse events of antiepileptic drugs

Treating a patient with antiepileptic drugs (AEDs) may give rise to unexpected life-threatening adverse events. Despite extensive experimental and clinical testing to ensure safety, most AEDs on the market have been associated with cases of severe cutaneous reactions, serious hematological disorders, or hepatic failure. Most of these disorders emerge as idiosyncratic immune-mediated disease or are related to toxic metabolic products of the AEDs. Early diagnosis is the only means of reducing the harmful, potentially fatal effects of these reactions. A high degree of suspicion, knowledge of risk factors, and close physician-patient contact increases the likelihood of early diagnosis and treatment. When diagnosed, severe reactions must be fully documented and reported to health authorities. The very rare occurrence of life threatening events should not, in general, limit treatment decision-making. Future epidemiological, chemical, and genetic research might provide methods for ascertaining which patients are at risk, so undue exposure can be avoided.

New drugs for epilepsy

Seizure freedom with no side-effects is the aim of treatment, and new antiepileptic drugs have not lived up to expectations; only a few patients with chronic epilepsy have been rendered seizure-free. These treatments have side-effects but their safety profile may be better than older alternatives, although chronic effects have not yet been established. This article reviews newly marketed antiepileptic drugs. It concentrates on shortcomings of current antiepileptic treatment and on the way drugs are developed. A new approach to treatment is long overdue. The development of rational antiepileptic treatments should be strongly encouraged. More clinically relevant paradigms need to be developed and incorporated into clinical trial programmes as these are presently biased in their designs towards regulatory issues.