Trimethoprim/sulfamethoxazole desensitization

Successful outpatient graded administration of trimethoprim-sulfamethoxazole in patients without HIV and with a history of sulfonamide adverse drug reaction

BACKGROUND

The outcomes of trimethoprim-sulfamethoxazole (TMP-SMX) desensitization have been widely reported in the HIV literature but less so in the non-HIV literature.

OBJECTIVE

To evaluate the safety and efficacy of graded administration of TMP-SMX in patients without HIV and with a history of TMP-SMX adverse drug reaction (ADR).

METHODS

A retrospective chart review, 2004-2012, of all the patients without HIV seen in the Division of Allergic Diseases and with a history of TMP-SMX ADR who underwent outpatient graded administration of TMP-SMX was conducted. The medical record was reviewed for age, sex, details of the initial ADR to TMP-SMX, an indication for TMP-SMX administration, and outcome. Patients also were contacted by telephone, and medical records were reviewed to determine long-term outcomes.

RESULTS

Seventy-two patients (46 women [64%]; mean [SD] age, 57.7 ± 13.89 years]) were included. The most common patient-reported reactions to TMP-SMX were rash 39 (54%), and hives 9 (13%). TMP-SMX administration was needed for the following indications: prophylaxis (62 [86%]) and treatment of infection (10 [14%]). Forty-three of the patients (60%) underwent a 1-day TMP-SMX administration protocol. Thirty-five of the 43 (81%) underwent a 6-step (90 minutes to 6 hours) protocol and 7 of the 43 (16%) underwent a novel 14-step TMP-SMX protocol. Twenty-nine (40%) underwent a >1-day TMP-SMX administration protocol. Our overall success rate was 90% (mean duration of 11 months). Ninety-eight percent of the patients successfully completed a 1-day graded administration protocol, and 76% successfully completed a >1-day protocol. TMP-SMX was stopped in 8 patients because of the ADR.

CONCLUSION

We report the largest case series of successful outpatient graded administration of TMP-SMX with both 1-day and >1-day protocols, which have shown to be safe and well tolerated in patients without HIV and with a history of sulfonamide ADR.

Anaphylaxis: past, present and future

Anaphylaxis is a clinical emergency, and recent reports suggest increased prevalence. A diverse set of primary genetic and environmental influences may confer susceptibility to anaphylactic reactions. Anaphylaxis presents diagnostic and therapeutic challenges. It often manifests with a broad array of symptoms and signs that might be similar to other diseases. The management of anaphylaxis consists of emergency treatment of acute episodes as well as preventive strategies to avoid recurrences. Treatment is complicated by its rapid onset and progression, presence of concurrent diseases or medications, and need for long-term allergen avoidance. Health care professionals must be able to recognize the signs of anaphylaxis, treat an episode promptly and appropriately, and provide preventive recommendations. Recognizing the gaps in our understanding and management of anaphylaxis may help identify promising targets for future treatment and prevention and areas that require further study.

Intravenous Linezolid Administered Orally: A Novel Desensitization Strategy

A 41-year-old woman with a history of myasthenia gravis was admitted to a local hospital because of severe muscle weakness, ptosis, shortness of breath, nausea and vomiting, and fever. Blood cultures revealed Enterococcus faecium resistant to several antimicrobial agents. The organism had minimum inhibitory concentrations above 16 microg/ml for vancomycin and above 2 microg/ml for quinupristin-dalfopristin. In the absence of therapeutic alternatives, treatment with linezolid was required (minimum inhibitory concentration 1.5 microg/ml). The first dose of linezolid resulted in a hypersensitivity reaction consistent with an immunoglobulin E-mediated response requiring medical intervention. Because of a lack of intravenous access and because of limited availability of the oral suspension from the manufacturer, a desensitization protocol was implemented in which the intravenous formulation of linezolid was given orally. The patient was successfully desensitized by using an escalating, 14-dose procedure. We believe this is the first case in the English language literature to describe successful desensitization with the oral administration of intravenous linezolid in a patient with E. faecium bacteremia who was allergic to oxazolidinone.

The Risk of Hypersensitivity Reactions to Trimethoprim/Sulfamethoxazole as a Function of the CD4+ Count in HIV-Infected Patients

Background:

Trimethoprim/sulfamethoxazole (TMP/SMX) is an important antibiotic for the treatment and prevention of opportunistic infections in patients infected with HIV. However, the high rate of hypersensitivity reactions in this population of patients significantly limits the use of this drug.

Objective:

To determine whether early initiation of Pneumocystis carinii pneumonia prophylaxis with TMP/SMX in patients with HIV whose CD4+ lymphocyte count is >200 cells/mm3 results in a decrease in the number of hypersensitivity reactions.

Methods:

Retrospective cohort study. The main outcomes measured were the number of and the time to hypersensitivity reactions.

Results:

There were 134 patients who met the eligibility criteria (62 with a CD4+ cell count ≤200 cells/mm3 and 72 with a CD4+ cell count >200 cells/mm3). Overall, 47 (35.1%) patients had adverse reactions including 29 (21.6%) episodes of hypersensitivity. The mean time to a hypersensitivity reaction for the group with a CD4+ cell count ≤200 cells/mm3 was 155 days and for the group with a CD4+ cell count >200 cells/mm3 it was 261 days (mean difference = 106; p = 0.07; 95% CI 66 to 146 days). The number of episodes of hypersensitivity reactions was similar among the two groups: 15 (24.2%) and 14 (19.4%), respectively (p = 0.5; relative risk for CD4+ cell count ≤200 cells/mm3 = 1.14; 95% CI 0.7 to 1.7). Log-rank test did not reveal a significant difference in reaction-free survival among the groups (p = 0.3).

Conclusions:

Our data suggest that initiation of P. carinii pneumonia prophylaxis with TMP/SMX at a CD4+ cell count >200 cells/mm3 would lead to prolongation of the mean time to a hypersensitivity reaction, but would not significantly decrease the risk of a reaction over time.

Trimethoprim-sulfamethoxazole

After 25 years of use in the United States, trimethoprim-sulfamethoxazole (TMP-SMX) is widely prescribed for various indications. By virtue of sequential blockade of microbial folic acid synthesis, the antimicrobial combination has excellent in vitro inhibitory activity against many common respiratory and urinary tract pathogens, as well as many nosocomial infecting strains. In patients infected with the human immunodeficiency virus, TMP-SMX provides prophylactic and therapeutic potency against Pneumocystis carinii but at the risk of frequent side effects. TMP-SMX is also used for treatment of pulmonary and disseminated nocardiosis and some forms of Wegener's granulomatosis, as well as for prophylaxis of spontaneous bacterial peritonitis. Increasing bacterial resistance and concern about occasional severe adverse effects suggest that the usefulness of TMP-SMX may diminish in the future.

Efficacy of sulfamethoxypyridazine in a murine model of Pneumocystis carinii pneumonia

Sulfamethoxazole is the component of co-trimoxazole responsible for its efficacy against Pneumocystis carinii pneumonia, but this drug is associated with frequent adverse effects. Sulfamethoxypyridazine is significantly more effective than sulfamethoxazole against a murine model of P. carinii and might be a candidate for testing in infected patients.