Absence of cross-reactivity between sulfonamide antibiotics and sulfonamide nonantibiotics

Evaluation of polymorphisms in the sulfonamide detoxification genes NAT2, CYB5A, and CYB5R3 in patients with sulfonamide hypersensitivity

OBJECTIVE

To determine whether polymorphisms in the sulfonamide detoxification genes, CYB5A (encoding cytochrome b(5)), CYB5R3 (encoding cytochrome b(5) reductase), or NAT2 (encoding N-acetyltransferase 2) were over-represented in patients with delayed sulfonamide drug hypersensitivity, compared with control patients who tolerated a therapeutic course of trimethoprim-sulfamethoxazole without adverse event.

METHODS

DNA from 99 nonimmunocompromised patients with sulfonamide hypersensitivity who were identified from the Personalized Medicine Research Project at the Marshfield Clinic, and from 99 age-matched, race-matched, and sex-matched drug-tolerant controls, were genotyped for four CYB5A and five CYB5R3 polymorphisms, and for all coding NAT2 SNPs.

RESULTS

CYB5A and CYB5R3 SNPs were found at low allele frequencies (<3-4%), which did not differ between hypersensitive and tolerant patients. NAT2 allele and haplotype frequencies, as well as inferred NAT2 phenotypes, also did not differ between groups (60 vs. 59% slow acetylators). Finally, no difference in NAT2 status was found in a subset of patients with more severe hypersensitivity signs (drug reaction with eosinophilia and systemic symptoms) compared with tolerant patients.

CONCLUSION

We found no evidence of a substantial involvement of these nine CYB5A or CYB5R3 polymorphisms in sulfonamide hypersensitivity risk, although minor effects cannot be completely ruled out. Despite careful medical record review and full resequencing of the NAT2 coding region, we found no association of NAT2 coding alleles with sulfonamide hypersensitivity (predominantly cutaneous eruptions) in this adult Caucasian population.

Drug allergy: causes and desensitization

Allergic drug reactions occur when a drug, usually a low molecular weight molecule, has the ability to stimulate an immune response. This can be done in one of two ways. The first is by binding covalently to a self-protein, to produce a haptenated molecule that can be processed and presented to the adaptive immune system to induce an immune response. Sometimes the drug itself cannot do this but a reactive breakdown product of the drug is able to bind covalently to the requisite self-protein or peptide. The second way in which drugs can stimulate an immune response is by binding non-covalently to antigen presenting or antigen recognition molecules such as the major histocompatibility complex (MHC) or the T cell receptor. This is known as the p-I or pharmacological interaction hypothesis. The drug binding in this situation is reversible and stimulation of the response may occur on first exposure, not requiring previous sensitization. There is probably a dependence on the presence of certain MHC alleles and T cell receptor structures for this type of reaction to occur.

Safety of saxagliptin: rationale for and design of a series of postmarketing observational studies

PURPOSE

To describe the design and rationale of a series of postmarketing studies to examine the safety of saxagliptin, an oral dipeptidyl peptidase-4 inhibitor for the treatment of type 2 diabetes mellitus, in real-world settings.

METHODS

We are conducting a series of retrospective cohort studies using two UK (General Practice Research Database, and The Health Improvement Network) and two US (Medicare, HealthCore Integrated Research Database(SM) ) data sources. The primary outcomes of interest will include (i) hospitalization with acute liver failure, (ii) hospitalization for acute kidney injury, (iii) hospitalization for severe hypersensitivity reactions, (iv) hospitalization for severe infections, (v) hospitalization with infections associated with T-lymphocyte dysfunction (i.e., herpes zoster, tuberculosis, or nontuberculous mycobacteria), and (vi) major cardiovascular events. Diagnosis codes for the outcomes of interest will be validated by medical record review within each data source. Projected use and estimated incidence rates of outcomes of interest suggest there will be at least 80% statistical power to detect a minimum hazard ratio of 1.5 for major cardiovascular events, 2.0 for acute kidney injury and severe infections, 2.4 for acute liver failure, and 4.0 for severe hypersensitivity reactions.

RESULTS

Forthcoming.

CONCLUSIONS

This postmarketing safety assessment will provide important information regarding the safety of saxagliptin and could potentially identify important dipeptidyl peptidase-4 inhibitor class effects. The methods described may be useful to others planning similar evaluations.

Oral acetazolamide after Boston keratoprosthesis in Stevens-Johnson syndrome

Background

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a rare but severe and sometimes fatal condition associated with exposure to medications; sulfamethoxazole is among the most common causes. We sought to address the safety of acetazolamide, a chemically related compound, in patients with prior SJS/TEN and glaucoma. A retrospective case series is described of patients at the Massachusetts Eye and Ear Infirmary who underwent keratoprosthesis surgery for corneal blindness from SJS/TEN, and later required oral acetazolamide for elevated intraocular pressure.

Findings

Over the last 10 years, 17 patients with SJS/TEN received a Boston keratoprosthesis. Of these, 11 developed elevated intraocular pressure that required administration of oral acetazolamide. One of 11 developed a mild allergic reaction, but no patient experienced a recurrence of SJS/TEN or any severe adverse reaction.

Conclusion

Although an increase in the rate of recurrent SJS/TEN due to oral acetazolamide would not necessarily be apparent after treating only 11 patients, in our series, acetazolamide administration was well tolerated without serious sequela.

[Does hypersensitivity to multiple drugs really exist?]

BACKGROUND

Multiple-drug hypersensitivity (MDH) in the literature concerns different entities. Our objective was to define its frequency and characteristics in patients examined for cutaneous adverse drug reaction (CADR) before studying genetic predisposition.

MATERIALS AND METHODS

From a database comprising all patients referred for CADR between 2000 and 2010, we selected those meeting the following criteria: sensitisation to at least two chemically unrelated substances, as confirmed by positive skin tests or challenge tests. The following were excluded: patients with haematological diseases, HIV or chronic wounds and sensitization to the excipients.

RESULTS

Of the 1925 patients included, 11 (0.6%) were classed as polysensitized: eight women and three men, of mean age 62 years, presenting 2.5 episodes of drug hypersensitivity per patient. Four cases of DRESS were noted.

DISCUSSION

The strict criteria stipulated for this study enabled us to select patients with MDH, and to affirm that while it does in fact exist, it seems rare. Compared to polysensitized patients described in the literature, we preferred to distinguish between three groups of MDH: one occurring with different substances in separate episodes of CADR, one occurring with different substances during the same episode of CADR, and one occurring during DRESS and correlating with viral replication.

CONCLUSION

MDH exists and genetic predisposition could be investigated by studying cytokine polymorphism in such patients. However, because of its rarity, it is impossible to rule out fortuitous association of two episodes of CADR in the same patient.

Revisiting "older" antimicrobials in the era of multidrug resistance

Infections due to multidrug-resistant (MDR) organisms continue to increase, and the antimicrobial pipeline remains unacceptably lean. Given this challenge, it is has become necessary to use older antimicrobials for treatment of MDR pathogens despite concerns regarding toxicity and the lack of clinical efficacy data. In some cases, older antimicrobials offer potential advantages compared with new agents, including lower cost and better in vitro activity. In this review, we focus on the pharmacology, in vitro activity, and clinical experience of older agents, including colistin, minocycline, trimethoprim-sulfamethoxazole, and fosfomycin. We also discuss some new antimicrobial agents that are used to treat MDR pathogens. As MDR pathogens continue to outpace the development of new antimicrobials, it will become imperative to develop strategies regarding the optimal use of older agents in terms of monotherapy versus combination therapy, dosing regimens, and treatment of invasive infections caused by these pathogens.

Use of acetazolamide in sulfonamide-allergic patients with neurologic channelopathies

OBJECTIVE

To report the safe and successful use of the carbonic anhydrase inhibitor acetazolamide for treatment of patients with episodic ataxia and periodic paralysis who had been denied treatment because of a history of severe allergic reactions to antibiotic sulfonamides.

DESIGN

Case reports.

SETTING

University of Rochester Medical Center, Rochester, New York.

PATIENTS

A 61-year-old man with late-onset episodic ataxia, an 83-year-old woman with mutation-positive Andersen-Tawil syndrome, and a 21-year-old woman with mutation-positive episodic ataxia 2, all of whom had a history of severe skin rash with the use of sulfonamides for treatment of infection.

RESULTS

The 3 patients had been considered for carbonic anhydrase inhibitor treatment but a pharmacist had refused to fill a prescription for acetazolamide for 1 patient and the other 2 patients were denied treatment because of the allergy history. All 3 patients were prescribed acetazolamide and had no adverse reaction. Two patients improved substantially and are continuing treatment. A review of the pharmacology literature suggests that cross-reactivity between antibiotic and nonantibiotic carbonic anhydrase inhibitors is unlikely. Moreover, a review of case reports does not suggest cross-reactivity. Previous reports in the ophthalmology literature also indicate that acetazolamide can be administered to patients with a history of antibiotic sulfonamide allergic reaction.

CONCLUSIONS

These 3 cases confirm that the carbonic anhydrase inhibitor acetazolamide can be given to patients with a history of allergic skin rash with antibiotic sulfonamide.

Drug allergy

Drug allergy encompasses a spectrum of immunologically-mediated hypersensitivity reactions with varying mechanisms and clinical presentations. This type of adverse drug reaction (ADR) not only affects patient quality of life, but may also lead to delayed treatment, unnecessary investigations, and even mortality. Given the myriad of symptoms associated with the condition, diagnosis is often challenging. Therefore, referral to an allergist experienced in the identification, diagnosis and management of drug allergy is recommended if a drug-induced allergic reaction is suspected. Diagnosis relies on a careful history and physical examination. In some instances, skin testing, graded challenges and induction of drug tolerance procedures may be required.

The most effective strategy for the management of drug allergy is avoidance or discontinuation of the offending drug. When available, alternative medications with unrelated chemical structures should be substituted. Cross-reactivity among drugs should be taken into consideration when choosing alternative agents. Additional therapy for drug hypersensitivity reactions is largely supportive and may include topical corticosteroids, oral antihistamines and, in severe cases, systemic corticosteroids. In the event of anaphylaxis, the treatment of choice is injectable epinephrine. If a particular drug to which the patient is allergic is indicated and there is no suitable alternative, induction of drug tolerance procedures may be considered to induce temporary tolerance to the drug.

This article provides a backgrounder on drug allergy and strategies for the diagnosis and management of some of the most common drug-induced allergic reactions, such allergies to penicillin, sulfonamides, cephalosporins, radiocontrast media, local anesthetics, general anesthetics, acetylsalicylic acid (ASA) and non-steroidal anti-inflammatory drugs.

Immune reactions to drugs and diagnostic agents

Adverse reactions to drugs are common, but only a small percentage of these reactions results from a specific immune reaction to a drug. Over-reactivity of almost any part of the immune system can result in an immunologically mediated drug reaction; however, T cell-and immunoglobulin E-mediated reactions are the most common. The reactions are unpredictable and can involve any part of the body, although skin is most frequent. The various pathogenic mechanisms are discussed, along with diagnostic testing, factors predisposing to drug allergy, and reactions to individual drugs and therapeutic reagents.

Patch testing in fixed drug eruptions--a 20-year review

BACKGROUND

The fixed drug eruption is a common adverse drug reaction. Clear identification of the culprit drug is not always possible in the clinical setting, and oral rechallenge may induce new lesions or severe reactions.

OBJECTIVES

The main purpose of this study was to evaluate the diagnostic value of patch testing in establishing an aetiological diagnosis in fixed drug eruptions.

METHOD

A retrospective analysis was conducted evaluating 52 patients (17M/35F, mean age 53±17 years) with clinical diagnoses of fixed drug eruptions submitted to patch tests in a 20-year period in a Dermatology Department. Nonsteroidal anti-inflammatory drugs (NSAID) were clinically suspected in 90.4% of the cases, followed by antibiotics (28.9%) and paracetamol (15.4%).

RESULTS

Patch tests on pigmented lesions were reactive in 21 patients (40.4%), 20 of those to NSAID (nimesulide, piroxicam and etoricoxib) and 1 to an antihistamine (cetirizine). All patch tests using other drugs were negative, even under conditions of high clinical suspicion. Oral rechallenge allowed confirmation of drug imputability in 5 of 31 test-negative cases. Cross reactivity was frequently observed between piroxicam and other oxicams, and between different antihistamines.

CONCLUSIONS

Patch testing was shown to be a simple and safe method to confirm drug imputabililty in fixed drug eruption, mainly when NSAID or multiple drugs are suspected. Persistent lack of reactivity to drug classes such as antibiotics and allopurinol represent an important limitation.

Four nephrology myths debunked

There are many controversial topics relating to renal disease in hospitalized patients. The aim of this review is to shed light on some important and often debated issues. Hypothyroidism, unlike myxedema, is not a cause of hyponatremia (although it can be sometimes seen in conjunction with the latter) and additional investigations should be done to determine its etiology. Sodium bicarbonate is effective for treatment of hyperkalemia primarily by enhancing renal potassium elimination rather than by translocating potassium into cells. Acetaminophen can be a cause of metabolic acidosis by causing 5-oxoprolinuria. Furosemide (and sulfa containing diuretics) can safely be used in patients with an allergy to sulfa-containing antibiotics (SCA).

Acetazolamide and sulfonamide allergy: a not so simple story

Allergies and adverse reactions to sulfonamide medications are quite common. Two distinct categories of drugs are classified as sulfonamides: antibiotics and nonantibiotics. The two groups differ in their chemical structure, use, and the rate at which adverse reactions occur. Cross-reactivity between the two groups has been implied in the past, but is suspect. Acetazolamide, from the nonantibiotic group, is routinely used in the prevention and treatment of high altitude issues and may not need to be avoided in individuals with a history of sulfonamide allergy. This review addresses the differences between the groups and the propensity for intergroup and intragroup adverse reactions based on the available literature. We also examine the different clinical presentations of allergy and adverse reactions, from simple cutaneous reactions with no sequelae through Stevens-Johnson syndrome and anaphylaxis, with risk for significant morbidity and mortality. We offer a systematic approach to determine whether acetazolamide is a safe option for those with a history of allergy to sulfonamides.

Drug allergy: an updated practice parameter

Adverse drug reactions (ADRs) result in major health problems in the United States in both the inpatient and outpatient setting. ADRs are broadly categorized into predictable (type A and unpredictable (type B) reactions. Predictable reactions are usually dose dependent, are related to the known pharmacologic actions of the drug, and occur in otherwise healthy individuals, They are estimated to comprise approximately 80% of all ADRs. Unpredictable are generally dose independent, are unrelated to the pharmacologic actions of the drug, and occur only in susceptible individuals. Unpredictable reactions are subdivided into drug intolerance, drug idiosyncrasy, drug allergy, and pseudoallergic reactions. Both type A and B reactions may be influenced by genetic predisposition of the patient

High-altitude illnesses: physiology, risk factors, prevention, and treatment

High-altitude illnesses encompass the pulmonary and cerebral syndromes that occur in non-acclimatized individuals after rapid ascent to high altitude. The most common syndrome is acute mountain sickness (AMS) which usually begins within a few hours of ascent and typically consists of headache variably accompanied by loss of appetite, nausea, vomiting, disturbed sleep, fatigue, and dizziness. With millions of travelers journeying to high altitudes every year and sleeping above 2,500 m, acute mountain sickness is a wide-spread clinical condition. Risk factors include home elevation, maximum altitude, sleeping altitude, rate of ascent, latitude, age, gender, physical condition, intensity of exercise, pre-acclimatization, genetic make-up, and pre-existing diseases. At higher altitudes, sleep disturbances may become more profound, mental performance is impaired, and weight loss may occur. If ascent is rapid, acetazolamide can reduce the risk of developing AMS, although a number of high-altitude travelers taking acetazolamide will still develop symptoms. Ibuprofen can be effective for headache. Symptoms can be rapidly relieved by descent, and descent is mandatory, if at all possible, for the management of the potentially fatal syndromes of high-altitude pulmonary and cerebral edema. The purpose of this review is to combine a discussion of specific risk factors, prevention, and treatment options with a summary of the basic physiologic responses to the hypoxia of altitude to provide a context for managing high-altitude illnesses and advising the non-acclimatized high-altitude traveler.

Practical management of antibiotic allergy in adults

This review looks at the main issues around immediate hypersensitivity and the role and limitations of testing. The majority of literature on antibiotic hypersensitivity relates to β-lactam antibiotics, mainly because of the heavy usage of this class of drugs. Concerns around cross-reactivity always worry clinicians, particularly in the emergency situation. Reasonable data now exist in relation to β-lactam antibiotics and derivatives, which enable appropriate risk management to be undertaken. The available literature for other classes of antibiotics is also discussed.

Approach to the patient with drug allergy

Clinicians commonly encounter patients who report to have drug allergy. In a large part, such allergy corresponds to adverse drug reactions, which are not immune mediated. The incriminated drug need not always be avoided for further therapy. On the other hand, drug allergy may manifest in many unexpected clinical pictures and thus not be recognized. There is no single standardized diagnostic test to confirm the immune-mediated mechanism and to identify the causative drug. Therefore, immune-mediated drug hypersensitivity reactions and their causative drugs have to be considered by the constellation of exposure, timing, and clinical features, including the pattern of organ manifestation. Prior experience with the drug is also an important feature. An allergologic workup with additional investigation may provide some help. Patients should be informed carefully about their drug allergy, whereby symptoms, drug that elicits reaction, modes of diagnosis of drug allergy, and possibly alternatives should be indicated in their allergy passport.

Stevens-Johnson syndrome associated with furosemide: a case report

PURPOSE

To report a probable association of Stevens-Johnson Syndrome (SJS) with furosemide and suspected cross-sensitivity with lincomycin and silver sulfadiazine cream.

SUMMARY

A 28-year-old Hispanic male was admitted for SJS, with a prolonged hospital course and unclear etiology throughout the majority of the stay. Patient's medications prior to development of SJS symptoms were stable for 3 months and with the exception of furosemide, all were continued throughout the hospitalization while the SJS resolved. During hospitalization, the patient was unintentionally rechallenged with furosemide, after which the rash reappeared and then worsened further with use of silver sulfadiazine cream. At this point in the hospitalization, the prolonged course of the rash prior to admission and the administration of lincomycin 3 days prior to admission were revealed. This suggests the SJS was initially caused by furosemide, a nonaromatic sulfonamide diuretic, with slow progression prior to hospital admission over approximately 7 weeks, followed by an acute worsening caused by lincomycin, a sulfide antibiotic.

CONCLUSION

Use of the Naranjo ADR Probability Scale indicates a probable relationship between SJS and furosemide in this patient. Clinicians should be aware of this rare potential adverse effect, even months after the initiation of therapy.

Knowledge and attitudes of American pharmacists concerning sulfonamide allergy cross-reactivity

OBJECTIVE

Pharmacists are commonly confronted with patients with a history of sulfonamide allergy. Basic immunologic and clinical data suggest a low likelihood of a patient with a history of sulfonamide hypersensitivity developing an allergic reaction to a non-antimicrobial sulfonamide drug. We conducted a survey to describe the knowledge and attitudes of licensed pharmacists concerning sulfonamide allergy cross-reactivity.

METHODS

A survey instrument was developed and sent to all licensed pharmacists in the state of Iowa. The survey recorded demographic information and included six patient scenarios designed to elicit responses concerning sulfonamide allergy cross-reactivity with a number of non-antimicrobial sulfonamides.

RESULTS

A total of 421 surveys were returned for a 39% response rate. There was a wide discrepancy in approaches to patients with a history of sulfonamide allergy prescribed a sulfonamide containing non-antibiotic. Differences depended on previous history of tolerating the medication in question, the degree of cautionary statements in product literature, and the familiarity the pharmacist had with the product.

CONCLUSION

Our survey suggests a significant diversity in knowledge and attitudes of pharmacists concerning cross-reactivity of sulfonamide antimicrobials and other drugs with a sulfonamide moiety. Depth of training in this area may be an associative factor.

Management of loop diuretic resistance in the intensive care unit

PURPOSE

The management of loop diuretic resistance in the intensive care unit (ICU) is reviewed.

SUMMARY

Volume overload, a common complication of fluid resuscitation, is frequently encountered in the ICU and is associated with numerous adverse effects, including pulmonary and peripheral edema, acute lung injury, and pleural effusions. Loop diuretics are used to treat volume overload and acute renal failure and to ameliorate their associated complications. When administered intravenously, these drugs induce vigorous and prompt diuresis, which may result in negative fluid balance. This may also result in significant adverse effects, including electrolyte imbalance, ototoxicity, and volume contraction. Prolonged use of loop diuretics may lead to loop diuretic resistance, a frequent observation in the ICU. Three general mechanisms are used to explain loop diuretic resistance: rebound sodium retention, postdiuretic effect, and diuretic braking. While very few agents have joined the armamentarium and no new strategies have been developed to deal with this phenomenon, several options are available to clinicians for managing loop diuretic resistance, including salt restriction, administration of i.v. loop diuretics, continuous infusion of loop diuretics, and combination therapy using loop diuretics and thiazides.

CONCLUSION

Loop diuretic resistance presents a challenge for clinicians in the ICU setting. Strategies to improve patients' responsiveness to these agents include fluid and salt restriction, switching from oral to i.v. loop diuretics, increasing diuretic dose, continuous infusion, and combination therapy with thiazides. Several of these strategies may be used concurrently to combat diuretic resistance and promote symptomatic relief of edema in the critically ill patient.

Approach to the patient with drug allergy

Drug allergies are adverse drug reactions mediated by the specific immune system. Despite characteristic signs (eg, skin rash) that raise awareness for possible drug allergies, they are great imitators of disease and may hide behind unexpected symptoms. No single standardized diagnostic test can confirm the immune-mediated mechanism or identify the causative drug; therefore, immune-mediated drug hypersensitivity reactions and their causative drugs must be recognized by the constellation of exposure, timing, and clinical features including the pattern of organ manifestation. Additional allergologic investigations (skin tests, in vitro tests, provocation tests) may provide help in identifying the possible eliciting drug.

Vancomycin-induced leukocytoclastic vasculitis

Vancomycin is well recognized as causing the nonallergic skin reaction known as red man syndrome; however, it is rarely suspected as causative in the setting of an immune-mediated skin reaction. We describe a 76-year-old Caucasian woman with a history of penicillin and sulfa allergies who was transferred to our medical center while receiving vancomycin for treatment of persistent methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia. After admission, the patient's pacemaker was explanted; cultures from the pacemaker grew MSSA. Based on the culture data and her allergy to penicillin, vancomycin was continued. On day 4 of therapy, the patient developed a papular rash with small blisters on her distal upper extremities. Furosemide, which she was receiving intermittently to maintain fluid balance, was initially suspected as the likely cause. Furosemide was withheld; however, the rash worsened and spread to her neck and torso. Results of skin biopsy confirmed a severe leukocytoclastic, necrotizing small-cell vasculitis that met the criteria for a hypersensitivity vasculitis associated with drug therapy. Five days after discontinuation of vancomycin, the vasculitis was resolving and continued to resolve throughout the remainder of her hospitalization. Furosemide was readministered without worsening of the vasculitis. Use of the Naranjo adverse drug reaction probability scale indicated that the likelihood of vancomycin being the cause of the vasculitis was probable (score of 5). Clinicians should be aware of vancomycin as a potential cause of small-vessel vasculitis.

Self-reported antibiotic allergy incidence and prevalence: age and sex effects

BACKGROUND

Data on the prevalence and incidence of adverse reactions to antibiotics in outpatient populations are rare. These events are commonly called "allergy" when noted in the medical record.

OBJECTIVES

Determine the prevalence and incidence of allergy, as recorded in the medical record, to the most commonly used antibiotic classes in a large outpatient population using health care in the United States during 2007.

METHODS

Data for drug allergy and antibiotic use were extracted from the electronic health records of 411,543 patients cared for by Kaiser Permanente in San Diego County who had at least one outpatient visit during 2007. Outpatient antibiotic utilization data was obtained for each year between 1995 and 2007. Penicillins, sulfas, cephalosporins, tetracyclines, macrolides, and quinolones were the classes of antibiotics evaluated.

RESULTS

Antibiotics account for a majority of drug allergy entries. Antibiotic classes with higher historical use have higher allergy prevalence. Female patients use more antibiotics than males, and have higher allergy prevalence rates for all classes of antibiotics. There is a steady increase in antibiotic allergy prevalence with aging for both sexes. Females have higher allergy incidence rates for all classes of antibiotics. Antibiotic allergy incidence in female patients is highest for sulfas, 3.4%, compared with 1%-1.5% for all other classes of antibiotics. Antibiotic allergy incidence in males also is highest for sulfas, 2.2%, compared with 1.1% for penicillins and 0.5%-0.6% for all other classes of antibiotics.

CONCLUSIONS

Female sex, use, and increasing age are the primary factors that account for higher antibiotic allergy prevalence. Antibiotic allergy incidence is highest with sulfa class antibiotics.

Prescribing errors in patients with documented drug allergies: comparison of ICD-10 coding and written patient notes

INTRODUCTION

Allergies to drugs are a major cause for hospitalisation and inappropriate prescriptions to patients. However, allergies can be prevented if the patient's history of drug allergy is known and coded.

OBJECTIVE OF THE STUDY

Assessment of the value of the widely used ICD-10 codes for drug-allergies (e.g. Z88, L27) as triggers for decision support in an electronic prescription system and evaluation of the potential impact of such an alert system. We also evaluated the usefulness of manual drug allergy notes recorded in patients' charts in the prevention of prescribing errors due to drug allergies.

SETTING

University hospital providing primary and tertiary care.

METHODS

Using Anatomical Therapeutic Chemical (ATC) classification codes we allocated to drug specifying ICD-10 codes (i.e. Z88) all drugs belonging to the same group of compounds or those known to induce cross-allergy. In a randomly selected cohort of 200 in-patients we then assessed documentation and coding of drug allergies and incident prescribing errors ignoring patients' drug allergies.

RESULTS

Eighteen of the 200 patients had an allergy-related ICD code in the chart, 51 had a written note, and 13 had both. About 21% of patients with documented drug allergies were prescribed a drug potentially triggering the allergy. There was no difference in prescribing errors due to drugs potentially inducing allergies when the allergy was only documented as an ICD-10 code or the information was available in the paper record (P > 0.05).

CONCLUSION

The findings of this study emphasise the necessity of a more precise and efficient documentation system of drug allergies along with the implementation of an electronic CDS for drug allergies that makes physicians aware of patients' drug allergies during the prescribing process.

Severe allergic reaction to hydrochlorothiazide mimicking septic shock

Hydrochlorothiazide (HCTZ) is a sulfonamide-containing drug with commonly reported adverse effects that include electrolyte abnormalities, orthostatic hypotension, hyperglycemia, and photosensitivity. A few reports have described rare but serious drug complications such as interstitial pneumonitis, angioedema, and aplastic anemia. We describe a patient who experienced a serious HCTZ-induced adverse event that, to our knowledge, has not yet been reported in the literature. A 78-year-old woman came to the emergency department with dyspnea and severe fatigue; her signs and symptoms were suggestive of septic shock from pneumonia. She was treated accordingly, her condition improved, and she was discharged home. During the next 2 months, the patient returned to the emergency department 2 more times and was hospitalized each time with the same diagnosis. During her third admission, it was discovered that the patient's primary care physician had restarted her HCTZ for hypertension after it had been discontinued during each of the first two hospitalizations. The patient's symptoms began within hours of the first and second hospitalizations and almost immediately after taking a dose of HCTZ on the day of the third hospitalization. Her medical history revealed documented allergic reactions to sulfonamide drugs and penicillin; thus a hypersensitivity reaction to HCTZ was suspected. Use of the Naranjo adverse drug reaction probability scale indicated a probable relationship between the patient's hypersensitivity reactions and HCTZ therapy. Because of a lack of evidence showing cross-reactivity among the different classes of sulfonamides, the mechanism of the allergic reaction to HCTZ was unlikely to be cross-sensitivity between sulfonamide antibiotics and sulfonamide nonantibiotic drugs. Although the mechanism is not clear, evidence shows that the allergy to the HCTZ (sulfonamide nonantibiotic) may be due to a predisposition to drug allergies rather than sulfonamide cross-sensitivity. Clinicians should be aware of the potential for these types of allergic reactions.

Celecoxib-associated anaphylaxis

OBJECTIVE

To report and discuss a case of anaphylaxis in a young, healthy white male taking celecoxib for intermittent lower back pain.

CASE SUMMARY

A healthy 27-year-old man with a documented history of anaphylaxis to penicillins and macrolides presented to the emergency department (ED) in anaphylactic shock after ingesting a 200-mg capsule of celecoxib and a cup of orange juice. The patient had been taking celecoxib over the past 6 months, for 1-2 weeks at a time, for low back pain secondary to a pilonidal cyst and an L5/S1 bulging disc. The day of admission was the seventh day of the most recent course of twice-daily celecoxib. The patient initially self-treated the reaction with diphenhydramine and subcutaneous epinephrine that he had at home due to his history of drug- and bee sting-induced anaphylaxis; neither intervention improved his symptoms. He became profoundly diaphoretic and developed systemic swelling, shortness of breath, bradycardia, and hypotension. Emergency medical services transported the patient to the ED, where he was treated appropriately and the symptoms resolved. However, 4 hours later, at time of discharge from the ED, the symptoms recurred. He was admitted to the intensive care unit and monitored for 3 days. Supportive care, steroids, and histamine blockade provided resolution of the symptoms. Cardiac workup was initiated because of the recurrence and severity of bradycardia and hypotension; results of the workup were unremarkable. The patient was discharged in stable condition.

DISCUSSION

This case demonstrates rare anaphylaxis to celecoxib in a patient who had previously taken the drug and who had documented tolerance to sulfonamide antibiotics. Despite this history, our patient developed type V immunoglobulin E-mediated anaphylaxis secondary to the sulfonamide component of celecoxib. This reaction was considered probable according to the Naranjo probability scale. A review of published case reports and related allergy literature for celecoxib allergenicity revealed that such reactions are rare. This is the first case report with great detail of a patient with anaphylaxis to celecoxib after having previously tolerated the medication.

CONCLUSIONS

Celecoxib can produce an anaphylactic reaction in patients who have previously tolerated sulfonamide antibiotics and who have previously tolerated celecoxib. This case also reviews the potentially biphasic presentation of anaphylaxis. Clinicians need to be aware of this biphasic anaphylactic response to ensure optimal duration of evaluation.

A Review of Critical Differences among Loop, Thiazide, and Thiazide-Like Diuretics

Diuretics are a drug class with heterogeneous assortments. This article reviews general pharmacologic mechanisms and clinical implications of loop, thiazide, and thiazide-like diuretics.

Loop diuretics act in the loop of Henle by blocking the sodium-potassium-chloride (Na+-K+-2Cl-) symport. They are effective in relieving congestive symptoms and edematous signs of heart failure. Activation of the neurohormonal system and subsequent pathologic myocardial remodeling limit the use of loop diuretics unless fluid balance is not met to relieve patients' symptoms with life-saving pharmacologic modalities. Adverse effects on electrolyte balance may cause life-threatening consequences. The combination of K+-sparing diuretics or angiotensin-converting enzyme inhibitors with loop diuretics may not only prevent life-threatening complications caused by electrolyte imbalance, but also may delay progression of the disease with proven mortality benefit. Recent findings of worsening renal function and higher mortality rate with the use of oral and intravenous loop diuretics further demands appropriate use of these drugs.

Thiazide diuretics and thiazide-like diuretics act in the distal convoluted tubule by blocking Na+-Cl- symport. Thiazide diuretics reduce cardiovascular mortality by achieving target blood pressure in patients with hypertension. Compared with other antihypertensive drugs, thiazide diuretics have less desirable metabolic effects. However, it has not yet been shown that the negative metabolic effects of these drugs are associated with negative mortality and morbidity. Based on the need for a multidrug regimen to reach target blood pressure in most patients with hypertension, thiazide diuretics may be used in addition to a drug or drugs without metabolic complications.

Antibiotic allergies in the medical record: effect on drug selection and assessment of validity

STUDY OBJECTIVES

To determine the frequency with which reported antibiotic allergies alter drug selection and to assess the validity of these allergies.

DESIGN

Retrospective medical record review, with concurrent interviews conducted in a selected subgroup of patients.

SETTING

Tertiary care academic medical center.

PATIENTS

Three hundred patients with at least one documented antibiotic allergy and who received an antibiotic while hospitalized.

MEASUREMENTS AND MAIN RESULTS

Data were collected to determine the patients' allergies documented in the medical record. The first antibiotic regimen that each patient received while hospitalized was evaluated for deviation from the standard of care as determined from institutional protocols, recommendations in the literature, and expert opinion. A total of 416 allergies to antibiotics were reported. Penicillins were the agents most commonly reported (198 reports), followed by sulfonamides, cephalosporins, macrolides, and fluoroquinolones. The reported allergies altered antibiotic therapy in 91 (30.3%) patients. Report of a penicillin or cephalosporin allergy and use of antibiotics for prophylaxis were strong predictors of altered therapy. The subgroup consisted of 100 patients who were interviewed to determine the specific details of their reported allergic reactions. For 22 of the 100 patients, major discrepancies were found between their verbal reports and medical record documentation. The Naranjo adverse drug reaction probability scale was used to determine the validity of their reactions. Among these 100 patients, 109 (78.4%) of 139 reported reactions to antibiotics were deemed to be allergic in nature. For 55 (50.5%) of the 109 allergic reactions, the Naranjo score was 5 or greater, which correlates with probable to definite validity.

CONCLUSION

Discrepancies between the medical record and in-depth allergy histories are common, and the validity of reported allergic reactions is frequently questionable. Because documentation of an antibiotic allergy frequently alters therapy, increased effort to verify these reactions may be beneficial.

Which medications are safe and effective for improving sleep at high altitude?

Given the well-established problems with sleep at high altitude, it is not uncommon for people planning trips to the mountains to seek advice from clinicians regarding pharmacologic options for improving sleep during their trip. This review article considers the various medications that have been studied for this purpose at high altitude with an emphasis on both their efficacy and safety. The available data support the use of either acetazolamide, temazepam, zolpidem or zaleplon in this environment. Other agents commonly used at sea-level such as eszopiclone and diphenhydramine have not been studied at high altitude but are likely safe to use given their mechanism of action and known side effects. Limited evidence suggests diazepam may cause hypoventilation at high altitude and its use in this environment should be discouraged. Insufficient data exist to determine which agent is most effective at altitude nor do we know whether combination therapy with acetazolamide and a hypnotic agent offers any benefits over monotherapy.