Pharmacology, Dosing, and Side Effects of Rifabutin as a Possible Therapy for Antibiotic-Resistant Acinetobacter Infections

Current challenges in pulmonary nontuberculous mycobacterial infection: a case series with literature review

BACKGROUND

The prevalence of nontuberculous mycobacteria pulmonary disease (NTM-PD), particularly caused by Mycobacterium avium complex (MAC), is rising due to improved diagnostics, increased awareness, and more susceptible populations. NTM-PD significantly affects quality of life and imposes substantial economic costs. Understanding its clinical features, risk factors, and treatment challenges is vital for enhancing patient outcomes.

PATIENTS AND METHODS

A convenience sample from the University of Connecticut Health Center and Wayne State University involving patients with NTM-PD from 2021 to 2024 was studied retrospectively. Cases were selected to demonstrate typical diagnostic and treatment challenges, followed by a multidisciplinary roundtable discussion to examine patient-centered care strategies.

RESULTS

Analysis of six cases pinpointed chronic lung conditions and immunomodulatory therapy as key risk factors. Standard treatment, involving extensive multi-drug regimens, frequently results in poor adherence due to side effects and complex management requirements. The discussions underlined the importance of a customized, interdisciplinary approach to improve treatment effectiveness and patient quality of life.

CONCLUSIONS

NTM-PD is an escalating public health issue with notable clinical and economic consequences. Managing this disease effectively demands a comprehensive, patient-centered strategy that includes precise diagnosis, flexible treatment plans, and collaborative care.

Coadministration of Voriconazole and Rifabutin Can Increase the Risk of Adverse Drug Reactions in Patients with Multiple Infections

BACKGROUND

Coinfection of tuberculosis or nontuberculous mycobacteria and Aspergillus presents a challenge in medication selection because of the pharmacokinetic interactions between rifampin and voriconazole. Some researchers have suggested the use of rifabutin as an alternative to rifampin because of its lower hepatic cytochrome P450 enzyme induction potency despite its contraindication to drug labels. This study presents clinical cases of voriconazole and rifabutin coadministration and their potential risks.

METHODS

This retrospective study was conducted using clinical data from patients who met the following criteria: (1) admitted to Seoul National University Hospital between July 2014 and August 2023 and (2) concurrently administered rifabutin and voriconazole for more than 5 days.

RESULTS

Among the 6 patients analyzed, 4 experienced adverse drug reactions (ADRs). Three patients experienced visual and auditory hallucinations, lower extremity numbness, or delirious behavior. Two patients had prolonged the time from the start of the Q wave to the end of the T wave intervals, and 1 had elevated aspartate aminotransferase and alanine aminotransferase levels. In addition, 2 patients experienced severe nausea, poor oral intake, and weight loss. Despite receiving 1.81-fold the recommended voriconazole dosage, a therapeutic concentration (1.0-5.5 mg/L) was not achieved because of cytochrome P450 induction by rifabutin. However, during septic shock, the voriconazole concentration increased by 13.7- to 36-fold.

CONCLUSIONS

Concurrent use of rifabutin and voriconazole was associated with ADRs, including the time from the start of the Q wave to the end of the T wave prolongation, hallucinations, and severe nausea. Moreover, initially, there was a significant decrease in voriconazole concentrations; however, these concentrations substantially increased during septic shock. Therefore, it is essential to monitor drug concentrations and ADRs during concurrent use of voriconazole and rifabutin.

Treatment and Toxicity Considerations in Tuberculosis: A Narrative Review

Tuberculosis remains one of the most significant bacterial infections plaguing the medical community worldwide. The bacteria Mycobacterium tuberculosis retains the ability to manifest as an active infection, latent infection, miliary infection, or reactivation of latent infections in times of immunosuppression. Therefore, the medication regimen to treat the condition revolves around four medications, each with a mechanism that targets a different part of the bacteria. Isoniazid weakens the cell wall but produces neuropathy and hepatotoxicity as side effects. Rifampin interrupts protein synthesis but creates the opportunity for many drug-to-drug interactions and red-orange discolorations as side effects. Pyrazinamide is poorly understood, but it is believed to acidify the internal environment of the bacteria, with gout exacerbations and arthralgias as major side effects. Ethambutol also works as a bacteriostatic medication to interrupt the cell membrane; however, its mechanism is poorly understood. The most concerning side effect is optic neuropathy. The unfavorable side effect profile for tuberculosis treatment may contribute to the higher rates of medication noncompliance with therapy and needs to be addressed in the future.

Treatment Strategies of Colistin Resistance Acinetobacter baumannii Infections

Acinetobacter baumannii has emerged as a pressing challenge in clinical practice, mainly due to the development of resistance to multiple antibiotics, including colistin, one of the last-resort treatments. This review highlights all the possible mechanisms of colistin resistance and the genetic basis contributing to this resistance, such as modifications to lipopolysaccharide or lipid A structures, alterations in outer membrane permeability via porins and heteroresistance. In light of this escalating threat, the review also evaluates available treatment options. The development of new antibiotics (cefiderocol, sulbactam/durlobactam) although not available everywhere, and the use of various combinations and synergistic drug combinations (including two or more of the following: a polymyxin, ampicillin/sulbactam, carbapenems, fosfomycin, tigecycline/minocycline, a rifamycin, and aminoglycosides) are discussed in the context of overcoming colistin resistance of A. baumannii infections. Although most studied combinations are polymyxin-based combinations, non-polymyxin-based combinations have been emerging as promising options. However, clinical data remain limited and continued investigation is essential to determine optimal therapeutic strategies against colistin-resistant A. baumannii.

Using Dynamic Oral Dosing of Rifapentine and Rifabutin to Simulate Exposure Profiles of Long-Acting Formulations in a Mouse Model of Tuberculosis Preventive Therapy

Administration of tuberculosis preventive therapy (TPT) to individuals with latent tuberculosis infection is an important facet of global tuberculosis control. The use of long-acting injectable (LAI) drug formulations may simplify and shorten regimens for this indication. Rifapentine and rifabutin have antituberculosis activity and physiochemical properties suitable for LAI formulation, but there are limited data available for determining the target exposure profiles required for efficacy in TPT regimens. The objective of this study was to determine exposure-activity profiles of rifapentine and rifabutin to inform development of LAI formulations for TPT. We used a validated paucibacillary mouse model of TPT in combination with dynamic oral dosing of both drugs to simulate and understand exposure-activity relationships to inform posology for future LAI formulations. This work identified several LAI-like exposure profiles of rifapentine and rifabutin that, if achieved by LAI formulations, could be efficacious as TPT regimens and thus can serve as experimentally determined targets for novel LAI formulations of these drugs. We present novel methodology to understand the exposure-response relationship and inform the value proposition for investment in development of LAI formulations that have utility beyond latent tuberculosis infection.

Physiologically-based pharmacokinetic modelling to predict intragastric rifabutin concentrations in the treatment of Helicobacter pylori infection

BACKGROUND

Sustained intragastric antibiotic exposure is important for Helicobacter pylori eradication, yet little is known about gastric pharmacology of commonly used H. pylori regimens. For rifabutin, differing intragastric concentrations based on dosing regimen may account for differences in reported eradication rates.

AIM

To compare intragastric rifabutin concentrations between low-dose rifabutin (50 mg three time daily; as in RHB-105) and generically dosed rifabutin 150 mg once daily, 150 mg twice daily, and 300 mg once daily using a validated Physiologically-based pharmacokinetic (PBPK) model.

METHODS

We obtained plasma pharmacokinetic data from the RHB-105 clinical development programs and used it to develop and validate a whole-body PBPK model using PK-SIM software. We modified the existing rifabutin model to include the impact of omeprazole on gastric pH and emptying time. Modelled intragastric rifabutin exposure was expressed as the time that each regimen maintained its concentration ≥MIC90 .

RESULTS

Rifabutin 50 mg three times daily achieved significantly longer times with intragastric concentration above MIC90 (22.3 ± 1.1 h) than 150 mg once daily (8.3 ± 1.7 h), 150 mg twice daily (16.3 ± 2.3 h), or 300 mg once daily (8.5 ± 1.9 h) while providing the lowest mean maximal plasma concentration and mean area under the plasma concentration-time curve of all regimens studied.

CONCLUSIONS

PBPK modelling showed rifabutin 50 mg three times daily had higher intragastric exposure times than 150 mg once daily or twice daily, or 300 mg once daily. This low-dose rifabutin regimen provides the highest potential for H. pylori eradication while minimising systemic rifabutin exposure.

Using dynamic oral dosing of rifapentine and rifabutin to simulate exposure profiles of long-acting formulations in a mouse model of tuberculosis preventive therapy

Administration of tuberculosis preventive therapy (TPT) to individuals with latent tuberculosis infection is an important facet of global tuberculosis control. The use of long-acting injectable (LAI) drug formulations may simplify and shorten regimens for this indication. Rifapentine and rifabutin have anti-tuberculosis activity and physiochemical properties suitable for LAI formulation, but there are limited data available for determining the target exposure profiles required for efficacy in TPT regimens. The objective of this study was to determine exposure-activity profiles of rifapentine and rifabutin to inform development of LAI formulations for TPT. We utilized a validated paucibacillary mouse model of TPT in combination with dynamic oral dosing of both drugs to simulate and understand exposure-activity relationships to inform posology for future LAI formulations. This work identified several LAI-like exposure profiles of rifapentine and rifabutin that, if achieved by LAI formulations, could be efficacious as TPT regimens and thus can serve as experimentally-determined targets for novel LAI formulations of these drugs. We present novel methodology to understand the exposure-response relationship and inform the value proposition for investment in development of LAI formulations that has utility beyond latent tuberculosis infection.

Clinical Study of Different Treatment Methods for Tuberculous Pleuritis Complicated with Pleural Tuberculoma

Objective

To compare the clinical efficacy and adverse drug reactions of four different schemes in the treatment of pleural tuberculoma.

Methods

A total of 120 patients with pleural tuberculoma admitted to the Tuberculosis Department of our hospital from January 2018 to January 2021 were selected as the research subjects. According to different treatment methods, the patients were divided into four groups, with 30 cases in each group. They were as follows: group A received classical HRZE regimen, group B received HRZE+pleural injection, group C received HZE+rifabutin, and group D received HZE+rifabutin+pleural injection. All patients were treated intensively for 3 months and then consolidated treatment for 6 months according to the patient's condition. The absorption of lesions in the four groups at different time was compared, and the occurrences of adverse drug reactions and treatment outcomes during treatment were recorded.

Results

After 3 months of treatment, compared with groups A, B, and C, the number of significantly absorbed cases and effective cases in group D increased, while the number of invalid cases decreased. However, there was no statistical significance in the absorption of lesions between the four groups (χ² = 8.272, P = 0.507). In addition, pairwise comparison showed no significant difference in the absorption of lesions (P > 0.05). After 9 months of treatment, there was no significant difference in the absorption of lesions among the four groups (χ² = 8.795, P = 0.185), but the absorption of lesions in group D was significantly better than that in group A (P < 0.05). During treatment, the incidence of adverse reactions in the four groups was significantly different (χ² = 8.779, P = 0.032). Pairwise comparison showed that the incidence of adverse reactions in groups C and D was significantly lower than that in group A (P < 0.05). The total treatment course of group A was 9-16 months, and 10 cases (33.33%) still had residual lesions or pleural thickening at the end of treatment. The total course of treatment in group B was 9-12 months, and 7 cases (23.33%) still had residual lesions or pleural thickening at the end of the course of treatment. The total treatment course of group C was 9-16 months, and 8 cases (26.67%) still had residual lesions or pleural thickening at the end of treatment. The total course of treatment in group D was 9-12months, and there were still 2 cases of residual lesions (6.67%) at the end of the course.

Conclusions

HZE+rifabutin+pleural injection against tuberculosis therapy has a significant clinical efficacy in the treatment of pleural tuberculoma, which can more effectively improve the clinical symptoms of patients, improve the efficacy, and reduce complications, with a good prognosis, worthy of clinical promotion.

Efficacy and safety of low-dose rifabutin-based 7-day triple therapy as a third- or later-line Helicobacter pylori eradication regimen

BACKGROUND

Rifabutin-based regimens are used as rescue therapy for refractory Helicobacter pylori infection; however, the duration for which treatment is required and side effects are concerning. This study assessed the efficacy and safety of 7-day rifabutin, amoxicillin, and vonoprazan triple therapy as third- or later-line treatment for H. pylori infection.

MATERIALS AND METHODS

Patients who did not respond to second-line therapy were enrolled. After H. pylori infection was confirmed with the culture method, the patients received rifabutin-containing triple therapy (20 mg vonoprazan b.i.d., 500 mg amoxicillin q.i.d., and 150 mg rifabutin q.d.) for 7 days. Twelve weeks after the eradication therapy, successful eradication was confirmed using a ¹³ C urea breath test or the H. pylori stool antigen test. The results obtained from our previous study that reported a 10-day or 14-day esomeprazole based rifabutin-containing triple therapy as a third- or fourth-line rescue therapy treated patients were used as historical control. We determined the minimum inhibitory concentrations of amoxicillin and rifabutin. We also evaluated whether the patients were positive for the mutation of the rpoB gene.

RESULTS

Intention-to-treat and per-protocol analyses showed that our regimen resulted in a high eradication rate (91.2%, 95% CI: 84%-99% and 92.7%, 95% CI: 86%-100%, respectively). Adverse events occurred in 31.6% of the patients, and two patients discontinued the therapy.

CONCLUSIONS

This is the first study to evaluate the efficacy and safety of a 7-day low-dose rifabutin-based triple therapy with vonoprazan and amoxicillin. Our results suggest that our regimen was effective and safe as a third- or later-line H. pylori eradication regimen. To clarify what component in this regimen are critical, subsequent studies using a factorial design (comparing vonoprazan-amoxicillin dual therapy vs. vonoprazan-rifabutin triple therapy) will be needed.

In Vitro Activity of Rifabutin and Rifampin against Antibiotic-Resistant Acinetobacter baumannii, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae

We recently reported that the antimicrobial activity of rifabutin against Acinetobacter baumannii is best modeled by the use of RPMI for in vitro susceptibility testing. Here, we define the effects of medium on the susceptibility and frequency of resistance emergence in a panel of A. baumannii, Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa clinical isolates. Only A. baumannii was hypersusceptible to rifabutin in vitro and in vivo using a Galleria mellonella infection model. In vitro, the frequency of resistance emergence was greater when the bacteria were selected on RPMI versus tryptic soy agar (TSA) or Mueller-Hinton II (MHII) agar plates. However, the frequency of resistance emergence was lower in vivo than in the RPMI in vitro condition. IMPORTANCE Rifabutin has been recently described as a potential adjunctive therapy for antibiotic-resistant A. baumannii infections due to hypersensitivity in iron-depleted media, which may more closely mimic an in vivo environment. Here, we report that this hyperactivity is specific for A. baumannii, rather than being a general effect for other pathogens.

Infectious Diseases Society of America Guidance on the Treatment of AmpC β-lactamase-Producing Enterobacterales, Carbapenem-Resistant Acinetobacter baumannii, and Stenotrophomonas maltophilia Infections

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. A previous guidance document focused on infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa). Here, guidance is provided for treating AmpC β-lactamase-producing Enterobacterales (AmpC-E), carbapenem-resistant Acinetobacter baumannii (CRAB), and Stenotrophomonas maltophilia infections.

METHODS

A panel of six infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated questions about the treatment of AmpC-E, CRAB, and S. maltophilia infections. Answers are presented as suggestions and corresponding rationales. In contrast to guidance in the previous document, published data on optimal treatment of AmpC-E, CRAB, and S. maltophilia infections are limited. As such, guidance in this document is provided as "suggested approaches" based on clinical experience, expert opinion, and a review of the available literature. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment suggestions are provided, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Suggestions apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of September 17, 2021 and will be updated annually. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance-2.0/.

Rifabutin for infusion (BV100) for the treatment of severe carbapenem-resistant Acinetobacter baumannii infections

Rifamycin antibiotics were discovered during the 1950s, and their main representative, rifampicin, remains a cornerstone treatment for TB. The clinical use of rifamycin is restricted to mycobacteria and Gram-positive infections because of its poor ability to penetrate the Gram-negative outer membrane. Rifabutin, a rifamycin antibiotic approved for the prevention of Mycobacterium avium complex disease, makes an exception to this rule by hijacking the iron uptake system of Acinetobacter baumannii, resulting in potent activity against this important Gram-negative pathogen. Here, we describe recent findings on the specific activity of rifabutin and provide evidence of the need for the development of an intravenous formulation of rifabutin (BV100) for the treatment of difficult-to-treat carbapenem-resistant A.baumannii infections.