Dose-limiting toxicity of rifabutin in AIDS-related complex: syndrome of arthralgia/arthritis

Advancing the chemotherapy of tuberculous meningitis: a consensus view

Tuberculous meningitis causes death or disability in approximately 50% of affected individuals and kills approximately 78 200 adults every year. Antimicrobial treatment is based on regimens used for pulmonary tuberculosis, which overlooks important differences between lung and brain drug distributions. Tuberculous meningitis has a profound inflammatory component, yet only adjunctive corticosteroids have shown clear benefit. There is an active pipeline of new antitubercular drugs, and the advent of biological agents targeted at specific inflammatory pathways promises a new era of improved tuberculous meningitis treatment and outcomes. Yet, to date, tuberculous meningitis trials have been small, underpowered, heterogeneous, poorly generalisable, and have had little effect on policy and practice. Progress is slow, and a new approach is required. In this Personal View, a global consortium of tuberculous meningitis researchers articulate a coordinated, definitive way ahead via globally conducted clinical trials of novel drugs and regimens to advance treatment and improve outcomes for this life-threatening infection.

Rifabutin central nervous system concentrations in a rabbit model of tuberculous meningitis

Tuberculous meningitis (TBM) has a high mortality, possibly due to suboptimal therapy. Drug exposure data of antituberculosis agents in the central nervous system (CNS) are required to develop more effective regimens. Rifabutin is a rifamycin equivalently potent to rifampin in human pulmonary tuberculosis. Here, we show that human-equivalent doses of rifabutin achieved potentially therapeutic exposure in relevant CNS tissues in a rabbit model of TBM, supporting further evaluation in clinical trials.

Small molecule inhibitors of α-synuclein oligomers identified by targeting early dopamine-mediated motor impairment in C. elegans

BACKGROUND

Parkinson's disease is a disabling neurodegenerative movement disorder characterized by dopaminergic neuron loss induced by α-synuclein oligomers. There is an urgent need for disease-modifying therapies for Parkinson's disease, but drug discovery is challenged by lack of in vivo models that recapitulate early stages of neurodegeneration. Invertebrate organisms, such as the nematode worm Caenorhabditis elegans, provide in vivo models of human disease processes that can be instrumental for initial pharmacological studies.

METHODS

To identify early motor impairment of animals expressing α-synuclein in dopaminergic neurons, we first used a custom-built tracking microscope that captures locomotion of single C. elegans with high spatial and temporal resolution. Next, we devised a method for semi-automated and blinded quantification of motor impairment for a population of simultaneously recorded animals with multi-worm tracking and custom image processing. We then used genetic and pharmacological methods to define the features of early motor dysfunction of α-synuclein-expressing C. elegans. Finally, we applied the C. elegans model to a drug repurposing screen by combining it with an artificial intelligence platform and cell culture system to identify small molecules that inhibit α-synuclein oligomers. Screen hits were validated using in vitro and in vivo mammalian models.

RESULTS

We found a previously undescribed motor phenotype in transgenic α-synuclein C. elegans that correlates with mutant or wild-type α-synuclein protein levels and results from dopaminergic neuron dysfunction, but precedes neuronal loss. Together with artificial intelligence-driven in silico and in vitro screening, this C. elegans model identified five compounds that reduced motor dysfunction induced by α-synuclein. Three of these compounds also decreased α-synuclein oligomers in mammalian neurons, including rifabutin which has not been previously investigated for Parkinson's disease. We found that treatment with rifabutin reduced nigrostriatal dopaminergic neurodegeneration due to α-synuclein in a rat model.

CONCLUSIONS

We identified a C. elegans locomotor abnormality due to dopaminergic neuron dysfunction that models early α-synuclein-mediated neurodegeneration. Our innovative approach applying this in vivo model to a multi-step drug repurposing screen, with artificial intelligence-driven in silico and in vitro methods, resulted in the discovery of at least one drug that may be repurposed as a disease-modifying therapy for Parkinson's disease.

A Comparative Insight on the Newly Emerging Rifamycins: Rifametane, Rifalazil, TNP-2092 and TNP-2198

Rifamycins are considered a milestone for tuberculosis (TB) treatment because of their proficient sterilizing ability. Currently, available TB treatments are complicated and need a long duration, which ultimately leads to failure of patient compliance. Some new rifamycin derivatives, i.e., rifametane, TNP-2092 (rifamycin-quinolizinonehybrid), and TNP-2198 (rifamycin-nitromidazole hybrid) are under clinical trials, which are attempting to overcome the problems associated with TB treatment. The undertaken review is intended to compare the pharmacokinetics, pharmacodynamics and safety profiles of these rifamycins, including rifalazil, another derivative terminated in phase II trials, and already approved rifamycins. The emerging resistance of microbes is an imperative consideration associated with antibiotics. Resistance development potential of microbial strains against rifamycins and an overview of chemistry, as well as structure-activity relationship (SAR) of rifamycins, are briefly described. Moreover, issues associated with rifamycins are discussed as well. We expect that newly emerging rifamycins shall appear as potential tools for TB treatment in the near future.

Drug-induced uveitis: A review

Uveitis maybe induced by the use of various medications known as drug-induced uveitis (DIU), though rare it is an important cause of uveitis which one needs to be aware of. The drugs may be administered through any route including systemic, topical, and intravitreal. Ocular inflammation can be in the form of anterior, intermediate, posterior or pan uveitis, and rarely may present as episcleritis and scleritis. Identification of drug as the offending agent of uveitis is important as many a times stopping the drug may help recover the uveitis or the concomitant use of corticosteroids. An extensive literature review was done using the Pubmed. An overview of DIU is provided as it is important for us to be aware of this clinical entity.

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

Acinetobacter baumannii has among the highest rates of antibiotic resistance encountered in hospitals. New therapies are critically needed. We found that rifabutin has previously unrecognized hyperactivity against most strains of A. baumannii. Here we review the pharmacology and adverse effects of rifabutin to inform potential oral dosing strategies in patients with A. baumannii infections. Rifabutin demonstrates dose-dependent increases in blood levels up to 900 mg per day, but plateaus thereafter. Furthermore, rifabutin induces its own metabolism after prolonged dosing, lowering its blood levels. Pending future development of an intravenous formulation, a rifabutin oral dose of 900-1200 mg per day for 1 week is a rational choice for adjunctive therapy of A. baumannii infections. This dosage maximizes AUC₂₄ to drive efficacy while simultaneously minimizing toxicity. Randomized controlled trials will be needed to definitively establish the safety and efficacy of rifabutin to treat A. baumannii infections.

Drug-induced Uveitis in HIV Patients with Ocular Opportunistic Infections

Purpose: To describe drug-induced uveitis in immunocompromised patients diagnosed with Human Immunodeficiency Virus (HIV) infection Methods: Narrative Review Results: Systemic and intraocular medications administered for the treatment of acquired immune deficiency syndrome (AIDS)-associated diseases in patients infected with HIV are a well-known cause of uveitis. Conclusions: Cidofovir and rifabutin, among other novel anti-retroviral therapies, are strongly associated with drug-induced uveitis. It is imperative to understand the pathogenesis, clinical findings, and management of HIV patients with uveitis induced by these agents.

Musculoskeletal manifestations of tuberculosis: An observational study

Background:

Data of musculoskeletal manifestations of tuberculosis (TB) are limited to case reports, series, or retrospective studies. Therefore, we conducted this study to create awareness among doctors about musculoskeletal manifestations of TB.

Materials and Methods:

This was a prospective observational study conducted at a referral TB Hospital in North India in September and October 2016. The aim of our study was to study musculoskeletal manifestations of TB. We included patients who had active TB as per the World Health Organization 2010 criteria. Patients with other chronic illnesses were excluded. A detailed history, examination, and appropriate investigations (blood, urine, serological, and radiological) of the 100 consecutive patients fulfilling the inclusion criteria were recorded.

Results:

The mean age of patients was 32.16 ± 12.93 years. Male-to-female ratio was 43:57. The mean duration of disease was 6.85 ± 8.83 months. Of the 100 patients, 60 (60%) had pulmonary TB. The mean duration of antitubercular therapy was 1.79 ± 1.34 months. Fibromyalgia was classified in 21 (21%) patients, polyarthralgia was seen in 9 (9%), Pott's spine in 7 (7%), osteomyelitis in 4 (4%), and scleritis in 2 (2%) patients. Uveitis, tenosynovitis, erythema induratum, subcutaneous abscess, and dactylitis were seen in 1 (1%) patient each. In 21 patients who had fibromyalgia, 11 developed fibromyalgia with the second episode of TB amounting to 60.75% patients.

Conclusion:

This is the first prospective study to look at the musculoskeletal manifestations of TB. Patients with active TB were found to have various rheumatological manifestations.

Rifabutin: where do we stand in 2016?

Rifabutin is a spiro-piperidyl-rifamycin structurally closely related to rifampicin that shares many of its properties. We attempted to address the reasons why this drug, which was recently recognized as a WHO Essential Medicine, still had a far narrower range of indications than rifampicin, 24 years after its launch. In this comprehensive review of the classic and more recent rifabutin experimental and clinical studies, the current state of knowledge about rifabutin is depicted, relying on specific pharmacokinetics, pharmacodynamics, antimicrobial properties, resistance data and side effects compared with rifampicin. There are consistent in vitro data and clinical studies showing that rifabutin has at least equivalent activity/efficacy and acceptable tolerance compared with rifampicin in TB and non-tuberculous mycobacterial diseases. Clinical studies have emphasized the clinical benefits of low rifabutin liver induction in patients with AIDS under PIs, in solid organ transplant patients under immunosuppressive drugs or in patients presenting intolerable side effects related to rifampicin. The contribution of rifabutin for rifampicin-resistant, but rifabutin-susceptible, Mycobacterium tuberculosis isolates according to the present breakpoints has been challenged and is now controversial. Compared with rifampicin, rifabutin's lower AUC is balanced by higher intracellular penetration and lower MIC for most pathogens. Clinical studies are lacking in non-mycobacterial infections.

Drug-induced uveitis

INTRODUCTION

Drug-induced uveitis is a well described but often overlooked and/or misdiagnosed adverse reaction to medication. There are an increasing number of medications that have been related to the onset of intraocular inflammation. Identification of these inciting agents may decisively help the diagnostic algorithm involving new cases of uveitis.

AREAS COVERED

This review intends to be an updated comprehensive, practical guide for practitioners regarding the main drugs that have been associated with uveitis. A classification proposed by Naranjo et al. in 1981 for establishing potential causality is applied examining possible mechanisms of action. A guide for clinicians about the rationale of these observations when dealing with patients with uveitis is provided.

EXPERT OPINION

Several agents with different routes of administration (systemic, topical and/or intraocular) may cause intraocular inflammation. The mechanism behind ocular inflammation is frequently unknown. Clinicians should be aware of the potential drug effect to optimize diagnosis and management of such patients.

Drug-induced uveitis

A number of medications have been associated with uveitis. This review highlights both well-established and recently reported systemic, topical, intraocular, and vaccine-associated causes of drug-induced uveitis, and assigns a quantitative score to each medication based upon criteria originally described by Naranjo and associates.

Drug-induced lupus associated with rifabutin: a literature review

Drug-induced lupus (DIL) is a rare adverse reaction to medications with features resembling idiopathic systemic lupus erythromatosis. Rifabutin/rifamycins have only rarely been reported as a cause of DIL, and no cases have been reported in blacks. A 55-year-old African American woman with HIV presented with severe generalized arthralgias and recurrent oral ulcers while receiving treatment for tuberculous meningitis. Arthralgias, which began in her knees after 5 weeks of antituberculous therapy, progressed to involve the joints in the ankles, wrists, and hands. She had no associated fever or rash. When she had these symptoms her antinuclear antibody (ANA) was 1:1280 homogenous pattern, antidouble stranded DNA was negative, antihistone antibody was strongly positive, anti-smith and antiribonucleoprotein (anti-RNP) were negative. Her symptoms resolved within 2 months of stopping rifabutin while continuing other antituberculous medications and her ANA titer started to decrease. We review the existing literature on this subject.

Rifabutin-Induced Thrombocytopenia from Concurrent Use of High-Dose Fluconazole

Objective:

To report a case of—and review the literature supporting—rifabutin-induced thrombocytopenia from concurrent use of high-dose fluconazole.

Case Summary:

A 34-year-old man with AIDS, on a stable regimen that included rifabutin and fluconazole for the previous 3 months, was admitted to the hospital with symptoms of oropharyngeal candidiasis. He was treated with increased doses of fluconazole 200 mg to 800 mg daily over a 9-day hospital admission. During this time, his platelet count decreased from 441,000 cells/mm3 to 24,000 cells/mm3, with no signs of bleeding. He was discharged on day 9 and instructed to omit 1 dose of rifabutin and continue fluconazole 200 mg daily. On day 12, his platelet count was 118,000 cells/mm3. About 1 month after discharge, his platelet count was 151,000 cells/mm3.

Discussion:

Rifabutin is known to cause thrombocytopenia. Results from initial studies evaluating various doses of rifabutin were not conclusive as to whether rifabutin-induced thrombocytopenia is a dose-dependent effect. With increased use of rifabutin, often in combination with potentially interacting medications, reports of thrombocytopenia have gained frequency. One study showed that patients on higher doses of rifabutin experienced thrombocytopenia significantly more often than did those on lower doses. When rifabutin is administered with fluconazole, there is a clear pharmacokinetic interaction, showing a 76–82% increase in the rifabutin area under the concentration curve, with only uveitis and leukopenia reported. An objective causality assessment of this case classified the interaction between fluconazole and rifabutin, resulting in thrombocytopenia, as probable. Other causes of thrombocytopenia in our patient, including AIDS, Mycobacterium avium complex, fluconazole, famotidine, and ritonavir, are less likely.

Conclusions:

We describe the first case of rifabutin-induced thrombocytopenia from concurrent use of high-dose fluconazole. There is evidence to support this interaction and practitioners should be aware of this potential adverse effect.

Rifabutin-Associated Panuveitis with Retinal Vasculitis in Pulmonary Tuberculosis

INTRODUCTION

Rifabutin-associated uveitis has been reported frequently in AIDS patients and more rarely in immunocompetent patients. It is characterized clinically by anterior acute uveitis. Only a few poorly documented cases of rifabutin-induced panuveitis with retinal vasculitis have been reported. Here, we report four cases of rifabutin-associated panuveitis with retinal vasculitis.

CASE REPORTS

We describe four patients with active tuberculosis, treated with a multidrug regimen including rifabutin for at least 1.5 months before presentation. The first patient was immunocompetent, the three others had AIDS and were undergoing triple anti-HIV therapy. Three patients were women with a low body weight. All four patients presented with panuveitis and retinal vasculitis. Interruption of the drug rapidly reduced the ocular inflammation in all cases.

CONCLUSION

Four cases of rifabutin-associated panuveitis with retinal vasculitis are reported in patients with active pulmonary tuberculosis. Immunogenicity of Mycobacterium tuberculosis as well as the very low weight of the patients might be implicated in the development of this unusual form of rifabutin-associated uveitis.

Anterior Segment and External Ocular Disorders Associated with Human Immunodeficiency Virus Disease

The eye is a common site for complications of human immunodeficiency virus (HIV) infection. Although cytomegalovirus retinitis remains the most prevalent of the blinding ocular disorders that can occur in individuals with the acquired immunodeficiency syndrome (AIDS), several important HIV-associated disorders may involve the anterior segment, ocular surface, and adnexae. Some of these entities, such as Kaposi sarcoma, were well described, but uncommon, before the HIV epidemic. Others, like microsporidial keratoconjunctivitis, have presentations that differ between affected individuals with HIV disease and those from the general population who are immunocompetent. The treatment of many of these diseases is challenging because of host immunodeficiency. Survival after the diagnosis of AIDS has increased among individuals with HIV disease because of more effective antiretroviral therapies and improved prophylaxis against, and treatment of, opportunistic infections. This longer survival may lead to an increased prevalence of anterior segment and external ocular disorders. In addition, the evaluation and management of disorders such as blepharitis and dry eye, which were previously overshadowed by more severe, blinding disorders, may demand increased attention, as the general health of this population improves. Not all individuals infected with HIV receive potent antiretroviral therapy, however, because of socioeconomic or other factors, and others will be intolerant of these drugs or experience drug failure. Ophthalmologists must, therefore, still be aware of the ocular findings that develop in the setting of severe immunosuppression. This article reviews the spectrum of HIV-associated anterior segment and external ocular disorders, with recommendations for their evaluation and management.

The ever-expanding association between rheumatologic diseases and tuberculosis

We summarized most of the rheumatologic manifestations of tuberculosis (TB) and the occurrence of Mycobacterium tuberculosis disease associated with rheumatologic diseases. We established 4 different categories: (1) direct musculoskeletal involvement of M. tuberculosis, including spondylitis, osteomyelitis, septic arthritis, and tenosynovitis; (2) M. tuberculosis as an infectious pathogen in rheumatologic diseases, particularly with the use of newer agents such as tumor necrosis factor-alpha inhibitors; (3) antimycobacterial drug-induced rheumatologic syndromes, including tendinopathy, drug-induced lupus, and others; and (4) reactive immunologic phenomena caused by TB, such as reactive arthritis, erythema nodosum, and others. In addition, Bacille-Calmette-Guérin vaccination used for the prevention of TB or as a chemotherapeutic agent for bladder carcinoma also may be associated with musculoskeletal adverse events. We conclude that M. tuberculosis can directly or indirectly affect the musculoskeletal system.

Rifampicin-induced lupus erythematosus

Rifampicin has been prescribed throughout the world for over 20 years, yet only four cases of rifampicin-induced lupus erythematosus (LE) have been reported. Rifampicin-induced LE is associated with combination therapy with clarithromycin or ciprofloxacin. These drugs are all metabolized through the cytochrome P450 liver enzyme system and combined usage may lead to higher rifampicin blood levels. Drug-induced LE differs from systemic LE; cutaneous manifestations, although uncommon, are an important clue to the diagnosis. We report a case of rifampicin-induced LE presenting with florid cutaneous features.

Idiosyncratic rifabutin-induced leukopenia and SIADH: case report and review

Rifabutin is increasingly critical for treatment of atypical mycobacterial infections. One of its serious adverse effects is leukopenia. When encountering rifabutin-induced leukopenia, clinicians are faced with the dilemma of whether to lower the dosage of rifabutin or discontinue it because existing literature does not indicate whether rifabutin-induced leukopenia is dose related or idiosyncratic. We report the first established case of idiosyncratic rifabutin-induced leukopenia in an immunocompetent man treated for pulmonary Mycobacterium avium complex infection. The patient also developed rifabutin-induced syndrome of inappropriate antidiuretic hormone (SIADH), which also has not been previously reported.

Pharmacokinetic Interaction between amprenavir and rifabutin or rifampin in healthy males

The objective of this study was to determine if there is a pharmacokinetic interaction when amprenavir is given with rifabutin or rifampin and to determine the effects of these drugs on the erythromycin breath test (ERMBT). Twenty-four healthy male subjects were randomized to one of two cohorts. All subjects received amprenavir (1,200 mg twice a day) for 4 days, followed by a 7-day washout period, followed by either rifabutin (300 mg once a day [QD]) (cohort 1) or rifampin (600 mg QD) (cohort 2) for 14 days. Cohort 1 then received amprenavir plus rifabutin for 10 days, and cohort 2 received amprenavir plus rifampin for 4 days. Serial plasma and urine samples for measurement of amprenavir, rifabutin, and rifampin and their 25-O-desacetyl metabolites, were measured by high-performance liquid chromatography. Rifabutin did not significantly affect amprenavir's pharmacokinetics. Amprenavir significantly increased the area under the curve at steady state (AUC(ss)) of rifabutin by 2.93-fold and the AUC(ss) of 25-O-desacetylrifabutin by 13.3-fold. Rifampin significantly decreased the AUC(ss) of amprenavir by 82%, but amprenavir had no effect on rifampin pharmacokinetics. Amprenavir decreased the results of the ERMBT by 83%. The results of the ERMBT after 2 weeks of rifabutin and rifampin therapy were increased 187 and 156%, respectively. Amprenavir plus rifampin was well tolerated. Amprenavir plus rifabutin was poorly tolerated, and 5 of 11 subjects discontinued therapy. Rifampin markedly increases the metabolic clearance of amprenavir, and coadministration is contraindicated. Amprenavir significantly decreases clearance of rifabutin and 25-O-desacetylrifabutin, and the combination is poorly tolerated. Amprenavir inhibits the ERMBT, and rifampin and rifabutin are equipotent inducers of the ERMBT.

Risk-benefit assessment of therapies for Mycobacterium avium complex infections

Mycobacterium avium complex (MAC) is an important pathogen that can cause chronic lung disease in immunocompetent patients and disseminated disease in patients with the acquired immunodeficiency syndrome (AIDS). Treatment of MAC with antituberculosis drugs was unsatisfactory, but the introduction of the newer macrolides, clarithromycin and azithromycin, and of rifabutin has greatly improved the outcome of treatment regimens for MAC. However, these agents are also associated with many new treatment-related adverse effects and potential drug-drug interactions. Rifamycins [rifampicin (rifampin) more than rifabutin] induce cytochrome P450 enzymes and accelerate the metabolism of clarithromycin and HIV protease inhibitors. Conversely, clarithromycin inhibits these enzymes, resulting in increased rifabutin toxicity. The net results are treatment regimens that may be extremely difficult to tolerate, especially for elderly or debilitated patients. Clarithromycin and azithromycin must be administered in combination with other agents such as ethambutol to prevent the emergence of macrolide resistance. Unfortunately, not all patients respond to the combination of a macrolide, rifabutin and ethambutol, and many have significant adverse effects (mostly gastrointestinal) with this regimen. For some patients the treatment is worse than the disease. The same 3-drug regimen is also effective therapy for disseminated MAC in AIDS patients, in whom the additional problem of a rifamycin/protease inhibitor interaction may be present. Fortunately, as opposed to pulmonary MAC disease in immunocompetent patients, disseminated MAC disease is a diminishing problem because of effective prophylactic regimens for MAC and improved antiretroviral therapy for HIV. Significant progress has been made in the treatment of MAC disease with the introduction of the newer macrolides. It is to be hoped that even better drugs that are more active against MAC and are associated with less toxicity and drug-drug interactions will be introduced in the future.

Corneal endothelial deposits in children positive for human immunodeficiency virus receiving rifabutin prophylaxis for Mycobacterium avium complex bacteremia

PURPOSE

To assess the potential ocular effects of prophylactic administration of rifabutin in children with symptomatic human immunodeficiency virus (HIV) infection and CD4 counts less than 50 cells per mm3.

METHODS

Twenty-five children with HIV infection were enrolled in a phase I-II study of prophylactic administration of systemic rifabutin for prevention of disseminated Mycobacterium avium complex infection and monitored prospectively for the development of ocular complications secondary to HIV infection or drug toxicity.

RESULTS

The dose of rifabutin ranged from 5.0 mg to 15.0 mg per kg, and the median ophthalmic follow-up was 24 months. During the study period, six of the children receiving rifabutin prophylaxis for M. avium complex developed unusual bilateral, initially peripheral, stellate, corneal endothelial deposits without associated uveitis. Review of serial corneal drawings and photographs showed an increase in the number of corneal deposits with continued administration of rifabutin. The duration of rifabutin treatment (P = .017) and follow-up (P = .0011) was significantly longer in patients who developed these corneal endothelial changes.

CONCLUSION

Corneal endothelial deposits should be considered a potential side effect of rifabutin therapy. To date, these findings have not been sight threatening.

Drug-induced uveitis

Uveitis has been reported in association with a variety of topical, intraocular, periocular, and systemic medications. To establish causality of adverse events by drugs, in 1981, Naranjo and associates proposed seven criteria, which are related to the frequency and documentation of the event; circumstances of occurrence, recovery, and recurrence; and coexistence of other factors or medications. Rarely does a drug meet all seven criteria. The authors review reports of drug-associated uveitis, applying the seven criteria and examining possible mechanisms. Only systemically administered biphosphonates and, perhaps, topical metipranolol meet all seven criteria. Systemic sulfonamides, rifabutin, and topical glucocorticoids fulfill at least five criteria.

HIV infection-associated inflammatory musculoskeletal disorders

Inflammatory musculoskeletal complaints are relatively common during the course of HIV infection, although they tend to be more frequent during late stages. The clinical spectrum is varied, ranging from arthralgias to distinct rheumatic disorders, such as Reiter's syndrome and psoriatic arthritis. The therapeutic management often poses a challenge, although most patients respond to conventional first- and second-line anti-inflammatory medications.

The effect of multiple doses of ritonavir on the pharmacokinetics of rifabutin

OBJECTIVE

To investigate the effects of ritonavir on the pharmacokinetics of rifabutin.

METHODS

In a multiple-dose, randomized, parallel-group, double-blind study, subjects received 150 mg rifabutin daily for 24 days coadministered on days 15 to 24 with twice-daily doses of either placebo or ritonavir (300 mg on day 15, 400 mg on day 16, and 500 mg on days 17 to 24). Plasma concentrations of rifabutin and 25-O-desacetylrifabutin were measured by HPLC, and the pharmacokinetics were determined after the rifabutin doses on days 14 and 24.

RESULTS

For subjects receiving rifabutin and placebo who completed the study (n = 11), there were small but statistically significant differences (< or = 32%) in several rifabutin and 25-O-desacetylrifabutin pharmacokinetic parameters between the regimens of rifabutin alone and rifabutin with placebo. In contrast, the effect of ritonavir on rifabutin pharmacokinetics of subjects completing the study (n = 5) was substantial. Rifabutin mean minimum observed concentration (Cmin), maximum observed concentration (Cmax), and area under the concentration-time curve [AUC(0-24)] increased by approximately sixfold, 2.5-fold, and fourfold, respectively, and 25-O-desacetylrifabutin mean Cmin, Cmax, and AUC(0-24) increased by approximately 200-, 16-, and 35-fold, respectively, when coadministered with ritonavir compared with rifabutin administered alone. The sum of the mean AUC(0-24) of rifabutin and 25-O-desacetylrifabutin increased nearly sevenfold when coadministered with ritonavir.

CONCLUSIONS

Ritonavir inhibited the metabolism of rifabutin and 25-O-desacetylrifabutin, suggesting that both are metabolized at least in part by CYP3A. Ritonavir may have enhanced rifabutin bioavailability by reducing either intestinal of hepatic metabolism of both. Clarithromycin is an alternative to rifabutin for antimycobacterial therapy that may be administered concurrently with ritonavir. Administration of ritonavir with a reduced rifabutin dosage regimen (150 mg every Monday, Wednesday, and Friday) is being investigated.

Chronic multifocal retinal infiltrates in patients infected with human immunodeficiency virus

PURPOSE

To describe the clinical features of a disorder characterized by chronic multifocal retinal infiltrates and uveitis in individuals with human immunodeficiency virus (HIV) disease.

METHODS

We reviewed the medical records of HIV-infected patients with multifocal retinal infiltrates of unknown cause seen by investigators at four institutions. The following data were collected: demographic characteristics, presenting signs and symptoms, laboratory test results, and course of disease.

RESULTS

We identified 26 HIV-infected patients (50 involved eyes) with this syndrome. Median CD4+ T-lymphocyte count at presentation was 272 per microl (range, 7 to 2,118 per microl). The most common presenting symptom was floaters. Median visual acuity of involved eyes at presentation was 20/20 (range, 20/15 to 20/100) and remained stable (median, 20/20; range, 20/15 to 20/70) after a median follow-up period of 9 months (range, 0 to 110 months). Typical retinal lesions were gray-white or yellow, irregular in shape, and less than 200 microm in greatest dimension. All were located in the midperiphery or anterior retina and enlarged slowly or remained static in size. Mild to moderate anterior chamber or vitreous humor inflammatory cells were present in 47 of 50 eyes (26 of 26 patients). Retinal lesions possibly responded to zidovudine but not to acyclovir or ganciclovir. Anterior chamber and vitreous humor inflammatory reactions responded to topical or periocular injections of corticosteroid.

CONCLUSIONS

Uveitis with chronic multifocal retinal infiltrates is a distinct clinical entity of unknown cause that occurs in HIV-infected patients. Retinal lesions may respond to antiretroviral therapy. Visual prognosis is good.

Tolerance and pharmacokinetic interactions of rifabutin and clarithromycin in human immunodeficiency virus-infected volunteers

This study evaluated the tolerance and potential pharmacokinetic interactions between clarithromycin (500 mg every 12 h) and rifabutin (300 mg daily) in clinically stable human immunodeficiency virus-infected volunteers with CD4 counts of <200 cells/mm3. Thirty-four subjects were randomized equally to either regimen A or regimen B. On days 1 to 14, subjects assigned to regimen A received clarithromycin and subjects assigned to regimen B received rifabutin, and then both groups received both drugs on days 15 to 42. Of the 14 regimen A and the 15 regimen B subjects who started combination therapy, 1 subject in each group prematurely discontinued therapy due to toxicity, but 19 of 29 subjects reported nausea, vomiting, and/or diarrhea. Pharmacokinetic analysis included data for 11 regimen A and 14 regimen B subjects. Steady-state pharmacokinetic parameters for single-agent therapy (day 14) and combination therapy (day 42) were compared. Regimen A resulted in a mean decrease of 44% (P = 0.003) in the clarithromycin area under the plasma concentration-time curve (AUC), while there was a mean increase of 57% (P = 0.004) in the AUC of the clarithromycin metabolite 14-OH-clarithromycin. Regimen B resulted in a mean increase of 99% (P = 0.001) in the rifabutin AUC and a mean increase of 375% (P < 0.001) in the AUC of the rifabutin metabolite 25-O-desacetyl-rifabutin. The usefulness of this combination for prophylaxis of Mycobacterium avium infections is limited by frequent gastrointestinal adverse events. Coadministration of clarithromycin and rifabutin results in significant bidirectional pharmacokinetic interactions. The resulting increase in rifabutin levels may explain the increased frequency of uveitis observed with concomitant use of these drugs.

Uveitis associated with rifabutin and macrolide therapy for Mycobacterium avium intracellulare infection in AIDS patients

OBJECTIVE

Uveitis has been increasingly recognised as a side effect of rifabutin regimens in the prophylaxis and treatment of Mycobacterium avium intracellulare (MAI) infection. This study describes the clinical features and analyses the factors associated with rifabutin induced uveitis.

DESIGN

Retrospective observational study.

SETTING

Tertiary care institution, The Royal Hospitals NHS Trust, London.

PATIENTS

68 HIV seropositive individuals receiving rifabutin for prophylaxis or treatment of MAI infection.

RESULTS

11 episodes of uveitis occurred in 10 different individuals at a median of 62 days. The disease was bilateral in four and unilateral in the remainder. All subjects experienced ocular pain and photophobia and 9 individuals had a significant reduction in visual acuity. Uveitis was treated with mydriatics and topical steroids and resolved in all cases when rifabutin was stopped. The risk of uveitis was significantly increased with concurrent clarithromycin therapy, Odds Ratio 13.08, 95% Confidence Interval 1.98 to 83.12.

CONCLUSION

Rifabutin can cause a reversible uveitis. This risk is increased with concurrent clarithromycin therapy. Adverse drug interactions can be an important cause of morbidity in patients with advanced HIV disease.

Adverse effects and drug interactions of medications commonly used in the treatment of adult HIV positive patients

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Pattern of utilization of rifabutin for prophylaxis of Mycobacterium avium complex among patients with advanced human immunodeficiency virus disease in a community setting

OBJECTIVE

To characterize the pattern of utilization, effectiveness, and safety profile of rifabutin for Mycobacterium avium complex (MAC) prophylaxis among individuals with advanced human immunodeficiency virus disease in a community setting.

METHODS

Individuals who, while registered in the provincial drug distribution program, had at least one CD4 count below 100 cells/mm3 for the period 1 May 1993 to 31 March 1994 were included. MAC diagnoses were identified through a record linkage with the mycobacterial reference laboratory of the Provincial Centre for Disease Control. In order to determine the occurrence of adverse events, a survey was sent in March 1994 to the 98 primary care physicians prescribing rifabutin prophylaxis in the province. We achieved 100% response rate to the survey.

RESULTS

During the study period 515 patients in our drug treatment program were eligible to receive MAC prophylaxis. Of these, 340 (66%) were being prescribed rifabutin as recommended by current guidelines. Rifabutin prophylaxis use was significantly associated with use of antiretroviral therapy. The product limit estimate of the cumulative incidence of MAC at 10 months was 13.0% among those receiving rifabutin prophylaxis. Diagnosis of MAC was significantly associated with a lower baseline CD4 count (cumulative incidence 7.1% and 18.1% for CD4 > or = 50 and < 50 cells/mm3, respectively, P = 0.01). A total of four cases of uveitis, eight cases of pseudo-jaundice, and five cases of arthralgia in 16 patients were identified by our survey.

CONCLUSION

Our data demonstrates that rifabutin prophylaxis of MAC is being used by approximately 66% of eligible individuals. Rifabutin use was associated with antiretroviral use, which may reflect individuals' attitudes towards medications. Our intention-to-treat analysis, with a 10 month cumulative MAC incidence of 13.0% among those receiving rifabutin prophylaxis, is in keeping with break-through rates previously reported in the context of clinical trials. Our results also support previous observations that the risk of MAC infection greatly increases at CD4 counts < 50 cells/mm3. Rifabutin prophylaxis was generally well-tolerated in our program.

Rifabutin induced vitritis in AIDS patients

The authors report three patients with the acquired immunodeficiency syndrome (AIDS) who developed uveitis while prophylactically taking rifabutin (300 mg/kg or more), clarithromycin and fluconazole. The uveitis presented unilaterally, but became bilateral within seven days in each patient. Inflammation was more severe in the vitreous than in the anterior chamber. Examination of the vitreous and blood from one patient with microbiological smears, bacterial and fungal culture and the polymerase chain reaction (PCR) to herpesviruses did not reveal an infectious etiology. Discontinuation or decreasing the dose of rifabutin to 300 mg/day and treatment with topical steroids and cycloplegics resulted in resolution of the uveitis within two weeks. Our findings support the observation that prophylactic doses of rifabutin, combined with clarithromycin, fluconazole or other agents which can increase rifabutin levels, can induce uveitis in patients with AIDS. It is important to recognize that a severe vitritis which can obscure visualization of the retina can be solely attributed to rifabutin in patients with AIDS. Therapy requires lowering the dose of rifabutin and the use of topical corticosteroids and cycloplegics.

Anterior uveitis associated with rifabutin medication in AIDS patients

Eight episodes of rifabutin-associated anterior uveitis in AIDS patients are reported. Uveitis developed after two weeks to nine months of medication, commonly when rifabutin was administered along with clarithromycin and/or fluconazole. Recovery was closely correlated to suspending rifabutin early, while less dependent on total rifabutin dose or epidemiological patient characteristics. In two cases, discontinuation of rifabutin alone relieved ocular inflammation. Repeated exposure to rifabutin was successful with a reduced dosage in three patients.

Recurrent bilateral anterior uveitis with hypopyon and rifabutin therapy

Rifabutin is used in patients with human immunodeficiency virus infection to prevent and treat Mycobacterium avium complex infection. We report a case of recurrent bilateral anterior uveitis with hypopyon in a patient who was taking 600 mg of rifabutin daily. The rate of recurrence with the continuation of rifabutin seems to be high, especially in the opposite eye (alternate uveitis with hypopyon); rifabutin should be discontinued if uveitis recurs.

Uveitis associated with rifabutin therapy

PURPOSE

To highlight the association of uveitis with the use of rifabutin.

METHODS

Retrospective study of two patients with acute anterior uveitis.

RESULTS

Both patients were receiving rifabutin for treatment of atypical Mycobacterium infection associated with AIDS when they developed unilateral acute anterior uveitis and arthritis. The inflammation resolved and vision improved with introduction of topical corticosteroids, mydriatics and cessation of rifabutin treatment.

CONCLUSION

Use of rifabutin with clarithromycin may precipitate acute uveitis in patients with AIDS being treated for systemic Mycobacterium avium complex infection. Uveitis produced by rifabutin may be analogous to Herxeimer reaction as seen in syphilis. Clarithromycin and fluconazole elevate levels of rifabutin due to inhibition of metabolism through cytochrome p-450 pathway. The differential diagnosis includes Reiter's syndrome, syphilis causing uveitis, metastatic endophthalmitis, and direct HIV-related uveitis.

Rifabutin-associated uveitis

OBJECTIVE

To review rifabutin-associated uveitis and discuss the mechanism and potential role of drug interactions with clarithromycin and fluconazole in contributing to this adverse event.

DATA SOURCES

A MEDLINE search (1991 through September 1994) of English-language literature using the main MeSH headings "rifabutin" and "uveitis" and the subheadings "adverse effects" and "chemically induced." Relevant articles also were selected from references of identified articles. Abstracts from recent medical conferences of infectious diseases, pharmacology, and HIV were screened for additional data.

STUDY SELECTION AND DATA EXTRACTION

All articles and abstracts reporting uveitis potentially related to rifabutin were considered for inclusion. Fifty-four cases were identified. Pertinent information from the case reports, as judged by the authors, was selected and synthesized for discussion.

DATA SYNTHESIS

Rifabutin is being prescribed increasingly for the treatment and prophylaxis of Mycobacterium avium complex (MAC) infection in the HIV-infected population. Uveitis was initially thought to be a rare, dose-limited complication of rifabutin therapy. In an early dose-ranging tolerance study, uveitis was associated with daily doses of 1200 mg or more. Because this toxicity appeared to be dose-related, lower dosages (300-600 mg/d) of rifabutin were selected for study in subsequent clinical trials. More recent reports noting the association of uveitis with these lower dosages of rifabutin have raised concerns about the prevalence of this adverse event. In the 54 identified cases, patients presented with symptoms of unilateral or bilateral uveitis from 2 weeks to more than 7 months following initiation of rifabutin therapy. In all reported cases, patients were receiving concurrent therapy with clarithromycin and/or fluconazole, both of which have inhibitory effects on rifabutin metabolism. In most cases, uveitis resolved within 1-2 months following discontinuation of rifabutin with or without administration of topical corticosteroids.

CONCLUSIONS

Rifabutin is prescribed frequently for the prophylaxis and treatment of MAC infection, especially in patients with HIV. Uveitis is a rare, dose-related toxicity of this therapy. The risk of rifabutin-associated uveitis may be increased in patients receiving concurrent therapy with clarithromycin or fluconazole because of drug interactions. Patients receiving therapy with combinations of any of these agents should be warned about signs and symptoms of uveitis and be monitored closely for the development of rifabutin toxicity. If uveitis develops, rifabutin therapy should be discontinued promptly.

Mycobacterium avium complex infection in AIDS: clinical features, treatment, and prevention

Infection with Mycobacterium avium complex (MAC) may cause a serious disseminated bacterial infection in up to 40% of patients with advanced HIV infection. Disseminated MAC has a negative impact on quality of life and contributes significantly to morbidity and mortality. Prompt diagnosis and aggressive treatment can diminish those effects. Disseminated disease can be prevented in many patients with the use of rifabutin prophylaxis. Nurses play an important role in evaluating symptoms and educating patients about the prevention and treatment of disseminated MAC.

Acute uveitis associated with rifabutin use in patients with human immunodeficiency virus infection

PURPOSE

We studied patients with a new anterior uveitis syndrome associated with rifabutin use.

METHODS

Nine patients with the acquired immunodeficiency syndrome (AIDS) who developed acute anterior uveitis were identified retrospectively from institutional ophthalmology, infectious disease, and AIDS primary care practices. Five patients initially had hypopyon; in three patients hypopyon was bilateral and recurrent. The medical history, initial signs and symptoms, diagnostic examination, clinical course, and response to therapy were ascertained by a review of the medical records.

RESULTS

All nine patients were being treated with rifabutin for treatment of, or prophylaxis against, Mycobacterium avium complex. In no patient was another untreated cause of uveitis found. In each patient the uveitis resolved rapidly without sequelae with treatment with topical corticosteroids alone. In eight patients uveitis resolved completely while treatment or prophylaxis for M. avium complex was maintained.

CONCLUSIONS

We studied a new hypopyon uveitis syndrome in patients with AIDS who are being treated with rifabutin. The interaction of multiple drugs may contribute to this uveitis syndrome. This uveitis is remarkable because it is fulminant yet responds rapidly to topical corticosteroids. Characterization of this syndrome is important because hypopyon in the immunocompromised patient generally mandates intensive, and sometimes invasive, ophthalmic and systemic examination and therapy. Additional study is required to determine whether immune status, underlying infection, or drug-related factors contribute to the development of this uveitis syndrome. Although this syndrome remains a diagnosis of exclusion, ophthalmologists must be aware of it, so that intervention is guided appropriately.