Allergic drug reactions

An EAACI task force report: recognising the potential of the primary care physician in the diagnosis and management of drug hypersensitivity

Adverse drug reactions include drug hypersensitivity reactions (DHRs), which can be immunologically mediated (allergy) or non-immunologically mediated. The high number of DHRs that are unconfirmed and often self-reported is a frequent problem in daily clinical practice, with considerable impact on future prescription choices and patient health. It is important to distinguish between hypersensitivity and non-hypersensitivity reactions by adopting a structured diagnostic approach to confirm or discard the suspected drug, not only to avoid life-threatening reactions, but also to reduce the frequent over-diagnosis of DHRs. Primary care physicians are often the first point of contact for the sufferer of a reaction, as such they have a key role in deciding whether to discard the diagnosis or send the patient for further investigation. In this review, we highlight the importance of diagnosing DHRs, analysing in detail the role of primary care physicians. We describe the common patterns of DHRs and signs of its progression, as well as the indications and contraindications for referring the patient to an allergist. The diagnostic process is described and the possible tests are discussed, which often depend on the drug involved and the type of DHR suspected. We also describe recommendations regarding the avoidance of medication suspected to have caused the reaction and the use of alternatives.

A comprehensive 4-year survey of adverse drug reactions using a network-based hospital system

WHAT IS KNOWN AND OBJECTIVE

Spontaneous Adverse Drug Reaction Reporting Systems (ADRRS) provide early warnings or 'signals' for adverse drug reactions (ADRs). Our aim was to survey reports of ADRs made through our teaching-hospital-based pharmacovigilance system to identify the drugs most commonly associated with allergies and the types of immunological reactions reported.

METHODS

Adverse drug reactions records were retrieved from our network-based electronic notification system.

RESULTS AND DISCUSSION

Four hundred and seventy four reports of adverse drug effects were studied. 37.3% of the reactions were immune-mediated drug hypersensitivity reactions. True drug hypersensitivity reactions involving IgE-mediated drug allergies accounted for 15% of all reactions. Of the drug hypersensitivity reactions, more than half (67%) were morbilliform skin eruptions, whereas cases of urticaria accounted for 20%. Antibiotics (33% of cases) were the most commonly reported drug allergies, followed by non-steroidal anti-inflammatory drugs (13%) and anti-epileptic agents (10%).

WHAT IS NEW AND CONCLUSIONS

A hospital-based ADR reporting system can generate useful data. In our study, antibiotics accounted for the majority of drug allergies, particularly anaphylactic reactions. More cases of drug allergies were owing to cephalosporin allergies than penicillins. Anti-epileptic agents caused most of the severe drug hypersensitivity syndromes.

The use of penicillin skin testing to assess the prevalence of penicillin allergy in an emergency department setting

STUDY OBJECTIVE

Patient-reported penicillin allergies are often unreliable and can result in unnecessary changes in antibiotic therapy. Although penicillin allergy skin testing is commonly performed in allergy clinics, it has not been used in emergency departments (EDs) to verify self-reported allergies. We hypothesize that ED-based testing is possible and that the false-positive rate of patients with self-reported penicillin allergy are greater than 90%.

METHODS

This prospective observational cohort study enrolled a convenience sample of ED patients with a self-reported penicillin allergy. Patients were enrolled by one of 2 emergency physicians who performed skin prick and intracutaneous tests with penicillin major and minor determinants. The total testing time was 30 minutes. The proportion of false-positive self-reported allergies was computed with 95% confidence intervals (CIs) by using the score method.

RESULTS

A total of 150 patients (mean age 42 years; SD 16 years; 46% men; 47% black) were enrolled. The false-positive rate for self-reported penicillin allergy was 137 of 150 (91.3%; 95% CI 85.3% to 95.1%). There were no adverse reactions associated with penicillin skin testing. Compared with patients with a false-positive penicillin allergy result (confirmed by negative penicillin skin testing result), patients reporting a true penicillin allergy confirmed by positive penicillin skin test results tended to be more frequently men (61.5% versus 44.5%; Delta 17.0%; 95% CI -13.5% to 42%), black (69.2% versus 44.5%; Delta 24.7%; 95% CI -6.9% to 46.8%), and have no family history of drug allergy (7.7% versus 17.5%; Delta9.8%; 95% CI -20.9% to 20.4%), but self-reported other drug allergies more frequently (61.5% versus 38.7%; Delta 22.9%; 95% CI -7.7% to 47.5%).

CONCLUSION

Penicillin skin testing is feasible in the ED setting. A substantial number of patients who self-report a penicillin allergy do not exhibit immunoglobulin E-mediated sensitization to penicillin major and minor determinants. Penicillin testing in the ED may allow the use of more appropriate antibiotics for patients presenting with a history of penicillin allergy.

Harmless herbs? A review of the recent literature

Herbal medicines have become a popular form of therapy. They are often perceived as being natural and therefore harmless. This article reviews the recent literature on the adverse effects of herbal remedies. Examples of allergic reactions, toxic reactions, adverse effects related to an herb's desired pharmacological actions, possible mutagenic effects, drug interactions, drug contamination, and mistaken plant identities are provided. Because of underreporting, our present knowledge may well be just the "tip of the iceberg." Little is known about the relative safety of herbal remedies compared to synthetic drug treatments, although for some herbal remedies, the risks may be less than for conventional drugs.

A case of drug eruption due to simultaneous sensitization with three different kinds of drugs

We reported a case of drug eruption induced by combined treatment with three different kinds of drugs, amoxapine, mexiletine hydrochloride and cefaclor. A 63-year-old Japanese woman suffering from 11 years of standing reflex sympathetic dystrophy developed multiple erythematous papules on her trunk and extremities after taking 14 kinds of drugs. The provocation challenge produced positive reactions to amoxapine, mexiletine hydrochloride, and cefaclor, but was negative to the other drugs. We discussed the mechanism of simultaneous sensitization to three different kinds of drugs in our case.