Amoxil for tooth infection

Among other complications, this can spread the infection.

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Cutaneous manifestations are the most common presentation of allergic drug reactions. Diagnosis of drug allergy is largely based on clinical history because diagnostic tests are limited. Most patients who are labelled as having penicillin allergy can tolerate penicillins after allergy evaluation.

Cross-reactivity between cephalosporins and penicillins is rare.

Maculopapular rashes with amoxicillin are common and not an absolute contraindication for future use.

Adverse

Health Canada has documented an increase in reported adverse drug reactions, with nearly 30 000 reports of adverse drug reactions in 2009 (up 35% from the year before).5 In addition, adverse drug reactions are more common among older patients.

The Canadian Institute for Health Information (CIHI) reported that patients 65 years or older accounted for 57.6% of hospital admissions related to adverse drug reactions in Canada between 2006/07 and 2011/12, even though they accounted for only 14.2% of the Canadian population.6.

Adverse drug reactions are defined by the World Health Organization (WHO) as, “all intended pharmacologic effects of a drug except therapeutic failures, intentional over-dosage, abuse of the drug, or errors in administration.”1 The WHO defines adverse drug events as “an injury resulting from medical intervention related to a drug,” which, in contrast to adverse drug reactions, also includes in its definition errors in medication use, such as overdose.2.

In this review, we focus on allergic drug reactions and address key issues in diagnosis and management.

The articles referenced in this review include guidelines, cohort and case–control studies, and surveys (Box 1). We used recent American and international practice parameters and guidelines as primary bases to inform this review, supplemented with a search for systematic reviews for supporting information. Additional clinical points or examples are based on reviews, case–control and cohort studies, and surveys.

Where possible, we selected the most recent articles and the articles with the most robust level of evidence. Adverse drug reactions can be classified into predictable (“type A”) and unpredictable (“type B”) reactions.7 Predictable reactions account for 80% of all adverse drug reactions; they are common, dose-dependent and caused by the pharmacologic actions of the drug.1 In contrast, unpredictable reactions are uncommon, independent of dose and unrelated to pharmacologic effects of the drug (Table 1).1 Allergic drug reactions account for about 5%–10% of adverse drug reactions overall.9 Although the term “drug allergy” has often been used exclusively for immunoglobulin E (IgE)-mediated reactions, more recently, an expert panel on drug allergy discussed whether or not the term drug allergy should also include other forms of hypersensitivity reactions that are not IgE mediated.7. Classification of unpredictable adverse drug reactions1 , 8. What are the clinical manifestations of allergic drug reactions?

Although allergic reactions to medications can affect any organ system, cutaneous manifestations are by far the most common.8 , 10 A 2017 meta-analysis and systematic review of 53 studies (126 306 participants) found cutaneous manifestations to be present in 68.2% of allergic drug reactions (with anaphylactic or systemic reactions in 10.8%).11 Determining the characteristics of the cutaneous manifestation, if present, is one of the strongest diagnostic clues in a drug-induced allergic reaction. A 2016 review on cutaneous allergic drug reactions noted that most of these eruptions are benign in nature.12 The most common cutaneous eruption is a generalized maculopapular exanthem, which accounts for up to 90% of all cutaneous eruptions caused by drugs.4 , 13 , 14 The most severe reactions are Stevens–Johnson syndrome and toxic epidermal necrolysis.8 Table 2 describes clinical features of the more common types of allergic drug reactions.

Clinical features of drug hypersensitivity reactions1 , 7 , 8 , 10 , 13. The approach to diagnosis begins with the patient’s medical history, which may identify the etiology of the reaction, identify drug allergy as a possible cause of symptoms and provide details suggesting the possible type of drug-induced allergic reaction. Table 3 provides a list of useful components of the medical history.

In particular, establishing the time frame of the reaction (i.e., time of onset and its duration), the constellation of symptoms, previous exposure and underlying conditions as risk factors are essential in arriving at a diagnosis.

The Naranjo Adverse Drug Reaction Probability Scale can be used, based on the patient’s history, as a validated probability scale to help determine the likelihood that the symptoms described represent an adverse drug reaction.16 This scale based on 10 questions is relatively simple to use and is frequently cited when reporting new drug allergic reactions in the literature, but it is not used commonly in clinical practice.

Useful components of the medical history1 , 4 , 7 , 15.

Laboratory investigations are supportive and not confirmatory for most allergic drug reactions.

The National Institute for Health and Care Excellence recommends obtaining serum tryptase levels in the diagnosis of a potential IgE-mediated reaction, because elevated serum tryptase is relatively specific, especially if serial levels normalize, although this is based on low-quality evidence largely from observational studies.17 Serum eosinophilia supports a diagnosis of an

IgE-mediated

Other laboratory investigations (e.g., liver enzymes, renal function, complete blood cell count) may determine involvement of internal organs, in particular with severe nonimmediate drug-induced allergic reactions. Testing for autoantibodies is useful if there is concern about vasculitis (antineutrophil cytoplasmic antibody) or drug-induced lupus (antihistone levels in systemic drug-induced lupus,

and

Patients have been reported to tolerate both oral doses of penicillin1 , 8 and, according to a recent retrospective review, repeated intravenous penicillin without immediate hypersensitivity reactions.20. In vitro serum-specific IgE assays are available for some common antibiotics; however, their sensitivity and

specificity

Download figure Open in new tab Download powerpoint.

Maculopapular exanthema in drug reaction with eosinophilia and systemic symptoms.

Download figure Open in new tab Download powerpoint. Download figure Open in new tab Download powerpoint. For some nonimmediate reactions, in particular contact dermatitis, fixed drug eruption and maculopapular exanthem, skin patch testing (i.e., placing the allergen on the back at a nonirritating concentration under an aluminum disk) has been reported.1 , 23 In North America, it is not used commonly in the more severe nonimmediate drug reactions, such as Stevens–Johnson syndrome, toxic epidermal necrolysis or drug reaction with eosinophilia and systemic symptoms.8 However, in Europe, both patch testing and delayed intradermal testing (i.e., the result is read days later) are used for nonimmediate reactions, including severe reactions.24 , 25 A recent retrospective review of patch testing that included 260 patients who received treatment in a European dermatology clinic found that patch testing was safe and specific, even for severe nonimmediate reactions.26.

In most cases of drug allergy, validated skin or laboratory tests are not available.

For patients in whom the likelihood of drug allergy is deemed low (e.g., remote reaction, benign rash), a drug challenge can be performed by an allergist. If the history is not indicative of an allergy (e.g., headache), a full dose can be administered to confirm tolerance. In most circumstances, a graded challenge is performed, with the assistance of an allergist, that often involves the administration of two graded sub-therapeutic doses of the medication to the patient, with monitoring for an allergic reaction. A US guideline noted that drug challenges are contraindicated if the history is consistent with a severe drug reaction, such as Stevens–Johnson syndrome, toxic epidermal necrolysis or drug reaction with eosinophilia and systemic symptoms.1. In contrast, induction of drug tolerance (e.g., drug desensitization) involves providing increasing incremental doses of the medication to the patient over a period of hours to days, using different procedures based on the hypothesized mechanism of the reaction.

Induction of drug tolerance does modify the immune response to the medication temporarily while the patient remains on the medication. It effectively modifies the immune response to the medication, even though there is an underlying allergy.