Mechanisms of drug-induced allergy

Shrimp hemocyanin elicits a potent humoral response in mammals and is favorable to hapten conjugation

Conjugation to a carrier protein is essential to give rise to the antigenicity of hapten. Three carrier proteins e.g. KLH (Keyhole Limpet hemocyanin), BSA (bovine serum albumin), and OVA (Ovalbumin) were used mostly. KLH is advantageous to the others, majorly owing to its strong immunogenicity and limited usage in other biological assays. However, the cost of obtaining Keyhole Limpet is high and the solubility of KLH is not as well as the other carriers, especially after hapten conjugation. Here, we extracted the shrimp hemocyanin (SHC) from Litopenaeus vannamei (L. vannamei), which is a commonly sea product worldwide. The high pure SHC could be acquired by two-step purification, with a production yield of > 1 g proteins (98% pure) per 1 kg shrimp. Compared to KLH, the peptide-SHC conjugates exhibit higher solubility after hapten conjugation. Meanwhile, compared with KLH, SHC induces comparable antibody production efficiency in mammals, with or without conjugation. Furthermore, rabbit polyclonal antibodies or mouse monoclonal antibodies were generated by immunizing SHC-peptide conjugates, and the subsequent antibodies were confirmed to be used in western blot, immunofluorescence and immunohistochemistry. Therefore, we demonstrated that SHC may be used as a substitute for KLH in future antibody and vaccine development.

Drug-induced interstitial lung disease: a narrative review of a clinical conundrum

INTRODUCTION

Drug-induced interstitial lung disease (DI-ILD) is increasing in incidence, due to the use of many new drugs across a broad range of cancers and chronic inflammatory diseases. The presentation and onset of DI-ILD are variable even for the same drug across different individuals. Clinical suspicion is essential for identifying these conditions, with timely drug cessation an important determinant of outcomes.

AREAS COVERED

This review provides a comprehensive and up-to-date summary of epidemiology, risk factors, pathogenesis, diagnosis, treatment, and prognosis of DI-ILD. Relevant research articles from PubMed and Medline searches up to September 2023 were screened and summarized. Specific drugs including immune checkpoint inhibitors, CAR-T cell therapy, methotrexate, and amiodarone are discussed in detail. The potential role of pharmacogenomic profiling for lung toxicity risk is considered.

EXPERT OPINION

DI-ILD is likely to be an increasingly important contributor to respiratory disability in the community. These conditions can negatively impact quality of life and patient longevity, due to associated respiratory compromise as well as cessation of evidence-based therapy for the underlying disease. This clinical conundrum is relevant to all areas of medicine, necessitating increased understanding and greater vigilance for drug-related lung toxicity.

Etoposide hypersensitivity reactions associated with in-line filter use: A retrospective cohort study at CHU de Québec-Université Laval

INTRODUCTION

A case series of hypersensitivity reactions (HSRs) during intravenous administration of etoposide was observed following the introduction of in-line filters (ILFs) at a specialized university-affiliated center. This raised questions about the possible involvement of filters in these reactions. Despite there being very little published evidence to inform clinical decision making in this potentially clinically significant situation, the use of ILFs was discontinued at this center pending further investigation. The aims of this study were to evaluate the cumulative incidence of etoposide-related HSR with and without the use of ILF and to describe the reactions in adult and pediatric patients with cancer.

METHODS

A retrospective cohort study was performed among all pediatric and adult patients treated with intravenous etoposide at a maximal concentration of 0.4 mg/mL at our center between 30 September 2015 and 16 August 2018. This covered periods of time during which ILFs were used, as well as 6 months before their implementation and after their withdrawal. Data were extracted from medical records and cumulative incidence was calculated for each of the time periods (pre-ILF, ILF, and post-ILF) as the proportion of patients who recorded an HSR (one or more). Confidence intervals were calculated for each proportion using Fisher's Exact 95%. Comparisons of proportions between time periods were performed using Exact Pearson Chi-squared tests. Data were stratified by a number of perfusion cycles (single cycle or multiple cycles) and by patient population (adult and pediatric).

RESULTS

A total of 284 patients were included in the study. The overall cumulative incidence of etoposide HSR was 9.9%. The cumulative incidence of HSR tended to be higher during ILF use when compared with combined pre- and post-ILF periods (12.2% [95% CI: 7.9-17.8] vs. 5.2% [95% CI: 1.7-11.7], p  =  0.09). In patients who received multiple cycles of etoposide, the cumulative incidence of HSRs was higher during ILF use when compared with combined pre- and post-ILF periods (15.0% [95% CI: 9.6-21.8] vs. 3.9% [95% CI: 0.8-11.0], p  =  0.01). The majority of HSRs' maximal severity were grade 1 or 2 (85.7%) according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.0.

CONCLUSIONS

This study suggests a link between the use of ILFs and increased incidence of HSR during etoposide perfusion.

Clinical Application of In Vitro Tests for COVID-19 Vaccine Delayed Hypersensitivity Diagnostics

Drug hypersensitivity reactions can be classified as immediate or delayed. While diagnostic options for immediate reactions are well developed and standardized, delayed reactions (in many cases type IV according to Gell and Coombs) are a challenge for allergy work-up. In recent years, some in vitro markers have been proposed and used for delayed reactions, such as contact dermatitis. Primary strategy: Avoidance is difficult to achieve, especially for COVID-19 vaccinations, when immunity against infection is extremely important. The aim of our study was to evaluate the application of in vitro delayed hypersensitivity tests in COVID-19 vaccines. Seven patients with a positive history of severe delayed drug allergy were enrolled. Vein blood was collected to stimulate cells with the tested vaccines (Comirnaty, Janssen, Spikevax) and excipients with the assessment of CD40L, CD69, IL-2, IL-4, IL-6, IL-10, IFNgamma, TNFalfa, and intracellular markers: granulysin and INFgamma. In addition, basophile activation tests, patch tests, skin prick tests, and intradermal tests were performed with the tested vaccine. Finally, the decision was made to either administer a vaccine or resign. Two out of seven patients were considered positive for drug hypersensitivity in the in vitro test according to the high vaccine stimulation index measured with CD69 (6.91 and 12.18) and CD40L (5.38 and 15.91). All patch tests, BATs, and skin tests were negative. Serum interleukin measurements were inconclusive as the impact of the vaccine itself on the immunity system was high. Intracellular markers gave uncertain results due to the lack of stimulation on the positive control. CD69 and CD40L could be reliable in vitro markers for delayed hypersensitivity to COVID-19 vaccines. Patch tests, skin tests, BATs, and serum interleukins did not confirm their usefulness in our study.

Dietary parameters in patients with drug allergy: Assessing dietary inflammatory index

Background

Research on the increasing incidence of allergic diseases evidenced the role of diet as a potential key factor. Diet can modulate the low-grade systemic inflammation related to obesity and several diseases. There are no published data on drug allergy.

Aim

To investigate a potential association between diet, including dietary inflammatory index (DII), and drug allergy. Also, to evaluate correlations between diet and obesity, inflammatory and metabolic parameters in patients with drug allergy.

Methods

Ninety consecutive patients studied for suspected drug allergy were evaluated in terms of dietary parameters, anthropometric measurements, bioimpedance and biochemical analysis. DII was calculated based on information collected from a food frequency questionnaire.

Results

After diagnostic work-up, 39 patients had confirmed drug allergy and 45 excluded, representing the study group and the control group, respectively. The majority (79%) were female, with mean age of 39.58±13.3 years. The 84 subjects revealed an anti-inflammatory diet pattern. No significative difference was found in DII scores between drug allergic patients and controls (-3.37±0.95 vs -3.39±0.86, p = 0.985). However, the patients with drug allergy revealed higher obesity and inflammatory parameters. A significative negative correlation was found between DII and adiponectin levels, in the control group (r = -0.311, p = 0.040). In the patient group, a significative positive correlation was observed between DII and triglycerides (r = 0.359, p = 0.032). No other correlations were found between DII and the assessed parameters. Patients with drug allergy presented a significative higher intake of mono-unsaturated fatty-acids comparing to controls (19.8±3.7 vs 17.8 ± 4.0, p = 0.021). No other statistically significant differences were achieved in dietary parameters, between patients and controls.

Conclusion

The population assessed in this study revealed an anti-inflammatory diet profile. Although we have found in a previous work that the same patients with drug allergy revealed higher obesity and inflammatory parameters, the DII did not allow to distinguish between patients with drug allergy or controls. The DII scores correlated with triglycerides levels in the drug allergy patients and inversely with adiponectin levels in the control group. Larger studies are needed to clarify the potential role of the diet in drug allergy and its outcomes.

HLA pharmacogenetic markers of drug hypersensitivity from the perspective of the populations of the Greater Middle East

Specific HLA associations with drug hypersensitivity may vary between geographic regions and ethnic groups. There are little to no data related to HLA-drug hypersensitivity on populations who reside in the Greater Middle East (GME), a vast region spanning from Morocco in the west to Pakistan in the east. In this review, the authors intended to summarize the significant HLA alleles associated with hypersensitive drug reactions induced by different drugs, as have been found in different populations, and to summarize the prevalence of these alleles in the specific and diverse populations of the GME. For example, HLA-B*57:01 allele prevalence, associated with abacavir-induced hypersensitivity, ranges from 1% to 3%, and HLA-DPB1*03:01 prevalence, associated with aspirin-induced asthma, ranges from 10% to 14% in the GME population. Studying pharmacogenomic associations in the ethnic groups of the GME may allow the discovery of new associations, confirm ones found with a low evidence rate and enable cost-effectiveness analysis of allele screening before drug use.

Rare Heterogeneous Adverse Events Associated with mRNA-Based COVID-19 Vaccines: A Systematic Review

Background: Since the successful development, approval, and administration of vaccines against SARS-CoV-2, the causative agent of COVID-19, there have been reports in the published literature, passive surveillance systems, and other pharmacovigilance platforms of a broad spectrum of adverse events following COVID-19 vaccination. A comprehensive review of the more serious adverse events associated with the Pfizer-BioNTech and Moderna mRNA vaccines is warranted, given the massive number of vaccine doses administered worldwide and the novel mechanism of action of these mRNA vaccines in the healthcare industry. Methods: A systematic review of the literature was conducted to identify relevant studies that have reported mRNA COVID-19 vaccine-related adverse events. Results: Serious and severe adverse events following mRNA COVID-19 vaccinations are rare. While a definitive causal relationship was not established in most cases, important adverse events associated with post-vaccination included rare and non-fatal myocarditis and pericarditis in younger vaccine recipients, thrombocytopenia, neurological effects such as seizures and orofacial events, skin reactions, and allergic hypersensitivities. Conclusions: As a relatively new set of vaccines already administered to billions of people, COVID-19 mRNA-based vaccines are generally safe and efficacious. Further studies on long-term adverse events and other unpredictable reactions in close proximity to mRNA vaccination are required.

Bipolar Patients and Bullous Pemphigoid after Risperidone Long-Acting Injectable: A Case Report and a Review of the Literature

Neuropsychiatric disorders are found to be associated with bullous pemphigoid (BP), an autoimmune subepidermal blistering disease. Antipsychotics have emerged as possible inducing factors of BP. However, large sample studies concerning BP associated with antipsychotics, as well as with specific mental disorders, are still lacking. Our review retrieved a few clinical studies and case reports on the topic, producing controversial results. We report for the first time a bipolar patient case presenting BP following five-month therapy with risperidone long-acting injectable (LAI). We hypothesize that the dermatological event is associated with the medication administered. The issue emerged during psychiatric consultation and was confirmed by histological examination, direct and indirect immunofluorescence studies, plus positive plasma and cutaneous BP180 and BP230 IgG. Neurodegeneration or neuroinflammation might represent a primary process leading to a cross-reactive immune response between neural and cutaneous antigens and contributing to self-tolerance failure. Furthermore, the time sequence of the shared biological mechanisms leading to clinical manifestations of the neuropsychiatric disorder and BP remains undefined. BP comorbid with bipolar disorder might occasionally represent a serious health risk and affect patients' physical and psychosocial quality of life. Thus, clinicians treating psychiatric patients should consider BP as a possible adverse effect of psychotropic medications.

Anaphylactic and nonanaphylactic reactions to SARS-CoV-2 vaccines: a systematic review and meta-analysis

BACKGROUND

Currently there is no systematic review and meta-analysis of the global incidence rates of anaphylactic and nonanaphylactic reactions to SARS-CoV-2 vaccines in the general adult population.

OBJECTIVES

To estimate the incidence rates of anaphylactic and nonanaphylactic reactions after COVID-19 vaccines and describe the demographic and clinical characteristics, triggers, presenting signs and symptoms, treatment and clinical course of confirmed cases.

DESIGN

A systematic review and meta-analysis. Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA] statement was followed.

METHODS

Electronic databases (Proquest, Medline, Embase, Pubmed, CINAHL, Wiley online library, and Nature) were searched from 1 December 2020 to 31 May 2021 in the English language using the following keywords alone or in combination: anaphylaxis, non-anaphylaxis, anaphylactic reaction, nonanaphylactic reaction, anaphylactic/anaphylactoid shock, hypersensitivity, allergy reaction, allergic reaction, immunology reaction, immunologic reaction, angioedema, loss of consciousness, generalized erythema, urticaria, urticarial rash, cyanosis, grunting, stridor, tachypnoea, wheezing, tachycardia, abdominal pain, diarrhea, nausea, vomiting and tryptase. We included studies in adults of all ages in all healthcare settings. Effect sizes of prevalence were pooled with 95% confidence intervals (CIs). To minimize heterogeneity, we performed sub-group analyses.

RESULTS

Of the 1,734 papers that were identified, 26 articles were included in the systematic review (8 case report, 5 cohort, 4 case series, 2 randomized controlled trial and 1 randomized cross-sectional studies) and 14 articles (1 cohort, 2 case series, 1 randomized controlled trial and 1 randomized cross-sectional studies) were included in meta-analysis. Studies involving 26,337,421 vaccine recipients [Pfizer-BioNTech (n = 14,505,399) and Moderna (n = 11,831,488)] were analyzed. The overall pooled prevalence estimate of anaphylaxis to both vaccines was 5.0 (95% CI 2.9 to 7.2, I2 = 81%, p =  < 0.0001), while the overall pooled prevalence estimate of nonanaphylactic reactions to both vaccines was 53.9 (95% CI 0.0 to 116.1, I2 = 99%, p =  < 0.0001). Vaccination with Pfizer-BioNTech resulted in higher anaphylactic reactions compared to Moderna (8.0, 95% CI 0.0 to 11.3, I2 = 85% versus 2.8, 95% CI 0.0 to 5.7, I2 = 59%). However, lower incidence of nonanaphylactic reactions was associated with Pfizer-BioNTech compared to Moderna (43.9, 95% CI 0.0 to 131.9, I2 = 99% versus 63.8, 95% CI 0.0 to 151.8, I2 = 98%). The funnel plots for possible publication bias for the pooled effect sizes to determine the incidence of anaphylaxis and nonanaphylactic reactions associated with mRNA COVID-19 immunization based on mRNA vaccine type appeared asymmetrical on visual inspection, and Egger's tests confirmed asymmetry by producing p values < 0.05. Across the included studies, the most commonly identified risk factors for anaphylactic and nonanaphylactic reactions to SARS-CoV-2 vaccines were female sex and personal history of atopy. The key triggers to anaphylactic and nonanaphylactic reactions identified in these studies included foods, medications, stinging insects or jellyfish, contrast media, cosmetics and detergents, household products, and latex. Previous history of anaphylaxis; and comorbidities such as asthma, allergic rhinitis, atopic and contact eczema/dermatitis and psoriasis and cholinergic urticaria were also found to be important.

CONCLUSION

The prevalence of COVID-19 mRNA vaccine-associated anaphylaxis is very low; and nonanaphylactic reactions occur at higher rate, however, cutaneous reactions are largely self-limited. Both anaphylactic and nonanaphylactic reactions should not discourage vaccination.

Allergy to COVID-19 vaccines: A current update

Adverse allergic reactions due to the administration of the vaccines developed for the protection of coronavirus disease 2019 (COVID-19) have been reported since the initiation of the vaccination campaigns. Current analyses provided by the Center for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) in the United States have estimated the rates of anaphylactic reactions in 2.5 and 11.1 per million of mRNA-1273 and BNT162b2 vaccines administered, respectively. Although rather low, such rates could have importance due to the uncommon fact that a large majority of the world population will be subjected to vaccination with the aforementioned vaccines in the following months and vaccination will most likely be necessary every season as for influenza vaccines. Health regulators have advised that any subject with a previous history of allergy to drugs or any component of the vaccines should not be vaccinated, however, certain misunderstanding exists since allergy to specific excipients in drugs and vaccines are in occasions misdiagnosed due to an absence of suspicion to specific excipients as allergenic triggers or due to inaccurate labeling or nomenclature. In this review, we provide an updated revision of the most current data regarding the anaphylactic reactions described for BNT162b2 vaccine, mRNA-1273 vaccine, and AZD1222 vaccine. We extensively describe the different excipients in the vaccines with the potential to elicit systemic allergic reactions such as polyethylene glycol (PEG), polysorbates, tromethamine/trometamol, and others and the possible immunological mechanisms involved.

Progress in study on the association between HLA genetic variation and adverse drug reactions

The human leukocyte antigen (HLA) molecules encoded within the human major histocompatibility complex are a group of highly conserved cell surface proteins, which are related to antigen recognition. HLA genes display a high degree of genetic polymorphism, which is the basis of individual differences in immunity. Specific HLA genotypes have been highly associated with typical adverse drug reactions. HLA-A*31:01 and HLA-B*15:02 are associated with carbamazepine-induced severe cutaneous adverse reactions, HLA-B*57:01 is related to abacavir-induced drug-induced hypersensitivity syndrome and flucloxacillin/pazopanib-induced drug-induced liver injury, while HLA-B*35:01 is a potential biomarker for predicting polygonum multiflorum-induced liver injury. It is not clear how small drug molecules to interact with HLA molecules and T cell receptors (TCR). There are four mechanistic hypotheses, including the hapten/prohapten theory, the pharmacological interaction concept, the altered peptide repertoire model, and the altered TCR repertoire model.

Obesity markers in patients with drug allergy and body fat as a predictor

BACKGROUND

Obesity is a chronic low-grade inflammation state associated with several diseases.

OBJECTIVE

To investigate a potential link between drug allergy and obesity, exploring whether the association depends on the type (immediate vs nonimmediate) or the severity of the reaction.

METHODS

Anthropometric measurements, bioimpedance, and biochemical analysis, including serum adipokines, were performed in 90 consecutive adult patients studied for suspected drug allergy. Logistic regression models were developed to identify predictors of drug allergy.

RESULTS

A total of 84 patients completed the diagnostic workup (78.6% women; mean age 39.58 ± 13.3 years). Drug allergy was confirmed in 39 patients and excluded in 45 (controls). Regarding body mass index, 42.2% had normal weight and 55.3% were overweight/obese. A total of 58% of women and 41% of men fulfilled the criteria for central obesity. Patients with drug allergy exhibited considerably higher body mass index, waist and hip circumferences, waist-hip ratio, fat mass, body fat percentage (BFP), trunk fat mass, leptin levels, and leptin-adiponectin ratio than controls. Similar results were obtained in the subgroup with immediate reactions, compared with the nonimmediate or unknown reactions. The higher the BFP and the number of reactions, the greater the odds of drug allergy (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.01-1.14 and OR, 2.82; 95% CI, 1.31-6.10, respectively). An immediate reaction was also a predictor of drug allergy (OR, 3.81; 95% CI, 1.30-11.14, P = .02), compared with nonimmediate or unknown reactions. In patients with drug allergy, BFP was a predictor of having an immediate reaction (OR, 1.12; 95% CI, 1.02-1.24, P = .02).

CONCLUSION

Our study illustrates, for the first time, evidence of a link between obesity and drug allergy, particularly immediate reactions. The BFP emerged as a potential predictor of drug allergy.

N-acetyltransferase 2 enzyme genotype-phenotype discordances in both HIV-negative and HIV-positive Nigerians

BACKGROUND

The N-acetyltransferase 2 (NAT2) enzyme has been understudied in Nigerians including genotype-phenotype association studies.

OBJECTIVE

The aim of this study was NAT2 haplotype identification and genotype-phenotype investigations in HIV-positive and HIV-negative Nigerians.

PATIENTS AND METHODS

Phenotypes included self-reported sulphonamide hypersensitivity survey, experimental and computational NAT2 phenotyping. The NAT2 gene was amplified by PCR. Gene sequencing used ABI 3730 and Haploview 4.2 for haplotype reconstruction. Genotype-phenotype analyses used the χ P-value and odds ratio with a 95% confidence interval.

RESULTS

Self-reported sulphonamide hypersensitivity showed a prevalence of 3.1 and 12.4% in HIV-positive and HIV-negative Nigerians, respectively. NAT2 genetic variants 191G>A, 282C>T, 341T>C, 481C>T, 590G>A, 803A>G and 857G>A were not significantly different between both groups (odds ratio=0.87; 95% confidence interval: 0.54-1.38, P=0.55). Nine haplotypes: NAT2*4, NAT2*12A, NAT2*13A, NAT2*5B, NAT2*6A, NAT2*7B, NAT2*5C, NAT2*14B and NAT2*14A had frequencies more than 1%, whereas NAT2*12B had 1.1% in the HIV-positive and 0.4% in the HIV-negative group. Overall, slow acetylator haplotypes made up 68%. The NAT2*12 signature single-nucleotide polymorphism was in high linkage disequilibrium with signature single-nucleotide polymorphism for NAT2*13 (D'=0.97, r=0.61) and NAT2*5 (D'=0.98, r=0.64). Genotype-phenotype association analysis showed haplotypes NAT2*13A, NAT2*5C, NAT2*7B and NAT2*14A to be associated strongly with the slow metabolic phenotype (P=0.002, 0.029, 0.032 and 0.050, respectively). Computational phenotypes were similar, with 30.9, 66 and 3.1% for slow, intermediate and rapid acetylators, respectively, among HIV-positive Nigerians and 31.2, 66.3 and 2.5% among the HIV-negative group. Overall, slow phenotypes made up 31%.

CONCLUSION

NAT2 haplotype frequencies are similar in Nigerians, irrespective of HIV status, but genotype-phenotype discordances exist.

Photosensitivity and cancer immune-targeted therapies

The novel group of immunological agents used for solid tumors has importantly improved the quality of life and the survival rate of oncologic patients. Compared to conventional chemotherapy agents, they are more effective and less toxic. However, adverse cutaneous effects are commonly observed, and in some cases, they may induce treatment discontinuation, with heavy impact on patient prognosis. Among these, photosensitive reactions, either phototoxic or photoallergic, are increasing. Much remains to be clarified on the understanding of their prevention, diagnosis, and management. We have reviewed the literature about photosensitive reactions occurring during oncologic immunotherapies. Early dermatological diagnosis and adequate management, with oncologist's cooperation, is fundamental.

Allergic contact dermatitis of both eyes caused by alcaftadine 0.25%: a case report

Background

To report the first case of allergic contact dermatitis (ACD) associated with alcaftadine 0.25% ophthalmic solution.

Case presentation

The patient was a 51-year-old woman with no previous history of side effects to ophthalmic antihistamine agents. She had been prescribed alcaftadine 0.25% for allergic conjunctivitis. On first application of the medication, she did not experience any cutaneous reaction. One day later, after the second alcaftadine 0.25% application, both eyelids became swollen, and erythematous changes were evident. On slit-lamp examination, conjunctival injection was noted in the absence of conjunctival swelling or any other findings. Fundus examination was unremarkable. To evaluate the cause of ACD, a patch test was performed and 48 h later was noted to be positive for alcaftadine 0.25%. Based on the positive patch test, the patient was diagnosed with ACD caused by alcaftadine 0.25%. After 9 days of treatment, the swelling and erythema completely resolved.

Conclusions

Although there have been no previous reports of alcaftadine 0.25%-associated ACD, it should be suspected in patients with swelling and erythematous change of both eyes after using alcaftadine 0.25%.

Covalent Heterobivalent Inhibitor Design for Inhibition of IgE-Dependent Penicillin Allergy in a Murine Model

Drug allergies occur when hapten-like drug metabolites conjugated to serum proteins, through their interactions with specific IgE, trigger allergic reactions that can be life threatening. A molecule termed covalent heterobivalent inhibitor (cHBI) was designed to specifically target drug hapten-specific IgE to prevent it from binding drug-haptenated serum proteins. cHBI binds the two independent sites on a drug hapten-specific Ab and covalently conjugates only to the specific IgE, permanently inhibiting it. The cHBI design was evaluated via ELISA to measure cHBI-IgE binding, degranulation assays of rat basophil leukemia cells for in vitro efficacy, and mouse models of ear swelling and systemic anaphylaxis responses for in vivo efficacy. The cHBI design was evaluated using two separate models: one specific to inhibit penicillin G-reactive IgE and another to inhibit IgE specific to a model compound, dansyl. We show that cHBI conjugated specifically to its target Ab and inhibited degranulation in cellular degranulation assays using rat basophil leukemia cells. Furthermore, cHBIs demonstrated in vivo inhibition of allergic responses in both murine models. We establish the cHBI design to be a versatile platform for inhibiting hapten/IgE interactions, which can potentially be applied to inhibit IgE-mediated allergic reactions to any drug/small-molecule allergy.

Relation Between Attention-Deficit Hyperactivity Disorder and IgE-Dependent Allergy in Pediatric Patients

Food allergy is a common condition in children and adolescent, remitting with time. Few clinical studies have emphasized the link between food allergies and psychosocial conditions, suggesting a profound impact of atopic diseases on the development of attention-deficit hyperactivity disorder (ADHD) in children. The objective of this study was to compile and assess available studies on the comorbidity or causality between ADHD and atopic food allergy in children. We discuss epidemiology, interrelated mechanisms, and potential dietary interventions in the management of children with ADHD.

Comorbidities in Childhood Celiac Disease: A Phenome Wide Association Study Using the Electronic Health Record

OBJECTIVES

Celiac disease (CD) is associated with a variety of extraintestinal autoimmune and inflammatory findings that manifest clinically as symptoms and comorbidities. Understanding these comorbidities may improve identification of the disease and prevent sequelae. In this study, we use an unbiased electronic health record (EHR)-based Phenome Wide Association Study (PheWAS) method to confirm known comorbidities, discover novel associations and enhance characterization of the clinical presentation of CD in children.

METHODS

Data were extracted from the Nationwide Children's Hospital EHR. Confirmed CD cases (n = 433) were matched with 4330 randomly selected controls. Utilizing an EHR-based PheWAS method to analyze associations of phenotypes with CD, we conducted an unbiased screening of all International Classification of Diseases, 10th revision diagnostic codes and examined significance by performing Fisher's Exact tests. We further tested for the association between CD and 14 previously identified comorbidities in an a priori fashion.

RESULTS

We found 45 International Classification of Diseases, 10th revision codes significantly associated with CD. Thirteen are known comorbidities and nine are expected symptoms of CD, thus validating our study methods. Further investigation found symptoms that characterized CD clinically and discovered a significant association between eosinophilic disorders of the esophagus and CD. Of 14 previously identified comorbidities, 8 were significantly associated with CD.

CONCLUSIONS

An EHR-based PheWAS method is a powerful, efficient, and cost-effective method to screen for possible CD comorbidities and validate associations at the population level. Ours is the first PheWAS of CD to confirm a significant association of eosinophilic disorders of the esophagus with CD in a controlled study.

Identification of T-cell epitopes from benzylpenicillin conjugated to human serum albumin and implication in penicillin allergy

BACKGROUND

There is in vitro evidence that T cells from allergic patients react to benzylpenicillin-human serum albumin (BP-HSA) bioconjugates. Our group has recently shown the existence of naïve CD4⁺ T cells recognizing BP-HSA in healthy donors. However, BP-haptenated peptides from HSA participating in the immunization of allergic patients have never been identified. The purpose of the present study is to identify immunodominant BP-haptenated peptides from HSA involved in immunization of patients to BP and to refine the frequency calculation of naïve CD4⁺ T cells recognizing BP.

METHODS

Co-cultures were established with CD4⁺ T cells from non-allergic donors and mature autologous dendritic cells (DCs) loaded with BP-HSA or BP-haptenated peptides from HSA. The CD4⁺ T-cell response specific for BP-HSA or for individual BP-haptenated peptides was measured using an interferon-γ (IFN-γ) ELISpot assay. The frequency of BP-specific CD4⁺ T cells was then calculated using the Poisson distribution. BP-HSA and BP-haptenated peptides recognition by allergic patients was evaluated on peripheral blood mononuclear cells (PBMCs) using a lymphocyte transformation test (LTT).

RESULTS

Results showed that BP-HSA and BP-haptenated peptides were recognized by naïve T cells from 15/16 and 13/14 tested healthy donors, respectively. Most donors responded to 3 peptides with BP covalently bound on lysines 159, 212, and 525. Two of these benzylpenicilloylated peptides (lysines 159 and 525) were also found to induce PBMCs proliferation in patients with allergic reaction to penicillins.

CONCLUSION

This study identifies and characterizes for the first time the BP-haptenated peptides from HSA involved in the immunization of patients to penicillins.

Drug-Induced Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis Call for Optimum Patient Stratification and Theranostics via Pharmacogenomics

The Global Genomic Medicine Collaborative, a multinational coalition of genomic and policy experts working to implement genomics in clinical care, considers pharmacogenomics to be among the first areas in genomic medicine that can provide guidance in routine clinical practice, by linking genetic variation and drug response. Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe life-threatening reactions to medications with a high incidence worldwide. Genomic screening prior to drug administration is a key opportunity and potential paradigm for using genomic medicine to reduce morbidity and mortality and ultimately eliminate one of the most devastating adverse drug reactions. This review focuses on the current understanding of the surveillance, pathogenesis, and treatment of SJS/TEN, including the role of genomics and pharmacogenomics in the etiology, treatment, and eradication of preventable causes of drug-induced SJS/TEN. Gaps, unmet needs, and priorities for future research have been identified for the optimal management of drug-induced SJS/TEN in various ethnic populations. Pharmacogenomics holds great promise for optimal patient stratification and theranostics, yet its clinical implementation needs to be cost-effective and sustainable.

Peripheral Vasculitic Neuropathy Associated With Minocycline Use

We describe 2 patients presenting with multiplex mononeuritis, associated with skin manifestation, secondary to minocycline-induced vasculitis. One of the cases is associated neither with lupus nor polyarteritis nodosa. An extensive laboratory workup ruled out any possible underlying immunologic disorder. Electrodiagnostic studies were conducted to show axonal neuropathy in patchy and multifocal distribution consistent with multiplex mononeuritis. This diagnosis was confirmed with nerve biopsy. Withdrawing from the offending medication, minocycline, improved the patients' clinical condition and the quantitative serological measures.

An Updated Review of the Molecular Mechanisms in Drug Hypersensitivity

Drug hypersensitivity may manifest ranging from milder skin reactions (e.g., maculopapular exanthema and urticaria) to severe systemic reactions, such as anaphylaxis, drug reactions with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS), or Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN). Current pharmacogenomic studies have made important strides in the prevention of some drug hypersensitivity through the identification of relevant genetic variants, particularly for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). The associations identified by these studies are usually drug, phenotype, and ethnic specific. The drug presentation models that explain how small drug antigens might interact with HLA and T cell receptor (TCR) molecules in drug hypersensitivity include the hapten theory, the p-i concept, the altered peptide repertoire model, and the altered TCR repertoire model. The broad spectrum of clinical manifestations of drug hypersensitivity involving different drugs, as well as the various pathomechanisms involved, makes the diagnosis and management of it more challenging. This review highlights recent advances in our understanding of the predisposing factors, immune mechanisms, pathogenesis, diagnostic tools, and therapeutic approaches for drug hypersensitivity.

A New Pathway for Protein Haptenation by β-Lactams

The covalent binding of β-lactams to proteins upon photochemical activation has been demonstrated by using an integrated approach that combines photochemical, proteomic and computational studies, selecting human serum albumin (HSA) as a target protein and ezetimibe (1) as a probe. The results have revealed a novel protein haptenation pathway for this family of drugs that is an alternative to the known nucleophilic ring opening of β-lactams by the free amino group of lysine residues. Thus, photochemical ring splitting of the β-lactam ring, following a formal retro-Staudinger reaction, gives a highly reactive ketene intermediate that is trapped by the neighbouring lysine residues, leading to an amide adduct. For the investigated 1/HSA system, covalent modification of residues Lys414 and Lys525, which are located in sub-domains IIIA and IIIB, respectively, occurs. The observed photobinding may constitute the key step in the sequence of events leading to photoallergy. Docking and molecular dynamics simulation studies provide an insight into the molecular basis of the selectivity of 1 for these HSA sub-domains and the covalent modification mechanism. Computational studies also reveal positive cooperative binding of sub-domain IIIB that explains the experimentally observed modification of Lys414, which is located in a barely accessible pocket (sub-domain IIIA).

Anaphylaxis after disinfection with 2% chlorhexidine wand applicator

A 54-year-old man with end-stage renal failure attended for dialysis. Within seconds of applying 2% w/v chlorhexidine (ChloraPrep 3 mL Wand Applicator) to the skin surrounding the insertion point of his dialysis catheter (Tesio catheter), he developed pruritus, urticaria, shortness of breath, hypotension and reduced responsiveness. Treatment for anaphylaxis was initiated with rapid improvement of his symptoms, and he made a full recovery. Allergy to chlorhexidine was confirmed with skin testing, and the patient was warned against all future exposure to chlorhexidine. Subsequent dialysis without chlorhexidine was uneventful.

Adverse Medication Reactions

Cutaneous adverse drug reactions (ADRs) are among the most frequent adverse reactions in patients receiving drug therapy. They have a broad spectrum of clinical manifestations, are caused by various drugs, and result from different pathophysiological mechanisms. Hence, their diagnosis and management is challenging.

Severe cutaneous ADRs comprise a group of diseases with major morbidity and mortality, reaching 30 % mortality rate in cases of Toxic Epidermal Necrolysis.

This chapter covers the terminology, epidemiology, pathogenesis and classification of cutaneous ADR, describes the severe cutaneous ADRs and the clinical and laboratory approach to the patient with cutaneous ADR and presents the translation of laboratory-based discoveries on the genetic predisposition and pathogenesis of cutaneous ADRs to clinical management guidelines.

Involvement of Histamine and RhoA/ROCK in Penicillin Immediate Hypersensitivity Reactions

The mechanism of penicillin immediate hypersensitivity reactions has not been completely elucidated. These reactions are generally considered to be mediated by IgE, but penicillin-specific IgE could not be detected in most cases. This study demonstrated that penicillin was able to cause vascular hyperpermeability in a mouse model mimicking clinical symptoms of penicillin immediate hypersensitivity reactions. The first exposure to penicillin also induced immediate edema and exudative reactions in ears and lungs of mice in a dose-dependent manner. Vasodilation was noted in microvessels in ears. These reactions were unlikely to be immune-mediated reactions, because no penicillin-specific IgE was produced. Furthermore, penicillin treatment directly elicited rapid histamine release. Penicillin also led to F-actin reorganization in human umbilical vein endothelial cells and increased the permeability of the endothelial monolayer. Activation of the RhoA/ROCK signaling pathway was observed in ears and lungs of mice and in endothelial cells after treatment with penicillin. Both an anti-histamine agent and a ROCK inhibitor attenuated penicillin immediate hypersensitivity reactions in mice. This study presents a novel mechanism of penicillin immediate hypersensitivity reactions and suggests a potential preventive approach against these reactions.

Anaphylactic-like reaction from trimethoprim-sulfamethoxazole in a patient with AIDS

We report a patient with AIDS who had an anaphylactic-like reaction from trimethoprim-sulfamethoxazole. Clinical suspicion of anaphylaxis should be considered in patients presenting with fever, hypotension, eosinophilia, rash, flushing or pulmonary infiltrates after initial exposure and re-exposure to the medication. This case highlights the need for healthcare professionals to be reminded of the association between this unusual antibiotic reaction resembling sepsis and HIV disease.

Pharmacogenetics of adverse reactions to antiepileptic drugs

INTRODUCTION

Adverse drug reactions (ADRs) are a major public health concern and a leading cause of morbidity and mortality in the world. In the case of antiepileptic drugs (AEDs), ADRs constitute a barrier to successful treatment since they decrease treatment adherence and impact patients' quality of life of patients. Pharmacogenetics aims to identify genetic polymorphisms associated with drug safety. This article presents a review of genes coding for drug metabolising enzymes and drug transporters, and HLA system genes that have been linked to AED-induced ADRs.

DEVELOPMENT

To date, several genetic variations associated with drug safety have been reported: CYP2C9*2 and *3 alleles, which code for enzymes with decreased activity, have been linked to phenytoin (PHT)-induced neurotoxicity; GSTM1 null alleles with hepatotoxicity induced by carbamazepine (CBZ) and valproic acid (VPA); EPHX1 polymorphisms with teratogenesis; ABCC2 genetic variations with CBZ- and VPA-induced neurological ADRs; and HLA alleles (e.g. HLA-B*15:02, -A*31:01, -B*15:11, -C*08:01) with cutaneous ADRs.

CONCLUSIONS

Published findings show that there are ADRs with a pharmacogenetic basis and a high interethnic variability, which indicates a need for future studies in different populations to gather more useful results for larger number of patients. The search for biomarkers that would allow predicting ADRs to AEDs could improve pharmacotherapy for epilepsy.

Drug allergies and implications for dental practice

Adverse reactions to medications prescribed or administered in dental practice can be worrying. Most of these reactions are somewhat predictable based on the pharmacodynamic properties of the drug. Others, such as allergic and pseudoallergic reactions, are generally unpredictable and unrelated to normal drug action. This article will review immune and nonimmune-mediated mechanisms that account for allergic and related reactions to the particular drug classes commonly used in dentistry. The appropriate management of these reactions will also be addressed.

Dapsone Hypersensitivity Syndrome in a Patient With Acquired Immunodeficiency Syndrome

Objective: A case of dapsone hypersensitivity syndrome (DHS) in an AIDS patient receiving dapsone for Pneumocystis pneumonia (PCP) prophylaxis is discussed. Case Summary: A 50-year-old Caucasian male with a history of AIDS was admitted with suspicion of pneumonia. The clinical presentation consisted of shortness of breath, occasional hemoptysis, odynophagia, skin rash, transaminitis, anemia, malaise, and peripheral neuropathy. His medications included nystatin, fluconazole, valacyclovir, and pantoprazole. For PCP prophylaxis, the patient was initiated on dapsone 100 mg daily approximately 4 weeks prior to admission. The patient was also on a 3-drug regimen for the treatment of mycobacterium avium complex: clarithromycin, rifabutin, and ethambutol. After extensive work up, DHS was diagnosed. Dapsone was immediately discontinued and the patient was started on intravenous methylprednisolone, gradually tapered, and transitioned to oral prednisone. On discontinuation of dapsone, the patient improved, evidenced by decreased need for oxygen and reversal of peripheral neuropathy, anemia, and transaminitis. The patient’s skin rash improved within a few days. An objective causality assessment, with the Naranjo scale, suggests that DHS was probably related to dapsone. Discussion: Our patient only exhibited some of the classic symptoms observed in DHS such as skin eruptions, malaise, hepatic failure, and hemolytic anemia. The patient, however, did not present with lymphadenopathy and fever commonly noted in DHS, which may be attributed to his immunosuppressed state, evidenced by a CD4 count of 7 cell/mm3. Conclusions: A patient on dapsone for PCP prophylaxis was diagnosed with DHS. Clinicians and patients should be educated on risk factors and clinical presentation of DHS so that when initial symptoms appear they can be treated promptly. Clinicians should also be aware that patients infected with HIV/AIDS may not present with all the classic symptoms of DHS due to their immunocompromised state. Therefore, practitioners should be vigilant when initiating dapsone in this patient population.

Skin test reactivity to female sex hormones in women with primary unexplained recurrent pregnancy loss

The objective was to examine the hypothesis that primary unexplained recurrent pregnancy loss might be associated with an inappropriate immunologically mediated response to progesterone and/or estrogen. This prospective study included 47 women with two or more documented consecutive early pregnancy losses of unknown etiology, and no previous history of deliveries. Intradermal skin testing was performed in the luteal phase of the cycle (days 16-20) using estradiol benzoate, progesterone, and a placebo of refined sesame oil. Immediate (20 min) and late (24h and 1 week) skin test readings for all cases were compared with those of 12 parous women of comparable age with no history of spontaneous miscarriages, premenstrual disorders, pregnancy, or sex hormone-related allergic or autoimmune diseases. Main outcome measure was skin test reactivity to estradiol and/or progesterone. Immediate skin test reactivity to both hormones was observed among half of the cases at 20 min. A papule after 24h, which persisted for up to 1 week, was observed among 32 (68.1%) and 34 (72.3%) cases at the sites of estrogen and progesterone injection, respectively. 55.3% of cases had combined skin test reactivity to both estradiol and progesterone at 1 week. All women in the control group showed absence of skin test reactivity for both estradiol and progesterone at 20 min, 24h, and 1 week. None of the subjects in either group showed skin test reactivity to placebo. There is an association between primary unexplained recurrent pregnancy loss and skin test reactivity to female sex hormones.

[Anaphylactic shock from an iodine contrast medium: role of the allergy check-up in one case]

Anaphylactoid reactions to iodine contrast media are rare but serious, possibly life-threatening and calling an appropriate and urgent care. The physiopathological mechanism of these reactions remains to be fully elucidated. This reaction is still mostly called "pseudoallergic" in the literature. However, recent papers emphasise that a true allergic process is more frequent than previously expected. They also insist on the interest of running allergy tests including skin testing. We report the case of an anaphylactic shock to iodine contrast media, occurring during coronary angiography. We performed an allergy check-up and found the culprit allergen. We also evidenced a cross-reaction to another contrast media from the similar group. On the other hand, there was no reaction to contrast media of other types. With these results, another coronary angiography could be performed without any adverse event. When hypersensitivity reactions to iodine contrast media occur, it is mandatory to perform a complete allergy check-up. This will help determine the precise mechanism of the reaction and find the culprit allergen.

Cutaneous side effects of antiosteoporosis treatments

Cutaneous adverse reactions are reported for many therapeutic agents and, in general, are observed in between 0% and 8% of treated patients depending on the drug. Antiosteoporotic agents are considered to be safe in terms of cutaneous effects, however there have been a number of case reports of cutaneous adverse reactions which warrant consideration. This was the subject of a working group meeting of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis in April 2009, which focused on the impact of cutaneous adverse reactions and drug-induced hypersensitivity in the management of postmenopausal osteoporosis. This position paper was drafted following these discussions and includes a flowchart for their recognition. Cutaneous adverse reactions observed with antiosteoporotic agents were reviewed and included information from case reports, regulatory documents and pharmacovigilance. These reactions ranged from benign effects including exanthematous or maculopapular eruption (drug rash), photosensitivity and urticaria, to the severe and potentially life-threatening reactions of angioedema, drug rash with eosinophilia and systemic symptoms (DRESS), Stevens Johnson syndrome and toxic epidermal necrolysis. A review of the available evidence demonstrates that cutaneous adverse reactions occur with all commonly used antiosteoporotic treatments. Notably, there are reports of Stevens Johnson syndrome and toxic epidermal necrolysis for bisphosphonates, and of DRESS and toxic epidermal necrolysis for strontium ranelate. These severe reactions remain very rare (<1 in 10,000 cases). In general, with proper management and early recognition, including immediate and permanent withdrawal of the culprit agent, accompanied by hospitalization, rehydration and systemic corticosteroids if necessary, the prognosis is positive.

Drug-induced interstitial lung disease: mechanisms and best diagnostic approaches

Drug-induced interstitial lung disease (DILD) is not uncommon and has many clinical patterns, ranging from benign infiltrates to life-threatening acute respiratory distress syndrome. There are two mechanisms involved in DILD, which are probably interdependent: one is direct, dose-dependent toxicity and the other is immune-mediated. Cytotoxic lung injury may result from direct injury to pneumocytes or the alveolar capillary endothelium. Drugs can induce all types of immunological reactions described by Gell and Coombs; however, most reactions in immune-mediated DILD may be T cell-mediated.

DILD can be difficult to diagnose; diagnosis is often possible by exclusion alone. Identifying the causative drug that induces an allergy or cytotoxicity is essential for preventing secondary reactions.

One method to confirm the diagnosis of a drug-induced disease is re-exposure or re-test of the drug. However, clinicians are reluctant to place patients at further risk of illness, particularly in cases with severe drug-induced diseases. Assessment of cell-mediated immunity has recently increased, because verifying the presence or absence of drug-sensitized lymphocytes can aid in confirmation of drug-induced disease. Using peripheral blood samples from drug-allergic patients, the drug-induced lymphocyte stimulation test (DLST) and the leukocyte migration test (LMT) can detect the presence of drug-sensitized T cells. However, these tests do not have a definite role in the diagnosis of DILD. This study explores the potential of these new tests and other similar tests in the diagnosis of DILD and provides a review of the relevant literature on this topic.

Drug hypersensitivity reactions targeting the skin in dogs and cats

Adverse drug reactions (ADRs) can be dose dependent or idiosyncratic. Most idiosyncratic reactions are believed to be immune-mediated; such drug hypersensitivities and allergies are unpredictable. Cutaneous reactions are the most common presentation of drug allergies. In veterinary medicine it can be difficult to assess the true prevalence of adverse drug reactions, although reports available suggest that they occur quite commonly. There are multiple theories that attempt to explain how drug allergies occur, because the pathogenesis is not yet well understood. These include the (pro)-hapten hypothesis, the Danger Theory, the pi concept, and the viral reactivation theory. Cutaneous drug allergies in veterinary medicine can have a variety of clinical manifestations, ranging from pruritus to often fatal toxic epidermal necrolysis. Diagnosis can be challenging, as the reactions are highly pleomorphic and may be mistaken for other dermatologic diseases. One must rely heavily on history and physical examination to rule out other possibilities. Dechallenge of the drug, histopathology, and other diagnostic tests can help to confirm the diagnosis. New diagnostic tools are beginning to be used, such as antibody or cellular testing, and may be used more in the future. There is much yet to learn about drug allergies, which makes future research vitally important. Treatment of drug allergies involves supportive care, and additional treatments, such as immunosuppressive medications, depend on the manifestation of the disease. Of utmost importance is to avoid the use of the incriminating drug in future treatment of the patient, as subsequent reactions can be worse, and ultimately can prove fatal.

Is drug allergy less prevalent than previously assumed? A 5-year analysis

BACKGROUND

Rashes are a frequent conundrum in clinical practice as they may be reactive, drug induced or disease specific. Identification of the culprit drug is important as re-exposure may be harmful or even life-threatening and unnecessary avoidance of 'innocent' drugs leads to limitations of treatment options.

OBJECTIVE

To objectify the cause of suspected cutaneous drug reactions in a large patient population.

METHOD

Over 5years (2006-10), 612 patients with suspected cutaneous drug reactions were evaluated. Histology was assessed. About 200 patients were invited for complete work-up with skin tests (prick/intracutaneous testing and scratch/patch as indicated) and, if necessary, lymphocyte transformation tests (LTT). In special cases, drug provocation tests were conducted.

RESULTS

A total number of 141 cases with suspected drug reaction underwent full work-up (age 6-86years; 75% female, 25% male). In 107 cases (76%) a drug was identified whereas 34 (24%) were reactive rashes or had other causes. Mostly, cutaneous drug reactions were maculopapular rashes, urticaria/angio-oedema; less frequently, acute generalized exanthematous pustulosis, drug reaction with eosinophilia and systemic symptoms, systemic drug-related intertriginous and flexural exanthema, toxic epidermal necrolysis and fixed drug eruptions were present. Of all the cutaneous drug reactions investigated, 39·8% were caused by antibiotics, 21·2% by anti-inflammatories, 7·6% by contrast media and 31·4% by others (oral antidiabetics, antimycotics, antipsychotics, antiepileptics and others).

CONCLUSION

Clinical assessment overestimates the role of drug allergies in cutaneous reactions. Assessment of suspected drug reactions can be greatly improved by thorough evaluation including dermatological and allergological work-up with skin testing and assays such as LTT.

Safety of long-term bisphosphonate therapy for the management of osteoporosis

Drugs in the bisphosphonate class are the most commonly prescribed therapeutic agents for the treatment of osteoporosis. Prospective, randomized, placebo-controlled clinical trials have demonstrated efficacy in reducing fracture risk, with favourable safety profiles, in women with postmenopausal osteoporosis. However, long-term use in clinical practice has been associated with reports of undesirable events not previously recognized. These have included gastrointestinal intolerance, osteonecrosis of the jaw, atypical femur fractures, oesophageal cancer, atrial fibrillation and chronic musculoskeletal pain. Physicians must be alert to newly recognized safety concerns, understand the level of evidence supporting them and be able to effectively communicate the balance of expected benefit and potential risk to patients. Usually, post-marketing adverse events are first presented as case reports or observational studies with variable levels of supporting evidence for plausibility, pathophysiology and causality. Widespread coverage in the news media, which can be alarming to patients and their physicians, may not present a balanced view of the proven benefits, the uncertain risks of therapy and the relative magnitude of these events. There may be confusion about the risks associated with bisphosphonate use for the treatment of osteoporosis versus treatment of other conditions, such as cancer, which typically involves a very different patient population and different doses or frequency of drug administration. Often reports of possible adverse events do not provide information on the number of patients exposed to the drug in proportion to the reported adverse event, or do not describe the incidence of the adverse event in a comparator population not exposed to the drug. Gastrointestinal intolerance with oral bisphosphonates, and hypocalcaemia, acute phase reactions and renal toxicity with intravenous bisphosphonates are characterized by biological plausibility and demonstration of causality. Safety concerns with uncertain biological plausibility and unproven causality include osteonecrosis of the jaw, atypical femur fractures, oesophageal cancer and ocular inflammation. Suspected concerns that are unlikely to be causally related include atrial fibrillation and hepatotoxicity. When making the decision to use a bisphosphonate for the treatment of osteoporosis, the balance between benefit and potential risks according to clinical circumstances of each patient should be considered.