Cardiac toxicity of the echinocandins: chance or cause and effect association?

WHAT IS KNOWN AND OBJECTIVE: Fungal infections pose a constant risk to critically ill and immunosuppressed patients. The echinocandin antifungals give practitioners an arsenal of agents with apparently lower toxicity relative to older agents. The objective of this commentary is to review the cardiac toxicity of the echinocandin antifungals in the light of recent evidence and published case reports. COMMENT: Three case reports detail cardiac decompensation following the initiation of anidulafungin and caspofungin and corroborate ex vivo laboratory results, in which rat hearts exposed to anidulafungin and caspofungin had significantly decreased cardiac contractility. Our hypothesized mechanism of toxicity of anidulafungin and caspofungin is mitochondrial toxicity. WHAT IS NEW AND CONCLUSION: The clinical corroboration of the ex vivo work presented above highly suggests that the cardiac toxicity seen with some of the echinocandin antifungals is a cause and effect pattern, not a chance finding.

Voriconazole versus a regimen of amphotericin B followed by fluconazole for candidaemia in non-neutropenic patients: a randomised non-inferiority trial.

BACKGROUND: Voriconazole has proven efficacy against invasive aspergillosis and oesophageal candidiasis. This multicentre, randomised, non-inferiority study compared voriconazole with a regimen of amphotericin B followed by fluconazole for the treatment of candidaemia in non-neutropenic patients. METHODS: Non-neutropenic patients with a positive blood culture for a species of candida and clinical evidence of infection were enrolled. Patients were randomly assigned, in a 2:1 ratio, either voriconazole (n=283) or amphotericin B followed by fluconazole (n=139). The primary efficacy analysis was based on clinical and mycological response 12 weeks after the end of treatment, assessed by an independent data-review committee unaware of treatment assignment. FINDINGS: Of 422 patients randomised, 370 were included in the modified intention-to-treat population. Voriconazole was non-inferior to amphotericin B/fluconazole in the primary efficacy analysis, with successful outcomes in 41% of patients in both treatment groups (95% CI for difference -10.6% to 10.6%). At the last evaluable assessment, outcome was successful in 162 (65%) patients assigned voriconazole and 87 (71%) assigned amphotericin B/fluconazole (p=0.25). Voriconazole cleared blood cultures as quickly as amphotericin B/fluconazole (median time to negative blood culture, 2.0 days). Treatment discontinuations due to all-cause adverse events were more frequent in the voriconazole group, although most discontinuations were due to non-drug-related events and there were significantly fewer serious adverse events and cases of renal toxicity than in the amphotericin B/fluconazole group. INTERPRETATION: Voriconazole was as effective as the regimen of amphotericin B followed by fluconazole in the treatment of candidaemia in non-neutropenic patients, and with fewer toxic effects. RELEVANCE TO PRACTICE: There are several options for treatment of candidaemia in non-neutropenic patients, including amphotericin B, fluconazole, voriconazole, and echinocandins. Voriconazole can be given both as initial intravenous treatment and as an oral stepdown agent.

The contribution of cis-elements to disease-associated repeat instability: clinical and experimental evidence.

Alterations in the length (instability) of gene-specific microsatellites and minisatellites are associated with at least 35 human diseases. This review will discuss the various cis-elements that contribute to repeat instability, primarily through examination of the most abundant disease-associated repetitive element, trinucleotide repeats. For the purpose of this review, we define cis-elements to include the sequence of the repeat units, the length and purity of the repeat tracts, the sequences flanking the repeat, as well as the surrounding epigenetic environment, including DNA methylation and chromatin structure. Gender-, tissue-, developmental- and locus-specific cis-elements in conjunction with trans-factors may facilitate instability through the processes of DNA replication, repair and/or recombination. Here we review the available human data that supports the involvement of cis-elements in repeat instability with limited reference to model systems. In diverse tissues at different developmental times and at specific loci, repetitive elements display variable levels of instability, suggesting vastly different mechanisms may be responsible for repeat instability amongst the disease loci and between various tissues.

Differential transcription factor expression in human mononuclear cells in response to amphotericin B: identification with complementary DNA microarray technology.

STUDY OBJECTIVE: To identify genes differentially expressed in human monocytic cells exposed to amphotericin B in vitro. DESIGN: In vitro experiment. SETTING: Hospital laboratory. MATERIAL: Human mononuclear cell line, THP-1. INTERVENTION: Human mononuclear cells were exposed to amphotericin B or media alone for 6 hours. After exposure, total RNA was isolated and reverse transcribed to complementary DNA. Differences in probe hybridization observed during blotting were measured, and genes with altered regulation were described by using human complementary DNA microarray technology. MEASUREMENTS AND MAIN RESULTS: Of 588 genes represented on the array, 16 transcripts were found to be upregulated and 4 transcripts were downregulated in response to amphotericin B. These findings suggest that amphotericin B alters the expression of genes in human monocytic cells that play a role in many cellular functions, including immune response, signal transduction, and cell differentiation. CONCLUSION: Amphotericin B induces alterations in human cell gene transcription. These changes could be used to evaluate differences in toxicity or efficacy observed in patients receiving this agent.

Intravenous itraconazole.

OBJECTIVE: To review the pharmacology, mycology, chemistry, pharmacokinetics, efficacy, safety, tolerability, dosage, administration, and economic issues of intravenous itraconazole. DATA SOURCES: A MEDLINE search from 1978 to June 2000 of the English-language literature and an extensive review of meeting abstracts was conducted. Due to the paucity of published information concerning the pharmacokinetics, efficacy, and safety of the intravenous formulation of intravenous itraconazole, additional information was obtained from the manufacturer. DATA EXTRACTION: Data from in vitro and preclinical studies, as well as Phase II and III clinical trials, were included. DATA SYNTHESIS: The triazole antifungal agent itraconazole is available in a cyclodextrin-based intravenous formulation. Intravenous itraconazole is indicated for the treatment of pulmonary and extrapulmonary blastomycosis; histoplasmosis, including chronic cavitary pulmonary disease and disseminated, nonmeningeal histoplasmosis; and pulmonary and extrapulmonary aspergillosis in patients who are intolerant of or who are refractory to amphotericin B. This formulation provides quicker and more consistent therapeutic concentrations than the oral formulations. Clinical data comparing the efficacy of intravenous itraconazole with that of amphotericin B are lacking. CONCLUSIONS: Intravenous itraconazole offers a less toxic alternative for patients with pulmonary and extrapulmonary blastomycosis, histoplasmosis, and aspergillosis who cannot receive oral medications or who are intolerant of or refractory to amphotericin B.

Amphotericin B induces expression of genes encoding chemokines and cell adhesion molecules in the human monocytic cell line THP-1.

Amphotericin B is known to elicit immunomodulatory effects on neutrophil, monocyte, and lymphocyte function. It also has been shown to induce the release of proinflammatory cytokines from human monocytes and macrophages. Release of these cytokines has been associated with the infusion-related toxicity observed after administration of this drug. The present study demonstrates that amphotericin B increases mRNA for the chemokines interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1, and macrophage inflammatory protein (MIP)-1beta, as well as the cell adhesion molecules intercellular adhesion molecule (ICAM)-1 and CD44 in the human monocytic cell line THP-1. Amphotericin B increased the concentrations of IL-8, MCP-1, and MIP-1beta in a dose-dependent fashion. Amphotericin B also induced expression of ICAM-1 but not CD44 in these cells. Production of these proteins in response to amphotericin B may play a role in the immunomodulatory activity and toxicity of this antifungal agent.

Nucleotides of the tRNA D-stem that play an important role in nuclear-tRNA export in Saccharomyces cerevisiae.

Nuclear export of tRNA in Saccharomyces cerevisiae involves Los1p and Arc1p. Los1p facilitates tRNA translocation across the nuclear pore complex whereas Arc1p plays a role in delivering some species of tRNA exiting the nucleus to their cognate aminoacyl-tRNA synthetases. Here, we show that mutations of C11 and G24 of the D-stem of the yeast tyrosine amber-suppressor tRNA have different effects on nuclear export of the tRNA. Changing G24 had no effect on export of the tRNA to the cytoplasm. In contrast, mutating C11 resulted in nuclear retention of the tRNA. Nuclear retention of the tRNA mutants was not due to lack of processing, since only the mature forms of the tRNA mutants were found. The fact that mutations of G24 did not affect export of the tRNA also indicates that the effect of mutating C11 is not due to gross alteration of the tertiary structure resulting from disruption of the C11/G24 base pair. Expression of Los1p and the mammalian tRNA export receptor exportin-t rescued nuclear export of the tRNA with changes at position 11. The export-defective mutations of the tRNA mutants were suppressed by introducing the complementary nucleotides at position 24. Taken together, these findings suggest that C11 is important for binding of the tRNA to the export receptor, and that this binding is influenced by the conformation of the base. Finally, the export-defective tRNA mutants described can be used as reporters to identify eukaryotic proteins involved in the nuclear-tRNA export process, and characterize the molecular interactions between known receptors and the tRNA substrate.

Use of intravaginal microbicides to prevent acquisition of Trichomonas vaginalis infection in Lactobacillus-pretreated, estrogenized young mice.

D2A21, a novel peptide antibiotic has in vitro activity against a wide spectrum of sexually transmitted diseases (STD). In this study we tested the hypothesis that intravaginal D2A21 would interfere with acquisition of Trichomonas vaginalis infection in a modified mouse model. T. vaginalis infections of estrogenized young mice pretreated with Lactobacillus vaginalis or Lactobacillus rhamnosus were more frequent and persistent than those in mice pre-treated with Lactobacillus gasseri or Lactobacillus acidophilus. One hundred percent T. vaginalis infection was achieved for 2-4 days post-challenge when intravaginal L. rhamnosus pre-treatments were given to estrogenized mice 48 hr prior to a single T. vaginalis challenge. Estrogenized mice pre-treated with L. rhamnosus were pre-medicated with intravaginal placebo gel, 0.5% or 2% D2A21 gel, or 500 microg/mL metronidazole gel prior to T. vaginalis challenge. Both 2% D2A21 and metronidazole gels were significantly more efficacious (10% or none infected) than placebo gel (53% infected) in preventing vaginal T. vaginalis infections in mice.

Molecular typing of Trichomonas vaginalis isolates by HSP70 restriction fragment length polymorphism.

Subtyping isolates of Trichomonas vaginalis is an essential tool for understanding the epidemiology of this common sexually-transmitted disease. Restriction fragment length polymorphism (RFLP) analysis employing a probe from the heat-inducible cytoplasmic HSP70 gene family hybridized with EcoR I-digested genomic DNA was used in the molecular typing of Trichomonas isolates. Analysis of five American Type Culture Collection (ATCC) reference strains and 31 Jackson, Mississippi, isolates from six male and 21 female patients, revealed 10 distinct RFLP pattern subtypes of Trichomonas. The subtypes were temporally stable and cosmopolitan. The RFLP profiles seen in Maryland, Ohio, Massachusetts, and New York ATCC strains were identical to those of some Mississippi isolates, even though the samples were isolated 10-35 years apart. There was no correlation between metronidazole resistance and RFLP subtype with resistant isolates from eight patients distributed among six different subtypes.

Administration of crushed extended-release pentoxifylline tablets: bioavailability and adverse effects.

The pharmacokinetics of crushed and intact pentoxifylline tablets were compared, and the frequency of adverse effects was evaluated. Intact 400-mg extended-release pentoxifylline tablets, crushed 400-mg tablets, intact 600-mg tablets, and crushed 600-mg tablets were given sequentially to 10 healthy male volunteers. Blood samples were collected at time 0, at 30-minute intervals for the first three hours, and at 4, 6, 8, 12, and 24 hours after the dose and analyzed by capillary gas chromatography for pentoxifylline and three major metabolites. The bioavailability of the crushed tablets relative to the intact tablets was 156% for the 400-mg strength and 137% for the 600-mg strength. The area under the plasma drug concentration-time curve from 0 to 24 hours (AUC0-24) for the 400-mg tablets (crushed and intact) differed significantly from that for the 600-mg tablets; there was no significant difference between intact 400-mg and intact 600-mg tablets or crushed 400-mg and crushed 600-mg tablets. The maximum plasma drug concentration (Cmax) was significantly greater and the time to maximum concentration (t(max)) significantly shorter for crushed tablets than intact tablets. The 400-mg crushed tablet caused mild nausea in three subjects. The 600-mg crushed tablet caused both moderate nausea and dizziness in seven subjects and diaphoresis, headache, and vomiting in one subject each. Cmax was higher and tmax shorter when pentoxifylline tablets were administered crushed rather than intact, and the increase in maximum plasma concentrations appeared to cause dose-related adverse effects; crushing the tablets did not decrease the relative bioavailability.

Amphotericin B-induced interleukin-1beta expression in human monocytic cells is calcium and calmodulin dependent.

Amphotericin B remains the agent of choice for treatment of severe fungal infections. Its use is hindered by adverse effects, including infusion-related fever, chills, and hypotension, as well as nephrotoxicity with secondary anemia, hypokalemia, and hypomagnesemia. Amphotericin B-induced transcription and expression of interleukin (IL)-1beta by human monocytes is believed to be involved in mediating infusion-related adverse effects. It is shown here that agents that increase intracellular calcium [Ca++]i (A23187 and thapsigargin) in human monocytic cells also induce IL-1beta expression. Furthermore, amphotericin B-induced IL-1beta expression is attenuated by the calmodulin antagonist calmidazolium. Amphotericin B 5.41 microM increases [Ca++]i by up to 300 nM in these cells. In the presence of a nominal calcium buffer or EGTA, amphotericin B-induced IL-1beta expression is attenuated. Thus, amphotericin B acts as an ionophore to increase [Ca++]i and activates calmodulin-mediated expression of IL-1beta in human monocytes.

Antiinfectives update: focus on treatment and prevention of viral and associated infections.

OBJECTIVE: To review the clinically significant antiinfectives approved by the Food and Drug Administration (FDA) since 1996, with an emphasis on agents used for treatment, prevention, or suppression of infection in immunocompromised individuals. DATA SOURCES: A MEDLINE search covering November 1994 to March 1998 was conducted to identify all antiinfectives (new medications and old medications with new indications) and the pertinent literature for review. The search was updated in August 1998 and supplemented with an FDA listing of approved drugs to enhance completeness. STUDY SELECTION: Clinically relevant studies were selected to highlight specific points about each medication. Preclinical publications were used when sufficient information was not available from clinical trials and this information was needed for clinical practice. CONCLUSIONS: Several new and promising antiretroviral agents (stavudine, lamivudine, saquinavir soft-gel capsules, nelfinavir, efavirenz) have been approved, which may allow more options to control HIV viremia. New options for treatment, prevention, and suppression of infections in immunocompromised individuals include azithromycin, cidofovir, famciclovir, valacyclovir, and itraconazole suspension. Liposomal-based amphotericin products may be associated with less toxicity than conventional amphotericin B; however, superior efficacy has not been proven.

Antifungal therapy during pregnancy.

Careful consideration of the benefit to the mother and the risk to the fetus is required when prescribing antifungal therapy in pregnancy. Imidazoles are considered safe as topical therapy for fungal skin infections during pregnancy. Nystatin is minimally absorbed and is effective for vaginal therapy. Although vaginal use of the imidazoles is probably safe during the later stages of pregnancy, their systemic absorption is higher than when applied to the skin. The systemic antifungal drug with which there has been the most experience in pregnancy is amphotericin B. There have been no reports of teratogenesis attributed to this agent. There is evidence to suggest that fluconazole exhibits dose-dependent teratogenic effects; however, it appears to be safe at lower doses (150 mg/day). Ketoconazole, flucytosine, and griseofulvin have been shown to be teratogenic and/or embryotoxic in animals. Iodides have been associated with congenital goiter and should not be used during pregnancy.

Amphotericin B activation of human genes encoding for cytokines.

Amphotericin B has been shown to cause release of cytokines, including interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), from monocytes and macrophages. Human and murine monocytic cell lines were used to evaluate the effects of amphotericin B on the transcription of IL-1alpha, IL-1beta, and TNF-alpha and the transcription and production of soluble IL-1 receptor antagonist (sIL-1Ra). The effects of inhibitors of transcription and translation on amphotericin B-induced IL-1beta expression in a human monocytic cell line were also evaluated. Amphotericin B markedly increased IL-1beta and TNF-alpha mRNA levels, with peak levels occurring by 4 h. Amphotericin B induced production of sIL-1Ra in a dose-dependent fashion and induced sIL-1Ra mRNA, with peak levels at 24 h. Cycloheximide and actinomycin D resulted in a dose-dependent decrease in amphotericin B-induced IL-1beta expression at 2 h. Thus, amphotericin B induces gene expression for IL-1beta, TNF-alpha, and IL-1Ra in human and murine monocytic cells.

Amphotericin B enzyme-linked immunoassay for clinical use: comparison with bioassay and HPLC.

OBJECTIVE: To evaluate a new enzyme-linked immunosorbent assay (ELISA) for amphotericin B in serum samples. Results are compared with those obtained by HPLC and bioassay. DESIGN: Comparison of results obtained by ELISA, HPLC, and bioassay. METHODS: We developed a new ELISA using a polyclonal rabbit antibody to measure serum amphotericin B concentrations. Blinded samples of amphotericin B in concentrations of 0.15-78 micrograms/mL were prepared in human serum and assayed simultaneously by the ELISA, HPLC, and bioassay. The results of each assay were derived from standard curves and evaluated by using the Table Curve 2D computer program. These data were compared by using correlation analysis with evaluation of Pearson's correlation coefficient by Student's t-test. RESULTS: ELISA and bioassay compared favorably at amphotericin B concentrations of 0.3-20 micrograms/mL with a correlation coefficient of r = 0.993, while ELISA and HPLC compared with a correlation coefficient of r = 0.944. The average coefficient of variation over the range 0.3-20.0 micrograms/mL was 28% +/- 7% for HPLC, 26% +/- 9% for ELISA, and 13% +/- 4% for bioassay. Comparison of all three assays revealed the highest correlation with the ELISA assay (r = 0.998) for the range of concentrations (0.3-20 micrograms/mL) routinely achieved. Samples containing concentrations in excess of 20 micrograms/mL could be diluted. Desiccation for concentrations less than 0.3 microgram/mL was not tested. CONCLUSION: The determination of serum amphotericin B concentrations by ELISA gave results similar to those obtained by a bioassay and HPLC technique. Although variability appears greater with ELISA, the ease of performing yjis assay expedites the evaluation of amphotericin B concentrations from lipid formulations without interference from coadministered antibacterials of azole antifungals.

Amphotericin B enzyme-linked immunosorbent assay.

Our purpose was to develop and characterize an enzyme-linked immunosorbent assay (ELISA) which could measure the concentration of amphotericin B in serum. Amphotericin B was assayed by competition ELISA. Multiwell ELISA plates coated with amphotericin B (1.0 micrograms/ml) conjugated to bovine serum albumin were used to test replicates of serum samples spiked with amphotericin B. Purified rabbit polyclonal antibody against amphotericin B (1.4 micrograms/ml) was added subsequent to the instillation of samples spiked with unknown amounts of amphotericin B. Experiments were performed to test the sensitivity, specificity, precision, and accuracy of the assay. The ability to measure lipid-associated amphotericin B was also evaluated in preliminary studies. Analysis of reference samples containing amphotericin B yielded a traditional sigmoidal curve. The limits of detection were 0.15 to 156 micrograms/ml. The sensitivity of the assay was affected by light and temperature exposure. Assay specificity was altered only by the presence of nystatin, a polyene antifungal agent similar to amphotericin B. Intrarun (coefficient of variation = 3.0%) and interrun (coefficient of variation = 12.8%) coefficients of variation were calculated and were comparable to those in similar assays. The assay's correlation coefficient (r = 0.907) demonstrated a statistically significant correlation between the optical density of the sample and the concentration of drug in the sample. The amphotericin B ELISA's ease, precision, and overall accuracy suggest that this assay could be used for assessments of serum amphotericin B concentrations. Multiple research questions concerning the role of serum amphotericin B concentrations in toxicity and efficacy have gone unanswered because of the labor-intensive nature of the assays which have been available to date. The ability to easily and rapidly measure 40 duplicate samples containing amphotericin B should also prove to be a distinct advantage for clinical research or reference laboratories in addressing these questions.