Mechanistic perspectives on sulfonamide-induced cutaneous drug reactions

Adverse drug reactions to trimethoprim-sulfamethoxazole in systemic lupus erythematosus

OBJECTIVES

Trimethoprim-sulfamethoxazole (TMP-SMX), a prophylactic agent against pneumocystis pneumonia (PCP), can cause adverse drug reactions (ADRs), particularly in patients with systemic lupus erythematosus (SLE). However, the risk factors for ADRs remain unclear. Thus, we sought to examine the prevalence of TMP-SMX-related ADRs in patients with SLE and identify specific risk factors for ADR development in these patients.

METHODS

We retrospectively reviewed data from patients with connective tissue disease (CTD) who were administered TMP-SMX as a PCP prophylactic. The prevalence of ADRs was compared between patients with SLE and those with other CTDs. Univariate and multivariate analyses were conducted to identify risk factors for ADRs in patients with SLE.

RESULTS

Of the 424 patients with CTD included in our study (SLE, n = 162; other CTDs, n = 262), 22 with SLE (13.6%) developed ADRs, and this rate was significantly higher than that observed in patients with non-SLE CTDs (n = 18 [6.9%], p = 0.033). In patients with SLE, univariate analyses revealed direct associations of ADRs with anti-Sm (p < 0.001), anti-RNP (p = 0.02), and anti-Ro/SS-A antibodies (p = 0.042). Multivariate analysis identified a significant association between anti-Sm antibody levels and the development of ADRs (adjusted odds ratio 5.27, 95% confidence interval 1.80-15.40, p = 0.002).

CONCLUSIONS

Patients with SLE who are prophylactically administered TMP-SMX are at high risk of ADRs. Among these patients, those who display a positive anti-Sm antibody should be carefully monitored for ADRs.

Metal-free regioselective C5-cyanoalkylation of the 8-aminoquinolineamides/sulfonamides via oxidative cross-dehydrogenative coupling with alkylnitriles

A practical, versatile and Metal-free regioselective C5-cyanoalkylation of the 8-aminoquinolineamides/sulfonamides with acetonitrile has been described.

Cutaneous Adverse Effects of Diabetes Mellitus Medications and Medical Devices: A Review

Diabetes mellitus is one of the most prevalent chronic diseases in the USA. If uncontrolled, diabetes can lead to devastating complications. Diabetes medications and medical devices largely contribute to the significant financial expense that the disease inflicts on affected individuals and society. Alongside significant economic burden, there are numerous cutaneous adverse effects associated with diabetes medications and medical devices. Despite the large and increasing number of individuals living with diabetes and the wide use of the related medications and medical devices, there is limited literature that comprehensively documents their cutaneous adverse effects. These cutaneous adverse effects are significant as they can worsen glycemic control, increase disease distress, and may increase risk of associated complications. Thus, it is important that providers can recognize these cutaneous adverse effects, identify the culprit agents, and can properly manage them. In this article, we provide a critical review of the cutaneous adverse effects of medications and devices used in the management of diabetes and provide insight into risk factors and prevention and an overview of therapeutic management. An emphasis is placed on clinical recognition and treatment for use of the medical providers who, regardless of practice setting, will treat patients with diabetes.

Sulfonamide Drug Allergy

PURPOSE OF REVIEW

We sought to review past and current literature on sulfonamide drug allergy and distill it in a practical manner to assist the clinician, specifically focusing on cross-reactivity and desensitization.

RECENT FINDINGS

There do not appear to be consistent genetic markers to reliably predict features of or the presence hypersensitivity reactions. Recent evidence continues to alleviate early concerns cross-reactivity between sulfonamide antibiotics and non-antibiotics. Sulfonamide drug allergy is frequently encountered by the practicing clinician. For sulfonamide antibiotics, delayed rash is the most common clinical manifestation. There is no current evidence to support avoidance of all non-antibiotic sulfonamides in those with a reported allergy to sulfonamide antibiotics, although certain scenarios require caution. Available evidence supports the cautious reintroduction of sulfonamide antibiotics via desensitization, which is usually well tolerated and should be considered in those with strong indications for trimethoprim-sulfamethoxazole and a reported sulfonamide allergy.

Cheminformatics-aided pharmacovigilance: application to Stevens-Johnson Syndrome

Objective Quantitative Structure-Activity Relationship (QSAR) models can predict adverse drug reactions (ADRs), and thus provide early warnings of potential hazards. Timely identification of potential safety concerns could protect patients and aid early diagnosis of ADRs among the exposed. Our objective was to determine whether global spontaneous reporting patterns might allow chemical substructures associated with Stevens-Johnson Syndrome (SJS) to be identified and utilized for ADR prediction by QSAR models.

Materials and Methods Using a reference set of 364 drugs having positive or negative reporting correlations with SJS in the VigiBase global repository of individual case safety reports (Uppsala Monitoring Center, Uppsala, Sweden), chemical descriptors were computed from drug molecular structures. Random Forest and Support Vector Machines methods were used to develop QSAR models, which were validated by external 5-fold cross validation. Models were employed for virtual screening of DrugBank to predict SJS actives and inactives, which were corroborated using knowledge bases like VigiBase, ChemoText, and MicroMedex (Truven Health Analytics Inc, Ann Arbor, Michigan).

Results We developed QSAR models that could accurately predict if drugs were associated with SJS (area under the curve of 75%–81%). Our 10 most active and inactive predictions were substantiated by SJS reports (or lack thereof) in the literature.

Discussion Interpretation of QSAR models in terms of significant chemical descriptors suggested novel SJS structural alerts.

Conclusions We have demonstrated that QSAR models can accurately identify SJS active and inactive drugs. Requiring chemical structures only, QSAR models provide effective computational means to flag potentially harmful drugs for subsequent targeted surveillance and pharmacoepidemiologic investigations.

Zonisamide: newer antiepileptic agent with multiple mechanisms of action

Zonisamide (Zonegran, Eisai, Inc.) is a broad spectrum antiepileptic drug indicated for use as adjunctive therapy in the treatment of partial seizures. Zonisamide has multiple mechanisms of action, which may explain widespread reports of its utility in focal epilepsy and generalized epilepsy, and for nonseizure disorders such as headache and neuropathic pain. Zonisamide has been available in Japan since 1989 and became available in the USA in 2002. The rights to this drug in North America and Europe were recently acquired by Eisai Co. A review of the chemical properties, pharmacokinetics, metabolism, potential mechanisms of action, efficacy in seizure and nonseizure disorders, and tolerability was therefore thought to be timely.

Positivity for anti-RNP antibody is a risk factor for adverse effects caused by trimethoprim-sulfamethoxazole, a prophylactic agent for P. jiroveci pneumonia, in patients with connective tissue diseases

OBJECTIVES

Trimethoprim-sulphamethoxazole (TMP-STX), an agent used for prophylaxis against pneumocystis pneumonia (PCP) in immunocompromised hosts, causes serious adverse effects (AEs) in some patients. The objective of this study was to identify the risk factors for AEs caused by TMP-STX in connective tissue disease (CTD) patients and to describe the clinical features of the AEs.

METHODS

The medical records of 539 patients (CTDs 312, pulmonary diseases 227) receiving TMP-STX for prophylaxis against PCP were reviewed retrospectively. Patients with human immunodeficiency virus were excluded. Univariate and multivariate analyses were conducted to identify the risk factors.

RESULTS

Adverse events caused by TMP-STX occurred in 22 of 312 (7.05 %) CTD patients, while only six of 227 (2.64 %) pulmonary disease patients developed AEs. The incidence of AEs was significantly higher in systemic lupus erythematosus (SLE) (11.0 %) and mixed connective tissue disease (MCTD) (33.3 %) patients than in other CTD patients. AEs occurred in 25 % of patients with anti-RNP antibody. Univariate analysis revealed that SLE, MCTD, and anti-RNP antibody were risk factors for AEs in CTD patients. Further multivariate analyses demonstrated that only anti-RNP antibody positivity was a risk factor for AEs. Systemic inflammation, including fever, was a characteristic manifestation of the AEs in CTD patients, particularly those with anti-RNP antibody.

CONCLUSIONS

Positivity for anti-RNP antibody is a risk factor for AEs caused by TMP-STX in CTD patients. Systemic inflammation, including fever, might be a characteristic feature of the AEs in CTD patients, particularly those with anti-RNP antibody.

Hypersensitivity reactions to HIV therapy

Many drugs used for the treatment of HIV disease (including the associated opportunistic infections) can cause drug hypersensitivity reactions, which vary in severity, clinical manifestations and frequency. These reactions are not only seen with the older compounds, but also with the newer more recently introduced drugs. The pathogenesis is unclear in most cases, but there is increasing evidence to support that many of these are mediated through a combination of immunologic and genetic factors through the major histocompatibility complex (MHC). Genetic predisposition to the occurrence of these allergic reactions has been shown for some of the drugs, notably abacavir hypersensitivity which is strongly associated with the class I MHC allele, HLA-B*5701. Testing before the prescription of abacavir has been shown to be of clinical utility, has resulted in a change in the drug label, is now recommended in clinical guidelines and is practiced in most Western countries. For most other drugs, however, there are no good methods of prevention, and clinical monitoring with appropriate (usually supportive and symptomatic) treatment is required. There is a need to undertake further research in this area to increase our understanding of the mechanisms, which may lead to better preventive strategies through the development of predictive genetic biomarkers or through guiding the design of drugs less likely to cause these types of adverse drug reactions.

Comparison of therapeutic antibiotic treatments on tissue-engineered human skin substitutes

For regenerative medicine to gain clinical acceptance, the effects of commonly used treatment regimens on bioengineered organs must be considered. The antibiotics mafenide acetate (mafenide) and neomycin plus polymyxin (neo/poly) are routinely used to irrigate postoperative skin grafts on contaminated wounds. The effects of these clinically used antibiotics were investigated using tissue-engineered human skin substitutes generated with primary human keratinocytes or the near-diploid human keratinocyte cell line, Near-diploid Immortal Keratinocytes. Following topical or dermal treatment, the skin substitutes were assayed for viability, tissue morphology, glycogen content, and the expression of active caspase 3. Mafenide, but not neo/poly, induced morphological and biochemical changes in tissue-engineered skin substitutes. Keratinocytes in all histological layers of mafenide-treated skin substitutes exhibited ballooning degeneration and glycogen depletion. Mafenide-treatment also triggered separation of basal keratinocytes from the underlying dermis. None of the antibiotic treatments induced apoptosis, as measured by active caspase 3 immunostaining. The results demonstrate that mafenide, but not neo/poly, is detrimental to the viability and structural integrity of tissue-engineered human skin substitutes. These findings highlight the need to identify treatment regimens that are compatible with and hence enable the therapeutic efficacy of first-generation bioengineered organs such as skin.

Zonisamide: review of pharmacology, clinical efficacy, tolerability, and safety

BACKGROUND

Zonisamide (ZNS), a sulphonamide derivative, is a new-generation anticonvulsant with multiple potential mechanisms that contribute to its antiepileptic efficacy and may also explain its as yet incompletely assessed utility for non-seizure disorders such as headaches, neuropathic pain, and weight loss.

OBJECTIVE

A review of the pharmacokinetics, pharmacodynamics, evidence for efficacy in different seizure types and non-seizure conditions, adverse effects, and tolerability of ZNS is presented.

METHODS

A review of all manuscripts published in the English literature on ZNS was performed in preparing this manuscript.

RESULTS/CONCLUSIONS

ZNS has a broad label for use in Japan, while the regulatory bodies in the USA and Europe have approved it for use only as an adjunctive therapy for partial seizures in adults. It has favorable pharmacokinetic characteristics, proven efficacy in seizure disorders, and is well tolerated in long-term use.

Diagnosis and management of HIV drug hypersensitivity

Drug hypersensitivity reactions are an important cause of morbidity in HIV-infected patients who take complex medication regimens. Correct diagnosis and management of these reactions are essential in the clinical care of HIV disease. Trimethoprim-sulfamethoxazole, abacavir, nevirapine, atazanavir, and enfuvirtide can all cause hypersensitivity rashes. In this review, we discuss the evidence for immunologic mechanisms of hypersensitivity reactions to HIV medications, the clinical characteristics of these reactions, and guidelines that currently exist for their identification and management.

Immunopathogenesis of hypersensitivity syndrome reactions to sulfonamides

Cytokines play a role in the immunopathological and molecular mechanisms of sulfonamide-induced hypersensitivity reactions (HSRs). The objective of this study was to analyze the reliability and correlation between the clinical symptoms observed in affected patients (n = 86) because of a sulfonamide-induced HSR and their lymphocyte toxicity assay (LTA) values. Another goal was to determine the cytokine secretion in the patient's sera and their expression in the peripheral blood mononuclear cells (PBMCs) and to explore whether a correlation exists among positive LTA score, cytokine levels, and HSR occurrence. The final goal is to determine whether these measures could be used to predict the likelihood of a patient to experience an HSR during sulfonamide treatment. Such a predictive ability would be valuable to the clinician to know whether the patient would tolerate sulfonamides or whether an alternative antibiotic should be prescribed. The LTA showed a good correlation with the clinical involvement of patients with hypersensitivity syndromes. In addition, the pro-inflammatory cytokines presented significant differences in patients that had rash, fever, and organ involvement than in control patients or any of the other patient groups. Expression of tumor necrosis factor alpha (TNF-alpha) is significantly higher in patients presenting rash, fever, and organ involvement versus all other groups. It is concluded that a positive LTA is a predictor for sulfonamide-induced true HSR. In addition, T-helper cell 1 cytokines [TNF-alpha, interleukins (ILs) 1 and 2] as well as the chemokine regulated upon activation, normal T-cell expressed and secreted (RANTES) control the pathogenesis of sulfonamide-induced HSR and may be used in early diagnosis of the syndrome.

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.

Enzyme-Mediated Protein Haptenation of Dapsone and Sulfamethoxazole in Human Keratinocytes: I. Expression and Role of Cytochromes P450

Cutaneous drug reactions (CDRs) are among the most common adverse drug reactions and are responsible for numerous minor to life-threatening complications. Several arylamine drugs, such as sulfamethoxazole (SMX) and dapsone (DDS), undergo bioactivation, resulting in adduction to cellular proteins. These adducted proteins may initiate the immune response that ultimately results in a CDR. Recent studies have demonstrated that normal human epidermal keratinocytes (NHEKs) can bioactivate these drugs, resulting in protein haptenation. We sought to identify the enzyme(s) responsible for this bioactivation in NHEKs. Using immunofluorescence confocal microscopy and an adduct-specific enzyme-linked immunosorbent assay (ELISA), we found that N-acetylation of the primary amine of SMX and DDS markedly reduced the level of protein haptenation in NHEKs. Detection of mRNA and/or protein confirmed the presence of CYP3A4, CYP3A5, and CYP2E1 in NHEKs. In contrast, although a faint band suggestive of CYP2C9 protein was detected in one NHEK sample, a CYP2C9 message was not detectable. We also examined the ability of chemical inhibitors of cytochromes P450 (aminobenzotriazole and 1-dichloroethylene) and cyclooxygenase (indomethacin) to reduce protein haptenation when NHEKs were incubated with SMX or DDS by either confocal microscopy or ELISA. These inhibitors did not significantly attenuate protein adduction with either SMX or DDS, indicating that cytochromes P450 and cyclooxygenase do not play important roles in the bioactivation of these xenobiotics in NHEKs and thus suggesting the importance of other enzymes in these cells.

Stevens-Johnson syndrome associated with glipizide therapy

We describe a patient with Stevens-Johnson syndrome (erythema multiforme major) associated with an increase in glipizide dosage administration. Glipizide is a second-generation sulfonylurea commonly used to treat patients with noninsulin-dependent diabetes mellitus. Although several reports have documented Stevens-Johnson syndrome caused by first-generation sulfonylureas, our case appears to be the first report of a second-generation sulfonylurea associated with Stevens-Johnson syndrome.

Association of drug-serum protein adducts and anti-drug antibodies in dogs with sulphonamide hypersensitivity: A naturally occurring model of idiosyncratic drug toxicity

BACKGROUND

Sulphonamide antimicrobials, such as sulphamethoxazole (SMX), provide effective infection prophylaxis in immunocompromised patients, but can lead to drug hypersensitivity (HS) reactions. These reactions also occur in dogs, with a similar time course and clinical presentation as seen in humans.

OBJECTIVES

Drug-serum adducts and anti-drug antibodies have been identified in sulphonamide HS humans. The aim of this study was to determine whether similar markers were present in dogs with sulphonamide HS.

METHODS

Thirty-four privately owned sulphonamide HS dogs, 10 sulphonamide-'tolerant' dogs, 18 sulphonamide-naïve dogs, and four dogs experimentally dosed with SMX and the oxidative metabolite SMX-nitroso, were tested for drug-serum adducts by immunoblotting, and anti-drug antibodies by ELISA.

RESULTS

Sulphonamide-serum adducts were found in 10/20 HS dogs tested (50%), but in no tolerant dogs. Anti-sulphonamide IgG antibodies were detected in 17/34 HS dogs (50%), but in only one tolerant dog; antibody absorbance values were significantly higher in HS dogs. There was a significant association between the presence of sulphonamide-serum adducts and anti-sulphonamide antibodies (P = 0.009). Anti-drug antibodies were also found in dogs experimentally dosed with SMX-nitroso followed by SMX, but not in a dog dosed with drug vehicle, followed by SMX.

CONCLUSION

Similar humoral markers are present in dogs and humans with sulphonamide HS, supporting the use of dogs as a naturally occurring model for this syndrome in humans. These data suggest the potential use of drug-serum adducts and anti-drug antibodies as markers for sulphonamide HS. Preliminary data indicate that anti-sulphonamide antibodies may be triggered by the SMX-nitroso metabolite, not by the parent drug, in dogs.

Difference in risks of allergic reaction to sulfonamide drugs based on chemical structure

BACKGROUND

The chemical structure of sulfonamide antibiotics and sulfonamide nonantibiotics can affect the potential for adverse reactions.

OBJECTIVE

To assess whether differences in chemical structure of the various sulfonamide drugs influence the risk of allergic events.

METHODS

A case-control study was conducted among patients with diabetes mellitus (DM) using data from the General Practice Research Database. Cases were defined as patients with a diagnosis of hypersensitivity or allergic reaction. The date of the last event was the index date. Controls were matched on practice, type of DM, and index date. Current use of sulfonamides was defined as use in a 14 day time window before the index date. Sulfonamides were classified according to the presence/absence of an N1 substituent (N1(+)/(-)) and/or an arylamine (N4(+)/(-)). Conditional logistic regression was used to estimate strength of association and expressed as odds ratios and 95% confidence intervals.

RESULTS

Overall, current use of N1(+) N4(+) sulfonamide drugs was associated with the outcome (adjusted OR 3.71; 95% CI 1.40 to 9.81). Current use of N1(+) N4(-) and N1(-) N4(-) sulfonamide drugs was also associated with the occurrence of allergic reactions, although not as strongly: adjusted OR 2.48 (95% CI 2.12 to 2.89) and 2.07 (95% CI 1.74 to 2.46), respectively. Sex and age seemed to be effect modifiers. There was no clear evidence for effect modification by immune disease state.

CONCLUSIONS

Although we did not identify major differences between the groups, we believe that this approach is an innovative manner to examine adverse drug reactions by using chemical structure instead of therapeutic drug classes to classify exposure.

Bioactivation, protein haptenation, and toxicity of sulfamethoxazole and dapsone in normal human dermal fibroblasts

Cutaneous drug reactions (CDRs) associated with sulfonamides are believed to be mediated through the formation of reactive metabolites that result in cellular toxicity and protein haptenation. We evaluated the bioactivation and toxicity of sulfamethoxazole (SMX) and dapsone (DDS) in normal human dermal fibroblasts (NHDF). Incubation of cells with DDS or its metabolite (D-NOH) resulted in protein haptenation readily detected by confocal microscopy and ELISA. While the metabolite of SMX (S-NOH) haptenated intracellular proteins, adducts were not evident in incubations with SMX. Cells expressed abundant N-acetyltransferase-1 (NAT1) mRNA and activity, but little NAT2 mRNA or activity. Neither NAT1 nor NAT2 protein was detected. Incubation of NHDF with S-NOH or D-NOH increased reactive oxygen species formation and reduced glutathione content. NHDF were less susceptible to the cytotoxic effect of S-NOH and D-NOH than are keratinocytes. Our studies provide the novel observation that NHDF are able to acetylate both arylamine compounds and bioactivate the sulfone DDS, giving rise to haptenated proteins. The reactive metabolites of SMX and DDS also provoke oxidative stress in these cells in a time- and concentration-dependent fashion. Further work is needed to determine the role of the observed toxicity in mediating CDRs observed with these agents.

Reactive oxygen species generation and its role in the differential cytotoxicity of the arylhydroxylamine metabolites of sulfamethoxazole and dapsone in normal human epidermal keratinocytes

Cutaneous drug reactions (CDR) are responsible for numerous minor to life-threatening complications. Though the exact mechanism for CDR is not completely understood, evidence suggests that bioactivation of drugs to reactive oxygen or nitrogen species is an important factor in the initiation of these reactions. Several CDR-inducing drugs having an arylamine functional group, such as sulfamethoxazole (SMX) and dapsone (DDS), undergo bioactivation to reactive arylhydroxylamine metabolites. These metabolites can generate cellular oxidative stress by forming reactive oxygen species (ROS). Several studies have demonstrated a higher cytotoxicity with DDS hydroxylamine (DDS-NOH) compared to SMX hydroxylamine (SMX-NOH). To investigate the role of differential ROS generation in the higher cytotoxicity of DDS-NOH, hydroxylamine metabolites of SMX and DDS were synthesized and ROS formation by these metabolites determined. DDS-NOH and its analogues/metabolites consistently resulted in higher ROS formation as compared to SMX-NOH. However, comparison of the ROS generation and cytotoxicity of a series of arylhydroxylamine analogues of DDS did not support a simple correlation between ROS generation and cell death. Numerous ROS scavengers were found to reduce metabolite-induced ROS formation, with differences in the potency between the agents. The decrease in DDS-NOH-induced ROS generation in NHEK with ascorbic acid, N-acetylcysteine, Trolox, and melatonin was 87, 86, 44, and 16%, respectively. Similarly, the cytotoxicity and adduct formation of DDS-NOH in NHEK was reduced in the presence of ascorbic acid. In summary, these studies show that arylhydroxylamine metabolites of SMX/DDS induce ROS generation in NHEK, though such generation is not directly related to cytotoxicity.

Drug bioactivation, covalent binding to target proteins and toxicity relevance

A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.

Sulfonamide Cross-Reactivity: Fact or Fiction?

OBJECTIVE:

To provide a critical and comprehensive review of the literature, specifically case reports and observational studies used to support the concept of cross-reactivity between sulfonylarylamines and non-sulfonylarylamines.

DATA SOURCES:

A list of medications was formulated from several different review articles. A MEDLINE/PubMed search was conducted (1966–March 2004) using the individual medications and the MeSH terms of drug hypersensitivity/etiology, sulfonamides/adverse effects, and/or cross-reaction.

STUDY SELECTION AND DATA EXTRACTION:

A critical review of the methodology and conclusions for each article found in the search was conducted. The manufacturer's package insert (MPI) for each drug was examined for a statement concerning possible cross-reactivity in patients with a sulfonamide allergy. If indicated, the manufacturers were contacted to obtain any clinical data supporting the statement.

DATA SYNTHESIS:

A total of 33 medications were identified. Seventeen (51.5%) of the MPIs contained statements of varying degrees concerning use in patients with a “sulfonamide” allergy; 21 case series, case reports, and other articles were found.

CONCLUSIONS:

After a thorough critique of the literature, it appears that the dogma of sulfonylarylamine cross-reactivity with non-sulfonylarylamines is not supported by the data. While many of the case reports on the surface support the concept of cross-reactivity, on closer examination the level of evidence in many of the cases does not conclusively support either a connection or an association between the observed cause and effect.

Safety of the new selective cyclooxygenase type 2 inhibitors rofecoxib and celecoxib in patients with anaphylactoid reactions to nonsteroidal anti-inflammatory drugs

BACKGROUND

Controlled oral challenge with nonsteroidal anti-inflammatory drugs (NSAIDs) is the only definite way to detect safe NSAIDs in patients with NSAID-induced anaphylactoid reactions.

OBJECTIVE

To evaluate the safety of the selective cyclooxygenase (COX) type 2 inhibitors rofecoxib and celecoxib in patients with single-reactive, NSAID-induced anaphylactoid reactions.

METHODS

We prospectively conducted single-blind, placebo-controlled oral challenges (SBPCOCs) with rofecoxib and celecoxib in 33 patients with single-reactive, NSAID-induced anaphylactoid reactions.

RESULTS

Nineteen women and 14 men (age range, 20-78 years; mean age, 44.8 years) exhibited anaphylactoid reactions on emergency department admission. Symptoms involved the skin (100%), laryngeal edema (73%), systolic hypotension (39%), and the gastrointestinal system (15%). The NSAIDs most frequently involved in the episodes were dipyrone (64%), propyphenazone (12%), and diclofenac (12%). In all patients, tolerance to a potent, nondiscriminatory COX inhibitor (except those reported as being responsible for the reaction) was noted. The SBPCOCs with the selective COX-2 inhibitors celecoxib and rofecoxib were well tolerated in all cases. Twenty-three patients who had an anaphylactoid reaction involving dipyrone and propyphenazone showed good tolerance to celecoxib (which contains a pyrazole group in its structure) on challenge.

CONCLUSIONS

The SBPCOCs with highly selective COX-2 inhibitors were safe in patients with single-reactive, NSAID-induced anaphylactoid reactions, even in cases that involved pyrazole derivatives.

The danger hypothesis applied to idiosyncratic drug reactions

PURPOSE OF REVIEW

Idiosyncratic drug reactions pose a significant clinical threat and hamper drug development. The idiosyncratic nature of these reactions has made mechanistic studies exceedingly difficult, and yet without a better understanding of the mechanisms involved it is unlikely that much progress can be made in dealing with the problem. Several working hypotheses have been used to study these reactions, but none fits all of the characteristics that are observed. Borrowed from immunology, the danger hypothesis has most recently been used to explain several characteristics of these reactions. The present review describes the danger hypothesis and compares it with previous hypotheses to determine how well each fits with the observed characteristics of the reactions.

RECENT FINDINGS

Slow progress in the field continues and it is important to use new observations, such as identifying T cells that recognize drugs in the absence of reactive metabolite formation, to test and refine the working hypotheses. However, the development of animal models of idiosyncratic drug reactions as well as progress in basic immunology and genomics are likely to accelerate progress in this area in the near future.

SUMMARY

No one model fits the characteristics of all idiosyncratic drug reactions; however, the danger model provides a new perspective and suggests avenues of research that have the potential to increase our ability to predict and prevent such reactions significantly.