Hypersensitivity to trimethoprim

Antibiotic prophylaxis in immunosuppressed patients - Missed opportunities from trimethoprim-sulfamethoxazole allergy label

Trimethoprim-sulfamethoxazole (TMP-SMX) is a broad spectrum antibiotic in use for more than 50 years. It has an important indication as first line agent in the prophylaxis of opportunistic infections, particularly Pneumocystis jirovecii pneumonia (PJP), in immunosuppressed patients. For those who have a history of allergy or severe intolerance to TMP-SMX, pentamidine, dapsone or atovaquone may be substituted; however there is evidence that TMP-SMX offers superior coverage for PJP, toxoplasmosis, and nocardiosis. Compared to pentamidine, it has the added benefit of cost-effectiveness and self-administration as opposed to required hospital attendance for administration. Many patients who report a history of allergy or adverse reaction to TMP-SMX (or "sulfur allergy") will be found not to be allergic; and even those who are allergic may be able to be desensitized. The evaluation and, where appropriate, removal of TMP-SMX allergy label enables the use of TMP-SMX for prophylaxis against opportunistic infections. This is a cost-effective intervention to optimize antimicrobial prescribing and reduce the risk of opportunistic infections in immunosuppressed patients.

[Drug allergy: Fundamental aspects in diagnosis and treatment.]

BACKGROUND

Any substance used as a treatment for any disease can produce harmful or unpleasant events called adverse drug reactions (ADRs). They are due to inherent biological effects of the drug and are caused by immunological and non-immunological mechanisms.

OBJECTIVES

To describe the immunological mechanisms of hypersensitivity reactions (HSR) to drugs, their epidemiology, risk factors, classification, clinical manifestations, diagnosis, treatment, and prognosis.

METHODS

A review of the most current literature in English and Spanish was carried out, in the main databases, related to the HSR of various drug groups.

RESULTS

This study describes the terms used to define ADRs and HSRs, their classification and clinical manifestations, current diagnostic tools, treatment algorithms and prognosis of the most frequently used medications and with the highest prevalence of reported adverse events.

CONCLUSION

ADRs are a challenging entity, with a complex pathophysiology that has not been fully understood. Its approach requires a careful consideration since not all drugs have validated tests for their diagnosis nor a specific treatment. When indicating the use of any drug, the severity of the disease, the availability of other treatments and the potential risks of developing future adverse events should always be taken into consideration.

Whole genome sequencing identifies genetic variants associated with co-trimoxazole hypersensitivity in Asians

BACKGROUND

Co-trimoxazole, a sulfonamide antibiotic, is used to treat a variety of infections worldwide, and it remains a common first-line medicine for prophylaxis against Pneumocystis jiroveci pneumonia. However, it can cause severe cutaneous adverse reaction (SCAR), including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms. The pathomechanism of co-trimoxazole-induced SCAR remains unclear.

OBJECTIVE

We aimed to investigate the genetic predisposition of co-trimoxazole-induced SCAR.

METHODS

We conducted a multicountry case-control association study that included 151 patients with of co-trimoxazole-induced SCAR and 4631 population controls from Taiwan, Thailand, and Malaysia, as well as 138 tolerant controls from Taiwan. Whole-genome sequencing was performed for the patients and population controls from Taiwan; it further validated the results from Thailand and Malaysia.

RESULTS

The whole-genome sequencing study (43 case patients vs 507 controls) discovered that the single-nucleotide polymorphism rs41554616, which is located between the HLA-B and MICA loci, had the strongest association with co-trimoxazole-induced SCAR (P = 8.2 × 10^-9; odds ratio [OR] = 7.7). There were weak associations of variants in co-trimoxazole-related metabolizing enzymes (CYP2D6, GSTP1, GCLC, N-acetyltransferase [NAT2], and CYP2C8). A replication study using HLA genotyping revealed that HLA-B∗13:01 was strongly associated with co-trimoxazole-induced SCAR (the combined sample comprised 91 case patients vs 2545 controls [P = 7.2 × 10^-21; OR = 8.7]). A strong HLA association was also observed in the case patients from Thailand (P = 3.2 × 10^-5; OR = 3.6) and Malaysia (P = .002; OR = 12.8), respectively. A meta-analysis and phenotype stratification study further indicated a strong association between HLA-B∗13:01 and co-trimoxazole-induced drug reaction with eosinophilia and systemic symptoms (P = 4.2 × 10^-23; OR = 40.1).

CONCLUSION

This study identified HLA-B∗13:01 as an important genetic factor associated with co-trimoxazole-induced SCAR in Asians.

Efficacy and safety of quinolones for the treatment of uncomplicated urinary tract infections in women: a network meta-analysis

INTRODUCTION AND HYPOTHESIS

Uncomplicated urinary tract infection (uUTI) is defined as the presence of pathogenic organisms in the urinary tract without anatomical and functional abnormalities, is accompanied by inflammatory leukocytes and cytokines and may or may not develop clinical symptoms. The frequency of uncomplicated urinary tract infection is higher in young women. Several quinolone treatment regimens are available; however, since we do not know which is the best antibiotic regimen for the treatment of this urinary infection, we analyzed the published evidence and conducted a systematic review with network meta-analysis. The aim was to compare and hierarchize quinolones according to their efficacy and safety and to identify the best treatment for uncomplicated urinary tract infection in women through a systematic review with network meta-analysis.

METHODS

Medline, Embase, LILACS, Cochrane CENTRAL and other databases were searched for trials. Bias in the trials was assessed using the Cochrane Collaboration tool. To analyze efficacy and adverse events, for direct comparisons, we obtained risk ratios and 95% confidence intervals by applying a fixed-effects model using tau² and Q² tests to calculate the heterogeneity. For the network meta-analysis, we analyzed the indirect comparisons by Bucher's method.

RESULTS

We included 18 trials (8765 women). For premenopausal women, ofloxacin had a 57% probability of achieving remission but an 83% frequency of adverse events. For postmenopausal women, ofloxacin was 82% more effective for remission, with a 49% frequency of adverse events, compared with other types of quinolones.

CONCLUSIONS

Compared with other quinolones, ofloxacin 200 mg once daily for a treatment duration < 3 days provides the highest clinical and bacteriological remission rates with the lowest relapse and resistance rates for the treatment of women with uUTIs. However, additional trials are needed to confirm our findings, especially when the treatment duration exceeds 3 days.

Anaphylaxis to trimethoprim: An under-appreciated risk in acute medical care

Anaphylaxis is a severe, systemic allergic reaction, which is frequently unexpected and carries a high mortality risk as a medical emergency. Anaphylaxis to trimethoprim is not a well recognized event. Since trimethoprim represents the leading antibiotic for the treatment of urinary tract infections, its potential to cause anaphylaxis needs to be recognized, whether alone or as the 'active' ingredient in cotrimoxazole (trimethoprim-sulphamethoxazole combination), by those prescribing it and those providing acute care. A case of probable anaphylaxis following trimethoprim ingestion is presented with discussion supporting its potency including evidence at an immunological level highlighting its under-appreciated risk in acute medical care.

Recognising antibacterial hypersensitivity in children

Adverse reactions to antibacterial agents are not uncommon in children. They are classified as 'immediate' or 'nonimmediate' according to the time interval between drug administration and onset. Immediate reactions occur within 1 hour and are manifested by urticaria and/or angioedema, bronchospasm and anaphylactic shock; immunological reactions are mediated by IgE antibodies. The main nonimmediate reactions (occuring after more than 1 hour) are maculopapular rash, urticaria and serum sickness; T lymphocytes may participate in maculopapular rash. Clinical assessment of such reactions is complex. The patient's history is fundamental; the allergological examination includes in vivo and in vitro tests selected on the basis of the clinical features and the phase of reaction. In the late phase, prick and intradermal tests are sensitive in evaluating beta-lactam allergy. Together with delayed-reading intradermal testing, patch testing seems to be useful in diagnosing maculopapular reactions to systemically administered aminopenicillins. Determination of specific IgE levels is the most common in vitro method for diagnosing immediate reactions. In the acute phase, serum tryptase and urinary N-methylhistamine assays are reliable in diagnosing type I pathogenic mechanisms in immediate reactions. Unfortunately, there are few in vitro tests for evaluating other reactions, and most are not fully validated. In selected cases, provocation tests should be performed.

Anaphylactic reactions associated with trimethoprim

BACKGROUND

Anaphylactic reactions to cotrimoxazole are often ascribed to the sulphamethoxazole component of this antibacterial drug.

OBJECTIVE

To determine whether the trimethoprim component can be the cause of an anaphylactic reaction.

METHODS

An analysis was made of reports on anaphylaxis attributed to trimethoprim, as notified to the Drug Safety Unit of the Dutch Inspectorate for Health Care.

RESULTS

In the period between September 1981 and November 1995, 13 such reports were received. Nine were classified as probable anaphylaxis. Of these, the causal relationship between exposure to trimethoprim and anaphylaxis was classified as definite in three reports, and as probable in the other six. The remaining four reports were classified as possible anaphylaxis. In one of these, the causal relationship was classified as definite, and in three as probable.

CONCLUSION

Although anaphylaxis due to trimethoprim seems to be rare, it may be more common than previously thought. Apparently, anaphylaxis to cotrimoxazole is not always caused by sulphamethoxazole.