Activity of fluconazole (UK 49,858) and ketoconazole against Candida albicans in vitro and in vivo

Successful treatment of Candida osteomyelitis with fluconazole. A noncomparative study of two patients

We describe two patients with osteomyelitis due to Candida spp. treated with fluconazole, a new triazole antifungal. One patient had extensive involvement of ribs and costochondral regions of the anterior chest, and the other had vertebral infection. Both were cured with courses of 10 and 14 months, with greater than or equal to 1 year of follow-up after fluconazole was discontinued. Fluconazole is an attractive agent for the treatment of Candida osteomyelitis and deserves to be studied more extensively for this indication.

Collaborative investigation of variables in susceptibility testing of yeasts

A multicenter study was performed to evaluate the effect of medium, incubation time (24 and 48 h), and temperature (30 and 35 degrees C) on intra- and interlaboratory variations in MICs of flucytosine, amphotericin B, and ketoconazole for yeasts. Testing was performed on coded isolates of Candida species (11 strains) and Cryptococcus neoformans (2 strains) by using a standard macrodilution protocol 11 laboratories. Four chemically defined media buffered to pH 7.0 with morpholinepropanesulfonic acid were evaluated, including buffered yeast nitrogen base, synthetic amino acid medium-fungal, RPMI 1640 medium, and high-resolution antifungal assay medium. Intralaboratory variability was less than or equal to fourfold for 97% of the replicate sets of data. The highest level of interlaboratory agreement, irrespective of antifungal agent or incubation conditions, was observed with RPMI 1640 medium. Intralaboratory variability was less than or equal to fourfold for 93% of the determinations with ketoconazole and 100% with flucytosine tested in RPMI 1640 medium at 35 degrees C for 24 h. Variability in amphotericin B results was less than or equal to fourfold for 81% of the determinations in RPMI 1640 medium at 35 degrees C for 48 h. The rank order of MICs within each antifungal test group was similar among the various laboratories and was generally in agreement with the reference rank order regardless of the test medium that we used.

Fluconazole: a new triazole antifungal agent

Fluconazole is a fluorine-substituted, bis-triazole antifungal agent. Its mechanism of action, like that of other azoles, involves interruption of the conversion of lanosterol to ergosterol via binding to fungal cytochrome P-450 and subsequent disruption of fungal membranes. Activity against Aspergillus spp., Blastomyces dermatitidis, Candida spp., Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum, and Paracoccidioides brasiliensis has been demonstrated in several animal models. Fluconazole can be administered both orally and intravenously. Mean peak serum concentrations achieved in human volunteers after 50 and 100 mg (oral) are 3.1 and 7.0 mumols/L respectively. Protein binding is low (11 percent) and cerebrospinal fluid to serum ratio is 0.58 to 0.89. Serum half-life is long (22-32 hours) and elimination is via renal clearance of unchanged drug. Clinical trials and reports support the use of fluconazole in treatment of candidiasis, particularly oropharyngeal and esophageal infections in immunocompromised hosts. Fluconazole is also approved for initial and suppressive therapy of cryptococcal meningitis. Its role in management of systemic fungal infections will be further defined once results of other comparative trials become available. Fluconazole is well tolerated and its effects on steroidogenesis are markedly less than those of ketoconazole. Antipyrine clearance is not altered at low doses (50 mg) of fluconazole; however, drug interactions with the use of larger doses can be anticipated with agents such as cyclosporin, phenytoin, oral hypoglycemics, and warfarin. Rifampin appears to decrease metabolic clearance of fluconazole. Fluconazole is available as oral and parenteral formulations. Once-daily doses of 100-400 mg are recommended. Dosage reduction is advised for patients with impaired renal function.

Fluconazole. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in superficial and systemic mycoses

Fluconazole is a bis-triazole antifungal drug with novel pharmacokinetic properties (metabolic stability, relatively high water solubility) which contribute to its therapeutic activity. Clinical experience is limited to a relatively small number of mycoses and, as might be expected at this early stage of development, optimal dosage and duration of treatment for some serious mycoses is not yet established. Further study to evaluate higher dosages and to establish the efficacy of fluconazole relative to more established antifungal agents is required. In patients with oropharyngeal or oesophageal candidiasis, fluconazole produces rapid relief and eradicates the yeast in 50 to 90% of patients. Relapse of oral infection is common in chronically immunocompromised patients regardless of the antifungal used, and adequate primary therapy plus long term prophylaxis appears necessary in patients with AIDS. A single oral dose of fluconazole was comparable to standard topical azole therapy in women with acute vaginal candidiasis. Preliminary reports of success against deep-seated candidiasis are encouraging; moreover, experience in noncomparative clinical trials suggests that fluconazole 200 to 400mg once daily resolves infection in the majority of seriously ill patients. Clinical improvement has been reported in a few cases of pulmonary Aspergillus infection but the overall efficacy of conventional dosages of fluconazole in this mycosis has not been as impressive. Early experience in coccidioidosis, predominantly meningitis, suggests a beneficial clinical effect with oral fluconazole in this difficult to treat mycosis but relapse remains a problem. Fluconazole is a promising treatment of cryptococcal meningitis. The rate of clinical resolution and eradication of Cryptococcus neoformans from cerebrospinal fluid has been similar between fluconazole and amphotericin B treatment groups in comparative trials. Comparative trials of maintenance therapy indicate a similar low rate of relapse among patients given oral fluconazole once daily and intravenous amphotericin B once weekly. However, these results are preliminary and further study is required. Fluconazole has been well tolerated to date but wider clinical experience is needed, especially with regard to the rate occurrence of hepatotoxicity and exfoliative skin reactions. The promising clinical response of patients with various forms of candidiasis or cryptococcosis--together with convenient administration regimens--recommends fluconazole as a useful addition to currently available systemic antifungal therapies, in particular for the treatment of mycoses in patients with AIDS.

In vitro and in vivo activities of Sch 39304, fluconazole, and amphotericin B against Histoplasma capsulatum

The antifungal activities of amphotericin B and two triazoles, Sch 39304 and fluconazole, were tested against Histoplasma capsulatum. In this study Sch 39304 compared favorably with amphotericin B in treating histoplasmosis in normal and leukopenic mice, whereas fluconazole was much less active. The differences in the efficacies of the triazoles appeared to be due to differences in their pharmacokinetics and the dosage schedule that was used. For amphotericin B there was a good correlation between in vitro and in vivo efficacy, but this was not true of the triazole derivatives. These results further demonstrate that, with the methods used in this study, in vitro susceptibility testing of triazoles may not be predictive of in vivo activity against isolates of H. capsulatum.

New antifungal agents for the systemic mycoses

The azoles are the prominent broad spectrum oral antifungal agents in use or under clinical investigation for the systemic mycoses. This class of antifungal agents is represented by the marketed drug ketoconazole (Nizoral) and the experimental triazoles furthest along in clinical trials in the United States, itraconazole and fluconazole. Ketoconazole use is limited by its side effect profile and activity spectrum. Itraconazole appears to be better tolerated and less toxic to liver function, does not cause adrenal suppression and is more active against Aspergillus and Sporothrix schenckii. Fluconazole appears to be a highly promising agent due its highly favorable pharmacokinetic profile; it is water soluble, is well tolerated, is not metabolized to inactive constituents, it has a long half-life and, unlike the other azoles, high cerebrospinal fluid levels are readily attained for consideration in meningeal mycoses. It remains to be determined what place these new triazoles have in managing immunosuppressed patients including those with acquired immune deficiency syndrome known as AIDS. Other experimental antifungal agents, including ambruticin, amphotericin B methyl ester and saramycetin are also described. Sales figures are presented of drugs marketed in the United States for the systemic mycoses and reflect the growing problem of fungal diseases in the population.

Orally administered antifungal therapy for experimental keratomycosis

Fluconazole, an experimental azole antifungal agent with good tissue penetration following oral administration, offers the possibility of a new approach to the treatment of keratomycosis. Its efficacy as an orally administered agent was investigated in two models of experimental fungal infection in Dutch-belted rabbits. The study proceeded in three stages. In the first, a model of keratitis due to Aspergillus fumigatus was developed, the suitability of quantitative isolate recovery techniques for the evaluation of the disease caused by this organism was confirmed, and the correlation between the severity of clinical disease scored nonparametrically and the isolate recovery rate was established. The model was found to be most useful for study during the first 5 days of infection. The natural course of experimental Candida alibcans keratitis was evaluated and, on the basis of quantitative isolate recovery techniques, this model was found to be appropriate for studies lasting up to 1 week. In the second stage, corneal uptake following oral administration of fluconazole was studied in Dutch-belted rabbits. The drug was found to readily penetrate the cornea in amounts that correlated with serum levels (R = 0.89). Eight hours following a single 20 mg/kg dose, the corneal level was 7.4 mg/gm, almost double the amount when a 10 mg/kg dose was administered. When given in a twice daily divided dose, fluconazole accumulated steadily in the corneas over a period of 5 days. The presence of inflammation induced by fungal infection did not influence corneal uptake. In the final stage, the efficacy of orally administered fluconazole in the treatment of keratomycosis was evaluated. Overall, a significant therapeutic effect was observed with both infections. Treatment of the animals with oral fluconazole for 1 day prior to inoculation with Candida albicans led to a significant decrease in isolate recovery 1 day later (P = 0.01). However, when treatment was continued for 5 days following inoculation, no additive effect of pretreatment was noted. Pretreatment for 1 day followed by 5 days postinoculation treatment led to a significant decrease in clinical disease (P less than 0.05) and isolate recovery (P = 0.05). A beneficial effect of pretreatment compared to treatment begun 1 day postinoculation, as measured by a reduction in clinical severity and isolate recovery, was also noted. On the basis of these short-term therapeutic studies and the excellent corneal penetration of fluconazole, further investigation of oral therapy of keratomycosis appears warranted.

Comparison of fluconazole and SDZ89-485 for therapy of experimental murine coccidioidomycosis

We infected mice with arthroconidia of Coccidioides immitis by intraperitoneal injection and 48 h later treated them with either oral fluconazole or SDZ89-485, a new triazole. Both drugs completely inhibited fungal growth when administered at a dose of 50 mg/kg of body weight twice a day, but only SDZ89-485 was fully inhibitory at a dose of 5 mg/kg twice a day. In a second experiment, treatment with SDZ89-485 was delayed until 8 days after infection to allow infection to be well established before treatment. Both 5 and 50 mg/kg twice a day were effective regimens, which establishes that SDZ89-485 has activity against spherules in vivo. Mice that received fluconazole (50 mg/kg twice a day) had a peak level in blood of 60 micrograms/ml 1 h after a dose, but no measurable amount was found after 12 h. SDZ89-485 was more slowly absorbed, reaching a peak level in blood of 14 micrograms/ml at 12 to 15 h after a dose of 50 mg/kg. We conclude that SDZ89-485 is more effective than fluconazole as treatment for experimental systemic coccidioidomycosis in mice, even though fluconazole achieves higher peak levels in blood.

Fungispecificity of fluconazole against Candida albicans

Candida albicans is an opportunistic pathogen of human mucosal surfaces. Colonization of oral and vaginal mucosa by this yeast is antagonized by the resident normal bacterial population. However, antibacterial therapy can alter the normal flora to allow fungal cells to attach, grow and invade host tissues. We studied the antimicrobic activity of fluconazole against clinical isolates of oral and vaginal bacteria and Candida albicans in vitro and in vivo by scanning and transmission electron microscopy; we also compared the bactericidal activity of fluconazole with clotrimazole in vitro by microbiologic assay. Fluconazole lysed fungi but did not change the ultrastructure of bacteria. Clotrimazole, but not fluconazole, was bactericidal against lactobacillus and streptococcus, the principal species of the oral and vaginal cavities. We conclude that Candida albicans, but not oral and vaginal bacteria, is susceptible to fluconazole. These observations help explain the antimycotic specificity of fluconazole and its efficacy against candidiasis in humans.

Comparison of in vivo activity of fluconazole with that of amphotericin B against Candida tropicalis, Candida glabrata, and Candida krusei

Fluconazole (UK-49,858) is a new oral bis-triazole antifungal agent with demonstrated activity against Candida albicans. Because of the increasing importance of infections due to other species of Candida, we studied the efficacy of fluconazole in a rat model of established systemic candidiasis, using clinical isolates of C. tropicalis, C. glabrata, and C. Krusei. In normal rats, oral fluconazole at both 20 and 80 mg/kg per day for 7 days reduced both kidney and liver titers of C. tropicalis and C. glabrata compared with those in control animals and was only slightly inferior to amphotericin B. Both fluconazole and amphotericin B were ineffective in reducing kidney titers of C. krusei, but amphotericin B was more effective than fluconazole in reducing liver titers. Fluconazole showed no increased efficacy at the higher dose of 80 mg/kg per day compared with 20 mg/kg per day in any experiment. These results suggest that oral fluconazole may be useful in the treatment of established disseminated candidiasis caused by species other than C. albicans. Further in vivo studies are needed, however, to define minimum effective doses and length of therapy and to test additional Candida isolates.

In vitro susceptibilities of yeasts to a new antifungal triazole, SCH 39304: effects of test conditions and relation to in vivo efficacy

We used six candidal strains (two Candida albicans and one each of four other species) to study the effects of test conditions on the activity of SCH 39304 compared with that of fluconazole in broth macro- and microdilution assays. Increasing the inoculum from 10(2) to 10(5) yeasts per ml raised the MICs for all isolates up to greater than 512-fold. In contrast, results with a 50% turbidimetric endpoint (50% inhibitory concentration; IC1/2) varied no more than twofold. Similar effects were seen with fluconazole, and both drugs were found to have an associated delay in onset of action. Acidity was found to increase both MICs and IC1/2s. Other effects were observed among four synthetic media, but a consistent pattern was not identified. Incubation temperatures of 37, 35, and 30 degrees C yielded equivalent results. Broth microdilution IC1/2s against most of 40 isolates of C. albicans were 0.31 microgram/ml +/- fourfold for SCH 39304 and 0.16 microgram/ml +/- twofold for fluconazole. Treatment of experimental candidiasis in rats with SCH 39304 and fluconazole resulted in 50% effective doses of 0.33 and 0.49 mg/kg per day, respectively. In contrast, another C. albicans isolate, previously identified as resistant to other azoles, had IC1/2s of 20 micrograms of SCH 39304 per ml and, in vivo, a 50% effective dose of 2.25 mg/kg per day. We conclude that the in vivo efficacy of SCH 39304 correlates with MIC results when broth macrodilution testing is performed with a small inoculum and with IC1/2 results which are independent of inoculum size.

Fluconazole (UK-49,858) treatment of candidiasis in normal and diabetic rats

Fluconazole (UK-49,858), a new oral bistriazole antifungal agent, was compared with amphotericin B in the treatment of established systemic infection with Candida albicans in normal and diabetic rats. In normal rats, oral fluconazole at 10 mg/kg per day for 7 days reduced Candida colony counts in the kidneys and livers as well as amphotericin B did and was nearly as effective as amphotericin B in a 21-day treatment trial. There was no further reduction in Candida colony counts when normal rats were treated with fluconazole at 40 mg/kg twice a day for 7 days. In streptozotocin-induced diabetic rats, fluconazole at 20 mg/kg per day for either 7 or 21 days compared favorably with amphotericin B in efficacy. Results of our study suggest that oral fluconazole may be useful in the treatment of established disseminated candidiasis in normal as well as diabetic hosts.

Selection of orally active antifungal agents from 3,5-substituted isoxazolidine derivatives based on acute efficacy-safety profiles

Routine in vitro screening of a new synthetic series of 3,5-substituted 2-methylisoxazolidines revealed that three imidazole analogs (PR 967-248, PR 967-234, and PR 969-566) and, to a lesser extent, a triazole analog (PR 988-399) exerted rather potent antifungal activity against three systemic and four dermatophytic classes of fungi. When tested in vivo for ability to eradicate Candida vaginitis in the rat, the triazole derivative, PR 988-399, was effective after oral administration. In this in vivo test for efficacy, PR 967-234 and PR 969-566 reduced but did not eradicate the infection, while PR 967-248 was inactive. PR 988-399 was, moreover, 4- to 13-fold less potent than the three imidazoles in inhibiting testosterone synthesis in isolated rat Leydig cells. After oral or intravenous administration, PR 988-399 and PR 969-566 elicited the fewest cardiovascular and behavioural side effects in conscious dogs. The rat safety study consisted of oral dosing followed by evaluation of the exploratory motor activity of the naive animals in a novel environment. Motor activity was suppressed least by PR 988-399 and most by PR 969-566. In a battery of mouse behavioural-neuromuscular-drug interaction tests, PR 988-399 and PR 969-566 produced the fewest central-behavioural-neuromuscular signs. These efficacy-safety evaluations were performed with ketoconazole as a positive reference standard. The sequence of drug testing with respect to efficacy-safety considerations appears to be a suitable approach for early detection of orally active antifungal agents such as PR 988-399 for more advanced development.

pH and other effects on the antifungal activity of cilofungin (LY121019)

We investigated the effects of various test conditions on broth macro- and microdilution susceptibility test results for several species of yeasts with a new antifungal agent, cilofungin. As the pH decreased from 7.4 to 3.0, 50% inhibitory concentrations (IC1/2) increased up to 64-fold. This effect was unrelated to yeast growth rate, solvent concentration, or choice of buffer. Broth microdilution results for 42 Candida albicans isolates at pH 7.4 in synthetic amino acid medium, fungal (SAAMF), showed IC1/2 results from 0.08 to 2.5 micrograms/ml, whereas at pH 3.0 the results were 5.0 or 10.0 micrograms/ml. Fungicidal concentrations were closer to MIC results at the lower pH, i.e., an average of 16-fold above the MIC at pH 3.0, compared with an average 256-fold difference at pH 7.4. Two strains that had very different IC1/2 results at pH 7.4 and identical IC1/2 results at pH 3.0 were found to be equally susceptible to cilofungin therapy in rats. In additional studies, other medium effects were demonstrable, with yeast nitrogen broth and minimal essential medium generally yielding higher results than two other synthetic media (SAAMF and RPMI 1640 medium). However, susceptibility results did not change with inoculum between 10(2) and 10(5) yeast cells per ml or temperature between 30 and 37 degrees C. These studies indicate that pH is an important influence on in vitro rank order susceptibility of pathogenic yeasts to cilofungin.

Comparison of fluconazole and ketoconazole for oropharyngeal candidiasis in AIDS

In a randomised, double-blind study the efficacy and toxicity of oral fluconazole 50 mg daily and ketoconazole 200 mg daily were compared for the treatment of oropharyngeal candidiasis in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC). 20 episodes (18 patients) were treated with fluconazole and 20 episodes (19 patients) with ketoconazole. Pretreatment clinical features and laboratory test results were similar in both groups. 17 episodes (85%) in the fluconazole group and 16 (80%) in the ketoconazole group could be evaluated. There was clinical cure at the end of therapy in all fluconazole-treated and 12 of 16 (75%) ketoconazole-treated episodes. Cultures were negative at the end of therapy in 87% of the fluconazole group and 69% of the ketoconazole group. 1 patients stopped taking fluconazole because of severe nausea. 1 of 18 fluconazole-treated and 4 of 19 ketoconazole-treated patients had transient rises in alanine or aspartate aminotransferase. Fluconazole seemed more effective than ketoconazole in the treatment of oral thrush among AIDS and ARC patients.

Comparison of the efficacies of amphotericin B, fluconazole, and itraconazole against a systemic Candida albicans infection in normal and neutropenic mice

We compared the efficacies of the new triazole antifungal drugs fluconazole and itraconazole with that of amphotericin B in vitro and in an animal model of systemic candidiasis in normal and neutropenic mice. Antifungal treatment with fluconazole (2.5 to 20 mg/kg orally twice daily), itraconazole (10 to 40 mg/kg orally twice daily), or amphotericin B (0.1 to 4 mg/kg intraperitoneally once daily) was started 1 day after intravenous injection of 10(4) Candida albicans into normal mice or 10(3) C. albicans into neutropenic mice; the drugs were administered for 2 days. In normal mice the efficacy of treatment, which was assessed on the basis of the number of C. albicans cultured from the kidney, was greater for amphotericin B than for the triazoles. Fluconazole was more potent than itraconazole on the basis of equivalent doses, although itraconazole was more potent on the basis of the amount of free drug that was available. In neutropenic mice amphotericin B was less effective than it was in normal mice, whereas the triazoles were equally effective in normal and neutropenic mice. This was not expected, since in vitro data showed that amphotericin B was highly fungicidal, whereas both fluconazole and itraconazole had only a minimal effect on the growth of C. albicans in vitro.

Fluconazole in the treatment of Candida-associated denture stomatitis

A double-blind trial was carried out to study the effect of oral administration of fluconazole in the treatment of Candida-associated denture stomatitis. The study group consisted of 38 denture stomatitis patients who harbored yeasts, predominantly Candida spp., in significant numbers as determined by culture from the lesions. Half of the patients received 50 mg of fluconazole per day orally for 14 days, and the other half received placebo capsules. The following parameters were studied: degree of palatal erythema, presence of yeast cells (by plate count and microscopy of smears), identification to the species level of dominant yeast organisms, biotyping of Candida albicans, and treatment-related side effects. A significant reduction of erythema was seen after treatment with fluconazole, but the inflammation showed partial relapse 2 to 4 weeks after treatment was terminated. Reduced soreness of the oral mucosa was reported by six of the patients in the fluconazole group. No significant clinical or yeast flora changes were observed in the placebo group. Extensive changes in the yeast flora were observed in the fluconazole group, both in quantity and in composition of yeast species and C. albicans strains (biotypes), which perhaps indicated differences in pathogenicity and fluconazole susceptibility among various yeast species and C. albicans strains. Fluconazole did not produce any changes in the results of blood and urine analyses. The results indicate that fluconazole is a safe and well-tolerated antimycotic drug. The transient clinical and antimycotic effect may have been due in part to the possibility that therapeutic concentrations of the drug were not reached beneath the fitting denture surface and within the denture plaque.

Effects of two oral antimycotics, ketoconazole and fluconazole, upon steroidogenesis in rat adrenal cells in vitro

Rat adrenal cells were incubated with various concentrations of two orally active azole antimycotics in order to evaluate the effects on steroidogenesis. The first compound was ketoconazole, a well-known inhibitor not only of fungal cytochrome P-450 but at higher concentrations also of mammalian cytochrome P-450 dependent enzymes. The second was fluconazole, a newly developed oral antimycotic with a triazole structure, which likewise inhibits fungal cytochrome P-450. The influence of both drugs on mammalian cytochrome P-450 dependent enzymes was investigated in this study. Ketoconazole inhibited ACTH-stimulated corticosterone (IC50 = 0.9 microM) and aldosterone secretion (IC50 = 1.4 microM) and enhanced 11-deoxycorticosterone output at low concentrations but reduced it at higher concentrations. Radiotracer experiments with [3H]pregnenolone or [3H]11-deoxycorticosterone as exogenous substrates revealed a 50% inhibition of the oxidative substrate metabolism at about 1 microM ketoconazole. These effects could also be observed with fluconazole but occurred at concentrations approximately two orders of magnitude higher as compared to ketoconazole. We conclude that fluconazole has a much higher selectivity for fungal cytochrome P-450 than ketoconazole. The order of sensitivity of the cytochrome P-450 dependent enzymes of rat adrenal steroidogenesis to ketoconazole was the 11 beta/18-hydroxylase, the cholesterol side chain cleavage enzyme and the 21-hydroxylase with decreasing sensitivities.

Determination of fluconazole in biological fluids by capillary column gas chromatography with a nitrogen detector

Fluconazole concentrations in biological fluids were determined by high-performance gas chromatography. A simple extraction procedure with chloroform, under basic conditions and after the addition of UK-47,265 as the internal standard and with no evaporation stage, was carried out prior to analysis. A solid injector and a 15-m capillary column, coated with a nonpolar phase and connected to a nitrogen-selective detector that afforded an excellent selectivity and sensitivity, constituted the gas chromatographic system. The duration of each analysis was less than 4 min and the minimum detectable serum concentration was 50 ng/mL. In five patients undergoing chronic peritoneal dialysis, the mean serum concentrations +/- SD at 1, 6, and 48 h after the intraperitoneal administration of a single dose of fluconazole were, respectively, 325 +/- 75, 928 +/- 159, and 607 +/- 80 ng/mL.

Overview of medically important antifungal azole derivatives

Fungal infections are a major burden to the health and welfare of modern humans. They range from simply cosmetic, non-life-threatening skin infections to severe, systemic infections that may lead to significant debilitation or death. The selection of chemotherapeutic agents useful for the treatment of fungal infections is small. In this overview, a major chemical group with antifungal activity, the azole derivatives, is examined. Included are historical and state of the art information on the in vitro activity, experimental in vivo activity, mode of action, pharmacokinetics, clinical studies, and uses and adverse reactions of imidazoles currently marketed (clotrimazole, miconazole, econazole, ketoconazole, bifonazole, butoconazole, croconazole, fenticonazole, isoconazole, oxiconazole, sulconazole, and tioconazole) and under development (aliconazole and omoconazole), as well as triazoles currently marketed (terconazole) and under development (fluconazole, itraconazole, vibunazole, alteconazole, and ICI 195,739).

Activities of fluconazole (UK 49,858) and ketoconazole against ketoconazole-susceptible and -resistant Candida albicans

We have compared the activities of fluconazole and ketoconazole against ketoconazole-susceptible and -resistant strains of Candida albicans in a neutropenic-site rabbit model. Oral treatment with fluconazole resulted in much higher serum and extravascular concentrations of this antifungal agent than did comparable doses of ketoconazole. Fluconazole had no additional in vivo activity against the ketoconazole-susceptible strains; no fungicidal activity was observed with peak drug levels as high as approximately 75 micrograms/ml in the infection sites. Significant fungistatic activity against the ketoconazole-resistant strains was observed with fluconazole treatment (80 mg/kg), but not with less fluconazole (20 mg/kg) or with ketoconazole (approximately 67 mg/kg). In vitro susceptibility tests separated the ketoconazole-susceptible strains from the ketoconazole-resistant strains, but the results were variable when the resistant strains were tested with fluconazole.

Azole antifungal agents: emphasis on new triazoles

Many advances have been made in antifungal therapy over the last three decades. Itraconazole and fluconazole, two investigational triazole agents, are the most recent additions to the list of antifungal drugs. This review has focused primarily on their mechanisms of action, favorable pharmacologic properties, and spectra of activity against a broad range of systemic pathogens. Itraconazole and fluconazole show much promise as orally active agents, with less potential for toxicity than the currently available azoles. Fluconazole and, to a lesser degree, itraconazole are especially promising therapies for cryptococcal meningitis. In addition, fluconazole may prove to be highly effective in urinary tract infections caused by Candida species and other fungi. Ongoing and future clinical trials will more clearly define the specific roles of itraconazole and fluconazole in the treatment of systemic mycoses.

Comparison of fluconazole and amphotericin B in treating histoplasmosis in immunosuppressed mice

Fluconazole (UK-49,858) was compared with amphotericin B in treating histoplasmosis in female AKR mice immunosuppressed with either cyclophosphamide or cortisone. Both drugs protected animals from a lethal challenge with Histoplasma capsulatum, but neither regimen resulted in cures since viable organisms were cultured from spleens of survivors.

Comparison of relative susceptibilities of Candida species to three antifungal agents as determined by unstandardized methods

Three groups of isolates, each comprising four isolates of Candida species, were selected for their diversity of susceptibilities to amphotericin B, flucytosine, or ketoconazole. The isolates were distributed in duplicate and in blinded fashion to three laboratories where a total of eight procedures were performed for each drug. From the decoded results, intralaboratory variability among replicate determinations was found usually to fall within a fourfold range. Interlaboratory variation, however, was 16-fold or greater for all isolates, ranging to 50,000-fold differences for some isolates. Relative susceptibilities of isolates within each method could be determined in 11 of the 24 drug-method combinations and agreed with the reference rank order in all but one instance. Our findings underscore the lack of agreement among laboratories for the susceptibility testing of yeasts but indicate that such differences could likely be resolved by standardization without loss of clinical value.