Anticonvulsant hypersensitivity syndrome

Establishing causality in pediatric adverse drug reactions: use of the Naranjo probability scale

Carbamazepine hypersensitivity syndrome is a rare, life-threatening condition. Its diagnosis is critical to avoid future exposure to aromatic anticonvulsants. Pediatricians rarely use a systematic approach to establish the cause of drug reactions in the clinical setting. We describe the use of the Naranjo adverse drug reaction probability scale to establish causality in three cases of suspected anticonvulsant hypersensitivity syndrome with the aim of introducing clinicians to this effective tool. Our analysis reveals that this method is useful, but also highlights potential areas for its improvement.

Chemical toxicology: reactive intermediates and their role in pharmacology and toxicology

Reactive intermediates formed during the metabolism of drugs have been investigated extensively over the past decades. Today, interest in reactive intermediates in drug discovery is focused on minimising bioactivation in hopes of reducing the risk of causing so-called idiosyncratic toxicity. These efforts are justified based on the 'hapten hypothesis', namely, that on binding to protein, reactive intermediates may elicit an immune response to the modified protein, leading to a cascade of events that ultimately manifests as a toxic outcome. However, the pharmacological action of certain drugs depends on reactive intermediates that modify critical amino acid residues of proteins, typically enzymes, thereby altering their activity. Thus, the notion that reactive intermediates are inherently dangerous is unjustified. When a reactive intermediate is necessary for the desired pharmacological effect of a drug, the selectivity it displays towards the target protein is crucial, as off-target binding may produce unwanted toxicities. On the other hand, reactive intermediates may play no role in toxicity. This review provides a balanced perspective, primarily focusing on the proposed role of reactive intermediates in drug toxicity, while also highlighting examples in which they are involved in causing the desired pharmacology. It is hoped that this knowledge can help scientists involved in drug discovery and development in their challenging task of producing safe and effective drugs.

Cross-sensitivity in a child with anticonvulsant hypersensitivity syndrome

We describe a fulminant picture of anticonvulsant hypersensitivity syndrome (AHS) and the possible role of nitrazepam. A 5-month-old boy developed fever and rash after the use of phenobarbitone. Allergy to phenobarbitone was suspected. Nitrazepam was substituted for seizure control. Over the next few days he progressively collapsed with fever, facial oedema and multi-organ involvement. The diagnosis of AHS was delayed because nitrazepam has not been implicated in the development of cross-sensitivity. AHS is a severe multi-organ reaction to aromatic anti-epileptic drugs. It has been thought to occur as a consequence of pre-existing pharmacogenetic and immunologic abnormalities. Careful selection of anti-epileptic drugs is essential as cross-sensitivity is common. Intermittent benzodiazepines have been recommended in managing breakthrough seizures in AHS. However, the structure of benzodiazepines contains aromatic rings and potential cross-reactivity cannot be totally ignored. Although we do not have direct proof, we believe that nitrazepam prolonged the clinical course.

Life-threatening acute adverse cutaneous drug reactions

Adverse cutaneous reactions to drugs are frequent, affecting 2% to 3% of all hospitalized patients. Fortunately, only about 2% of adverse cutaneous reactions are severe and very few are fatal. Stevens-Johnson syndrome and toxic epidermal necrolysis are severe life-threatening diseases with a mortality rate reaching 30%, and only prompt recognition and diagnosis, withdrawal of the offensive drug, and referral to an intensive care unit or burn care unit might improve the prognosis and save the patient's life. Drug eruption with eosinophilia and systemic symptoms syndrome, formerly termed drug hypersensitivity syndrome, is a rather distinct severe adverse drug reaction (ADR) characterized by eruption, fever, lymph node enlargement, and single or multiple organ involvement, with a high morbidity and a mortality rate of 10%. These severe ADRs, together with serum sickness-like syndrome, are discussed in this review. Other severe reactions, such as anaphylaxis and vasculitis, are discussed elsewhere in this issue. Although most of the readers, particularly those in the outpatient arena, will not be treating these patients, they are the ones who will see them first, diagnose them, realize the potential danger in their condition, and refer them to the appropriate treatment venue. Therefore, dermatologists should be familiar with these conditions and be prepared to handle them adequately.

Anticonvulsant hypersensitivity syndrome: a review

Anticonvulsant hypersensitivity syndrome (AHS), characterised by fever, rash and internal organ involvement, is a rare, but potentially fatal adverse event that occurs most commonly with first-line aromatic anticonvulsants, but can also occur with non-aromatic anticonvulsants such as lamotrigine and valproic acid. AHS can begin anywhere from 1 to 12 weeks after commencement of therapy and has been estimated to occur at a frequency of 1/1000 to 1/10,000 exposures. Its true incidence, however, remains unknown due to under-reporting. The disease has protean manifestations mimicking several other conditions, and the diagnosis is thus difficult. Several hypotheses have been put forward to explain the pathogenesis of AHS. These include accumulation of toxic metabolites, graft versus host disease, antibody production and viral infections. The one based on toxic metabolites has found the greatest acceptance, perhaps due to the fact that it can be proven by an in vitro test; the lymphocyte toxicity assay. Discontinuation of the offending agent with supportive, symptomatic therapy forms the mainstay of management of AHS. In addition, counselling of both the patient and first degree relatives for susceptibility to AHS is an important aspect of management. In the last decade, several new anticonvulsants have been introduced for epilepsy. In addition, for resource-poor countries, inexpensive and effective first-line drugs such as phenytoin and phenobarbitone will continue to remain important treatment options. Thus, the problem of AHS will continue, and attempts should be made to further understand the molecular basis of and individual susceptibility to AHS. Adverse event monitoring programs must also actively seek AHS reports to estimate its true incidence.

Anticonvulsant Hypersensitivity Syndrome: Lymphocyte Toxicity Assay for the Confirmation of Diagnosis and Risk Assessment

OBJECTIVE

To report a case of anticonvulsant hypersensitivity syndrome (AHS) precipitated by exposure to phenobarbital.

Case Summary

An 11-year-old girl receiving phenobarbital developed fever, exfoliative skin rash, mucous membrane lesions, alopecia, and hepatic inflammation. Investigations ruled out an infectious etiology; an adverse event following phenobarbital administration was considered. Applying the Naranjo probability scale for objective causality assessment showed the adverse reaction was probably due to phenobarbital. The diagnosis was confirmed by in vitro lymphocyte toxicity assay, which demonstrated increased cell death following exposure to phenobarbital, as well as other aromatic anticonvulsants and lamotrigine.

DISCUSSION

AHS is a rare, potentially fatal event with multisystem manifestations. It is reported following exposure to aromatic antiepileptics. The mechanism proposed for AHS is accumulation of toxic arene oxide metabolites due to a defect in epoxide hydrolase—mediated detoxification. Despite the difference in chemical structure of lamotrigine, in vitro susceptibility to AHS was demonstrated in our patient.

CONCLUSIONS

Although AHS is a rare event, it should be suspected in patients who develop unexplained systemic manifestations following exposure to aromatic antiepileptics. The potential of lamotrigine to cause AHS should be remembered when this drug is used in subjects who have developed AHS on exposure to phenobarbital and other first-line antiepileptic agents.

Adverse cutaneous reactions to mood stabilizers

Of all the psychotropic medications currently available, the mood-stabilizing agents have the highest incidence of severe and life-threatening adverse cutaneous drug reactions (ACDRs). An exanthematous eruption in a patient treated with a mood-stabilizing agent should be viewed as possibly being the initial symptom of a severe and life-threatening ACDR, such as a hypersensitivity reaction, Stevens-Johnson syndrome, or toxic epidermal necrolysis. The combination of mood-stabilizing agents may increase the risk of such reactions. The mood-stabilizing agents addressed in this article are carbamazepine, lithium carbonate, valproic acid, topiramate, lamotrigine, gabapentin, and oxcarbazepine. Prior to the initiation of a mood stabilizer, the potential benefits, risks, and adverse effects should be communicated to the patient. If possible, slow dose escalation should be attempted by the physician. Patients should also be advised to seek medical attention if they suspect a drug-induced skin reaction. If the physician suspects a severe ACDR, the offending agent should be removed immediately.

Antiepileptic hypersensitivity syndrome: clinicians beware and be aware

Antiepileptic hypersensitivity syndrome is a serious idiosyncratic, non-dose-related adverse reaction reported to occur with phenytoin, phenobarbital, carbamazepine, primidone, and lamotrigine. The reaction usually develops 1 to 12 weeks after initiation of therapy with one of the above agents and is recognized by the classic triad of fever, rash, and internal organ involvement. Immediate discontinuation of the suspected anticonvulsant is essential for good outcome. Patients usually are managed supportively with hydration, antihistamines, H(2)-receptor blockers, and topical corticosteroids. In severe cases, the use of systemic corticosteroids may be necessary. The use of intravenous immune globulin should be limited to severe cases where Kawasaki disease or idiopathic thrombocytopenic purpura cannot be ruled out. Education of health care professionals and patients is imperative to improving outcomes and prevention of this reaction in the future.

Arthritis as a rare side effect of phenytoin therapy

Anticonvulsant hypersensitivity syndrome is an uncommon side effect of phenytoin. It is characterized by fever, skin reactions, lymphadenopathy, and severe multiorgan involvement. Atypical clinical features have rarely been described. We observed a unique case of anticonvulsant hypersensitivity syndrome in a 77-year-old woman in whom fever and monoarthritis were the main clinical features. Symptoms dramatically subsided after phenytoin withdrawal.

Drug-induced hypersensitivity syndrome in pediatric patients

The antiepileptic hypersensitivity syndrome is a severe, multiorgan reaction to oral antiepileptics that manifests as fever, rash, lymphadenopathy, and hepatitis. This same reaction pattern also has been described following administration of a few unrelated medications. We report on 11 patients who had drug-induced hypersensitivity syndrome and were admitted to our pediatric service and review 94 cases of this syndrome in pediatric patients identified from the literature. We undertook this study to summarize the findings and alert clinicians to the severe internal organ involvement that can occur with this syndrome.

Possible atypical cross-sensitivity between phenytoin and carbamazepine in the anticonvulsant hypersensitivity syndrome

Anticonvulsant hypersensitivity syndrome (AHS) is a rare but potentially life-threatening reaction that occurs in response to common anticonvulsants in predisposed individuals. It is often characterized by fever, rash, lymphadenopathy, hepatitis, and laboratory abnormalities. Consequently, it often is overlooked or even misdiagnosed by practitioners unfamiliar with AHS. Cross-sensitivity manifests frequently between phenytoin, phenobarbital, and carbamazepine as an exacerbation of presenting signs and symptoms. We report a case of AHS in a patient whose clinical features changed significantly when switching from phenytoin to carbamazepine. Physicians and pharmacists must become aware of the extreme variability in AHS manifestation so that the offending anticonvulsant regimen can be discontinued in a timely manner.

A case report of olanzapine-induced hypersensitivity syndrome

Hypersensitivity syndrome is defined as a drug-induced complex of symptoms consisting of fever, rash, and internal organ involvement. The hypersensitivity syndrome is well recognized as being caused by anticonvulsants. Olanzapine is an atypical antipsychotic agent whose side effects include sedation, weight gain, and increased creatinine kinase and transaminase levels. To date, there have been no reports of hypersensitivity syndrome related to this drug. A 34-year-old man developed a severe generalized pruritic skin eruption, fever, eosinophilia, and toxic hepatitis 60 days after ingestion of olanzapine. After termination of olanzapine treatment, the fever resolved, the skin rash was reduced, eosinophil count was reduced to normal, and the transaminase levels were markedly reduced. Clinical features and the results of skin and liver biopsies indicated that the patient developed hypersensitivity syndrome caused by olanzapine.

Lamotrigine overdose presenting as anticonvulsant hypersensitivity syndrome

OBJECTIVE

To describe the laboratory and physical manifestations of lamotrigine toxicity presenting as anticonvulsant hypersensitivity syndrome.

CASE SUMMARY

A 49-year-old white man presented to our institution with a two-day history of low-grade fever, erythema, and edema involving the periorbital area. Five days earlier, he had been placed on lamotrigine treatment for bipolar disorder. He inadvertently received four daily doses of lamotrigine 2700 mg each. Physical examination was significant for periorbital edema and discrete and confluent blanching red macules and papules involving the face, trunk, and extremities. Laboratory tests revealed leukocytosis, hepatitis, and acute renal failure. With normalization of the laboratory results, the eruptions and edema gradually resolved.

DISCUSSION

Lamotrigine toxicity can lead to periorbital edema, rash, and multiorgan system abnormalities. This presentation has clinical and laboratory similarities with anticonvulsant hypersensitivity syndrome, which suggests that at some threshold concentration the amount of lamotrigine may overwhelm the body's ability to metabolize the drug, leading to a similar hypersensitivity reaction. Lamotrigine is a relatively new agent, and this report may provide useful insights on evaluating the clinical toxicology of this agent.

CONCLUSIONS

Healthcare providers should be aware that lamotrigine overdose may present with multiorgan involvement, similar to anticonvulsant hypersensitivity syndrome.

Anticonvulsant hypersensitivity syndrome occurring as sepsis with multiorgan dysfunction

Phenytoin is a highly effective and widely prescribed anticonvulsant agent. However, it is associated with both dose-related side effects and hypersensitivity reactions. Life-threatening anticonvulsant hypersensitivity syndrome in one patient was characterized by a skin eruption and multisystem organ dysfunction.