Toxicity of amphotericin B plus flucytosine in 194 patients with cryptococcal meningitis

Meningitis caused by Cryptococcus neoformans var. gattii and var. neoformans in Papua New Guinea

Eleven cases of cryptococcal meningitis were diagnosed and biotyped from September 1991 to August 1992 in Papua New Guinea (PNG). Seven isolates were Cryptococcus neoformans var. gattii from paediatric and adult patients, one with diabetes mellitus and 4 were C. neoformans var. neoformans from adults, of whom 2 had human immunodeficiency virus type 1 (HIV-1) infection, and one each had tuberculosis and Plasmodium vivax malaria. Significant clinical findings were headache, fever, meningism, vomiting, photophobia, papilloedema and cranial nerve lesions. Five patients (45.5%) died; 3 of these were adults with var. gattii and 2 were men with both var. neoformans and HIV-1 infections. This prospective tropical study documents the emergence of C. neoformans var. neoformans in patients with HIV-1 infection in a country where previously var. gattii had predominated in the immunocompetent. There has been no earlier report of cryptococcosis in an HIV-1 seropositive patient in PNG. Despite presumed exposure to both varieties of C. neoformans, var. gattii infections had been most frequent. As HIV-1 spreads, the proportion of hosts infected with var. neoformans may rise. The course of meningitis caused by the 2 varieties of C. neoformans may differ, with mortality in the tropics remaining particularly high. In PNG the environmental source of C. neoformans remains elusive.

Itraconazole and flucytosine+itraconazole combination in the treatment of experimental cryptococcosis in hamsters

The efficacy of two different daily doses of itraconazole (ITRA) and the combination of flucytosine (5-FC) with ITRA in the treatment of an experimental model of cryptococcosis in hamsters was studied. Five groups of 20 animals each were inoculated by the intracardiac route with 10(5) cells of Cryptococcus neoformans. Treatment started 3 days after the infection, and was administered by gavage for 30 days. ITRA was applied at a daily dose of 25 mg kg-1 or 50 mg kg-1 and the combination of 5-FC and ITRA was given at 75 mg kg-1 day-1 or 50 mg kg-1 day-1 respectively. One group of 20 hamsters received the vehicle and was used as a control group. Treatment evaluation was based on the following parameters: number of surviving animals 60 days after the infection; presence of encapsulated yeasts on microscopic examination of wet preparations of brain, lungs, liver, spleen and kidneys at necropsy; and brain qualitative (massive seeding) and quantitative cultures (determination of colony forming units, CFU). ITRA 50 (50 mg kg day-1) was the most effective treatment according to the studied parameters; 70% of brain cultures became negative and 95% of the treated hamsters survived to the end of the study period. ITRA efficacy was dose dependent. The combination of ITRA with 5-FC was less effective than administering the drugs separately; the reason for this finding is not known. The results obtained in this study should encourage the use of high doses of ITRA in cases of disseminated cryptococcosis in humans.

Comparison of D0870 and fluconazole in the treatment of murine cryptococcal meningitis

Cryptococcal meningitis is a common infection in patients with AIDS. Using a murine cryptococcosis model, we compared treatment with a new triazole, D0870, and fluconazole. Groups of ICR (Institute for Cancer Research) mice were infected intracerebrally with eight different isolates of Cryptococcus neoformans variety neoformans with different in vitro susceptibilities to fluconazole. For survival studies mice were challenged with two to four times LD(50) or six to nine times LD(50). Treatment was given for 10 days. Mice were observed through to day 30. To assess the effect of treatment on fungal tissue burden, mice received a three to five times LD(50) inoculum and treatment for 10 days. They were sacrificed on day 12 and serial dilutions of brain homogenates were cultured. Fluconazole prolonged survival primarily in isolates which were susceptible in vitro. D0870 prolonged survival in all isolates except one, which was also resistant in vitro to D0870 and fluconazole. Both drugs reduced colony counts of all isolates. D0870 warrants further development for use in cryptococcosis, and appears effective for isolates relatively resistant to fluconazole. There is a relative correlation of in vivo and in vitro susceptibility to D0870 as well as fluconazole.

Cryptococcosis in the era of AIDS--100 years after the discovery of Cryptococcus neoformans

Although Cryptococcus neoformans and cryptococcosis have existed for several millennia, a century has passed since the discovery of this encapsulated yeast and its devastating disease. With the advent of the AIDS pandemic, cryptococcal meningitis has emerged as a leading cause of infectious morbidity and mortality and a frequently life-threatening opportunistic mycosis among patients with AIDS. Both basic and clinical research have accelerated in the 1990s, and this review attempts to highlight some of these advances. The discussion covers recent findings, current concepts, controversies, and unresolved issues related to the ecology and genetics of C. neoformans; the surface structure of the yeast; and the mechanisms of host defense. Regarding cell-mediated immunity, CD4+ T cells are crucial for successful resistance, but CD8+ T cells may also participate significantly in the cytokine-mediated activation of anticryptococcal effector cells. In addition to cell-mediated immunity, monoclonal antibodies to the major capsular polysaccharide, the glucuronoxylomannan, offer some protection in murine models of cryptococcosis. Clinical concepts are presented that relate to the distinctive features of cryptococcosis in patients with AIDS and the diagnosis, treatment, and prevention of cryptococcosis in AIDS patients.

Comparison of high-performance liquid chromatography and bioassay for the determination of 5-fluorocytosine in serum

An HPLC method using a reverse phase system, an isocratic mobile phase and simple protein precipitation and a plate diffusion bioassay using an amphotericin B resistant strain of Candida pseudotropicalis for the measurement of 5-fluorocytosine in serum were compared. Both methods permit a determination of 5-fluorocytosine in sera also in the presence of amphothericin B. The correlation between bioassay and HPLC runs was found to be r = 0.96. Both methods are useful for monitoring the serum level of 5-fluorocytosine in clinical routine.

Influence of diet on experimental toxicity of amphotericin B deoxycholate

The effects of pre- and postprandial levels of lipids in serum on the experimental in vivo and in vitro toxicities of amphotericin B deoxycholate (AmB-d) were studied. Normal OF1 mice were tested at baseline, after normal feeding, after 3 h of fasting, or after a sequence of feeding and fasting and vice versa. The 50% lethal dose (LD50) of AmB-d was significantly higher in fed mice than in mice which fasted or at baseline (2.38 +/- 0.12 versus 1.53 +/- 0.2 and 1.50 +/- 0.1 mg/kg of body weight, respectively; P < 0.05). When different nutritional regimens were alternated over a short period, the level of in vivo AmB-d toxicity was dictated by the last feeding regimen. Serum triglycerides, but not cholesterol in very-low-density and low-density lipoproteins, correlated significantly (P < 0.01) with the LD50 of AmB. In vitro experiments showed that the addition of human serum reduced AmB-d-induced toxicity against human erythrocytes, but serum drawn after fasting was less protective than postprandial serum. However, neither serum decreased the in vitro activity of AmB-d against Candida albicans. Circular dichroism, a method that enables the amount of free AmB to be measured, showed that both mouse and human total serum lipoproteins bound more AmB-d when serum was isolated postprandially than when it was obtained after fasting. Our results show that AmB-d toxicity is reduced by feeding-induced modifications in serum lipids. The influence of food intake on the clinical toxicity of the drug merits being investigated.

In vitro renal toxicity and in vivo therapeutic efficacy in experimental murine cryptococcosis of amphotericin B (Fungizone) associated with Intralipid

We compared the experimental toxicities and activities of deoxycholate amphotericin B (d-AmB) dissolved in glucose (Dd-AmB) or mixed with 20% Intralipid (ILd-AmB). In vitro, ILd-AmB against renal tubular cells in primary culture. In vivo, the toxicities and activities of Dd-AmB and ILd-AmB were studied in DBA2 mice with cryptococcosis. The maximum tolerated dose of intravenously administered d-AmB, i.e., the dose that induced less than 15% mortality because of toxicity, was 1.7 to 2.5 times higher when it was administered as ILd-AmB than when it was administered as Dd-AmB. Both treatments given intravenously at the same dose were equivalent for improving the survival of mice and reducing CFU counts in infected tissue, but at maximum tolerated doses, ILd-AmB (2 mg/kg of body weight) was more effective than Dd-AmB (0.8 to 1.2 mg/kg). AmB concentrations in spleen, liver, lung, and kidney were measured by high-pressure liquid chromatography 4 and 24 h after a single injection of 1.2 mg of Dd-AmB per kg, 1.2 mg of ILd-AmB per kg, or 2 mg of ILd-AmB per kg. In a given organ, AmB levels were similar after administration of 1.2 mg of Dd-AmB or ILd-AmB per kg but were significantly higher after administration of 2 mg of ILd-AmB per kg. The lower level of toxicity of ILd-AmB might be explained by circular dichroism experiments, showing that ILd-AmB contained 10-fold less soluble oligomeric AmB, which is believed to be the toxic form of the drug, than Dd-AmB. We conclude that ILd-AmB is as efficient as Dd-AmB and is better tolerated than Dd-AmB in mice with experimental cryptococcosis. By allowing higher doses of AmB to be infused, Intralipid enhances AmB concentrations in infected sites, and thus the therapeutic activity of the drug.

Use of antifungal therapy in hospitalized patients. I. Results prior to the marketing of fluconazole

OBJECTIVE

To evaluate the use of antifungal agents in hospitalized patients prior to marketing of fluconazole and to assess characteristics associated with their use.

DESIGN

A cohort of hospitalized patients receiving topical or systemic antifungal therapy was monitored concurrently.

SETTING

Sixty-nine hospitals ranging in size from 100 to more than 500 beds, 70.1 percent affiliated with medical schools.

PATIENTS

Participating clinical pharmacists each identified 15 consecutive patients receiving systemic antifungal therapy and 5 consecutive patients receiving topical antifungal therapy at their institutions. Data collection began October 1989 and ended March 1990.

INTERVENTION

All data collected were observational in nature, and no patient intervention was required.

MEASURES

Characteristics of patients receiving antifungal therapy were compared using t-tests and chi-square tests. Utilization and patterns of use of antifungal therapy were reported.

RESULTS

The most common risk factors necessitating antifungal therapy, in descending order, were: administration of broad-spectrum antibiotics and/or presence of invasive catheters, carcinoma, AIDS, leukemia or lymphoma, diabetes mellitus, solid organ or bone marrow transplantation, and chronic obstructive pulmonary disease. Five hundred seventeen patients received systemic therapy and 464 (89.7 percent) received a single systemic agent. Of these, 242 (52.2 percent) received amphotericin B, 215 (46.3 percent) received ketoconazole, 6 (1.3 percent) received flucytosine, and 1 (0.2 percent) received intravenous miconazole. Fifty-three patients received two systemic agents either concurrently or consecutively. Ketoconazole was most often used for presumed or documented oral, urogenital, or esophageal infections and amphotericin B was the preferred agent for disseminated infections and fungemia (p < 0.001). Almost half of the patients receiving amphotericin B or ketoconazole (48.3 percent) received these drugs as empiric therapy. Documented infections were more likely to be treated with amphotericin B (54.8 percent) than with ketoconazole (27.4 percent) (p < 0.001). The predominant fungal isolates were Candida albicans, Candida spp., and unspecified yeasts. Amphotericin B toxicity led to discontinuation of drug therapy in only 5.1 percent of cases. Two hundred sixty-nine patients (34.2 percent) received topical antifungal therapy only. Nystatin oral suspension was prescribed to 65.3 percent of the patients, clotrimazole troches to 23.0 percent, amphotericin B irrigation to 10.9 percent, and nystatin tablets to 0.8 percent.

CONCLUSIONS

The utilization patterns of antifungal agents in this survey follow established therapeutic guidelines. Prior to the introduction of fluconazole, amphotericin B was the agent of choice for documented systemic fungal infections. Ketoconazole was more often used for prophylaxis of fungal infections and treatment of oral and esophageal infections.

Fungicidal properties of defensin NP-1 and activity against Cryptococcus neoformans in vitro

Defensin NP-1, derived from the neutrophils of rabbits, was tested for its fungistatic and fungicidal activity against strains of Cryptococcus neoformans. The MICs for the encapsulated strains tested ranged from 3.75 to 15.0 micrograms of NP-1 per ml. The minimum fungicidal concentrations for these strains were similar to the MICs. An acapsular strain, however, had a lower MIC of 0.93 and minimum fungicidal concentration of 1.88 micrograms/ml. NP-1 demonstrated time-dependent and concentration-dependent killing of C. neoformans. Killing occurred rapidly in the first 20 min of exposure to NP-1 and was maximum at 90 to 120 min. Killing of C. neoformans by NP-1 was concentration dependent with 31% +/- 9% survival at 25 micrograms/ml, 13% +/- 4% survival at 50 micrograms/ml, 9% +/- 5% survival at 75 micrograms/ml, and 5% +/- 3% survival at 100 micrograms/ml. NP-1's fungicidal effect on C. neoformans was also inoculum dependent, with increased activity observed at 10(4) versus 10(5) or 10(6) cells per ml. In addition, stationary-phase C. neoformans was less susceptible to NP-1 killing than yeast cells in the logarithmic phase. Subinhibitory concentrations of both NP-1 (0.25 x MIC) and fluconazole (0.25 x MIC) acted synergistically in inhibiting growth of C. neoformans. Similar combinations of NP-1 and amphotericin B, however, did not yield synergy.

Cryptococcal meningitis: the place of itraconazole

Itraconazole, an orally active broad-spectrum triazole antimycotic, has demonstrated anti-Cryptococcus activity in vitro and in animal models of cryptococcal meningitis. The drug has been used by a number of clinical groups for the treatment of cryptococcal meningitis, predominantly in AIDS patients. A problem that has been found with ketoconazole is the relatively low absorption of the drug in AIDS patients. This has resulted in ketoconazole plasma levels below the MIC90 (1-5 micrograms ml-1) needed to eliminate Cryptococcus neoformans. In addition, tissue levels of ketoconazole are lower than plasma levels. For itraconazole, the required MIC90 for Cr. neoformans is 0.1 microgram ml-1, and the plasma levels in AIDS patients receiving 200-400 mg daily, even in the case of reduced absorption, are well above this MIC90. The itraconazole levels in the brain and in the meninges are higher than the plasma levels. Consequently, itraconazole has been considered a valid candidate for studies in patients with cryptococcal meningitis. Various treatment modalities have been used: primary oral therapy alone or in combination with amphotericin B or 5-fluorocytosine (5-FC); maintenance oral therapy after initial treatment with amphotericin B (with or without 5-FC); and first-line intravenous treatment in severely ill patients. The results were evaluated in four different groups. When the drug was given as primary oral therapy without combination with amphotericin B or 5-FC, the results depended greatly on the dose administered and on the life expectancy of the patient at inclusion. In general, daily doses of 400 mg were better than 200-mg doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative studies on the postantifungal effect produced by the synergistic interaction of flucytosine and amphotericin B on Candida albicans

A turbidometric method was used to measure Candida albicans yeast cell growth and to quantitate the postantifungal effect (PAFE) after exposure to various concentrations of flucytosine and amphotericin B, alone and in combination, for 2 hr at 30 degrees C. The drug concentrations used in the PAFE assays were determined by initial MIC and FIC (fractional inhibitory concentration) evaluations. The PAFE was calculated by the difference in time (hr) required for growth of the control and test cultures to reach the 0.5 absorbance level following removal of the drug by dilution. A synergistic PAFE was evidenced with combinations of the two drugs at concentrations below their individual MICs. Combinations of flucytosine (0.012 to 0.049 micrograms ml-1) and amphotericin B (0.195 to 0.39 micrograms ml-1) produced PAFEs ranging from 6.3 to 21.8 hr. These PAFEs persisted from 0.3 to 14.7 hr longer than those achieved when each of the two agents was assayed separately.

Acute and chronic effects of flucytosine on amphotericin B nephrotoxicity in rats

The combination of intravenous flucytosine (FC) in 0.9% saline (NaCl) and amphotericin B (AmB) provides synergistic antifungal activity and is associated with a lower incidence of nephrotoxicity than with AmB treatment alone. This study was conducted to examine whether flucytosine can influence renal function and whether it can modify the acute and chronic renal responses to AmB in the rat. In the in situ perfused rat kidney, FC at a concentration of 10 mg/kg/min for 15 min had a vasodilator effect, increasing renal blood flow by 2.5 +/- 0.7 ml/min, an effect not observed with vehicle. After the infusion of FC was stopped for 15 min, AmB induced a decrease in renal blood flow similar to that with both FC and vehicle. In a second series of studies, AmB (5 mg/kg/day intraperitoneally) was administered to four groups of rats for 7 days. In addition, the following groups received the intravenous daily interventions indicated: group 1, 5% dextrose in water (15 ml/kg/12 h); group 2, FC (150 mg/kg/12 h) in 0.9% saline (15 ml/kg/12 h); group 3, 0.9% saline (15 ml/kg/12 h); and group 4, FC (150 mg/kg/12 h) in 5% dextrose in water. Group 1 sustained a 77% decrease in creatinine clearance over the 7 days and a threefold increase in serum creatinine concentration (P of < 0.05). Groups 2, 3, and 4 sustained significantly less nephrotoxicity, with no change in serum creatinine concentration and only 38, 41, and 53% decreases in creatinine clearance, respectively (P of < 0.05), compared with that for group 1. AmB levels in renal tissue varied inversely to creatinine clearance (r of 0.57, P of < or = 0.005). However, no significant differences were found in levels in tissue between groups (P of 0.06). The results of this study suggest that FC has a small but significant effect in reducing chronic AmB-induced nephrotoxicity. This amelioration of renal injury is independent of saline administration. There was evidence that the extent of renal uptake of AmB related to the efficiency of renal function at the end of the experiment.

Activity of MS-8209, a nonester amphotericin B derivative, in treatment of experimental systemic mycoses

The in vitro and in vivo toxicities and activities of MS-8209, a new hydrosoluble amphotericin B (deoxycholate-amphotericin B [D-AmB]; Fungizone) derivative, were studied. In vitro, MS-8209 was less toxic than AmB against renal tubular cells in primary culture and less active against Candida albicans and Cryptococcus neoformans. However, at 10-fold the AmB concentration, MS-8209 in vitro antifungal activity paralleled that of AmB. Fifty-percent lethal doses of MS-8209 and D-AmB in OF1 noninfected mice were 26 and 2.3 mg/kg, respectively. Therapeutic efficacy of MS-8209 was assessed in murine candidiasis, cryptococcosis, and aspergillosis. In each model of infection, we determined the maximum tolerated dosages of MS-8209 and D-AmB, i.e., the dosage inducing less than 15% mortality due to toxicity; the efficacies of MS-8209 and D-AmB at their respective maximum tolerated dosages were compared. In candidiasis, MS-8209 (15 mg/kg) significantly increased the survival time compared with D-AmB (0.5 mg/kg). Both compounds were equally effective at reducing CFU counts in the kidney. MS-8209 was the most effective agent for increasing the survival time in cryptococcal meningoencephalitis and for reducing CFU counts in spleen, brain, and lung during both cryptococcal pneumonia and meningoencephalitis. In aspergillosis, MS-8209 and D-AmB similarly prolonged the survival of treated mice compared with controls. These results show that when MS-8209 and D-AmB were used at the maximum tolerated dosage, MS-8209 was as effective as or more effective than D-AmB for the treatment of systemic mycoses. These findings warrant further experiments to study the pharmacokinetic properties and toxicity of MS-8209 under conditions of chronic administration.

Comparison of nephrotoxicities of different polyoxyethyleneglycol formulations of amphotericin B in rats

The aim of the present study was to assess whether amphotericin B (AmB)-Myrj 59, AmB-polyoxyethyleneglycol 24 cholesterol (PC), and AmB-Synperonic A50 (SA50) were less nephrotoxic than AmB-deoxycholate (DC). Rats were treated with the different AmB formulations (10 mg/kg of body weight) intraperitoneally or with the surfactants alone. A group of control rats receiving the vehicle was also examined. After 6 days of daily intraperitoneal injections of AmB-DC, decreased body weight and glomerular filtration rate as well as increased degree of diuresis, uremia, microalbuminuria, and N-acetyl-beta-D-glucosaminidase excretion in urine were noted. Urinary excretion of potassium and sodium was also decreased in AmB-DC-treated rats. Most of these effects were more pronounced with AmB-PC and AmB-SA50. In contrast, AmB-Myrj 59 was less nephrotoxic than AmB-DC. Indeed, after 6 days of treatment with AmB-Myrj 59, the natriuria, kaliuria, albuminuria, and glomerular filtration rates were unchanged compared with those of controls. Moreover, the body weight loss and uremia increase of the rats treated by AmB-Myrj 59 were less than those of the rats treated with the commercial preparation. Among the surfactants, only PC was toxic for the rats. The intrinsic toxicity of PC and the higher systemic exposure to AmB could contribute to increased toxicities of AmB-PC and AmB-SA50, respectively. AmB-Myrj 59 was less nephrotoxic than AmB-DC at equivalent areas under the plasma concentration-time curves. These preliminary results suggest that this formulation could be a good alternative to the commercial product.

Influence of phospholipid/amphotericin B ratio and phospholipid type on in vitro renal cell toxicities and fungicidal activities of lipid-associated amphotericin B formulations

We studied the influence of the lipid/amphotericin B (AMB) ratio and the phospholipid type on the in vitro renal cell toxicity and antifungal efficacy of lipid-associated AMB (L-AMB). L-AMB was prepared at one of two different lipid/AMB ratios (1 and 40) by incubating AMB with empty small unilamellar vesicles, made from one of three different phospholipids: dipalmitoyl-, dimirystoyl-, and distearoylphosphatidylcholine (DPPC, DMPC, and DSPC, respectively). Renal cell toxicity, investigated through an assessment of the Na-dependent uptake of phosphate by proximal tubular cells, and fungicidal effect against Candida albicans were studied after 1 h of treatment at 37 degrees C. The amount of unbound AMB present in each L-AMB formulation was studied by use of circular dichroism. At a lipid/AMB ratio of 40, the three lipidic formulations were not toxic for renal cells but were less effective against C. albicans than AMB; however, DSPC-AMB, which contained 50% unbound AMB, was more effective against C. albicans than DPCC-AMB or DMPC-AMB, containing 0 and 13% unbound AMB, respectively. At a lipid/AMB ratio of 1, the antifungal effects of L-AMB and AMB were similar, whatever the phospholipid used, but only DMPC-AMB remained highly protective against AMB renal cell toxicity, despite the presence of the same amount of unbound AMB (50%) in DMPC-AMB and DPPC-AMB. We conclude that the in vitro activities and renal cell toxicities of different L-AMB formulations are influenced by the phospholipid type and the lipid/AMB ratio. The optimal ratio depends on the phospholipid itself. At a lipid/AMB ratio of 40, the antifungal activity depends mainly on the amount of unbound AMB in the formulation. At a lipid/AMB ratio of 1, the renal cell toxicity also depends on the fluidity of the phospholipid.

Synergistic postantifungal effect of flucytosine and fluconazole on Candida albicans

The in vitro efficacy of flucytosine and fluconazole, separately and in combination, with respect to induction of a postantifungal effect (PAFE) on Candida albicans was studied. PAFE refers to the persistent suppression of fungal cell growth following a short period of exposure to an antifungal agent. A turbidometric method was used to measure cell growth and to quantitate the PAFE following exposure of C. albicans yeast cells to different concentrations of the two agents for 2 h. The PAFE was determined by the difference in time (h) required for growth of the control and test cultures to increase to the 0.5 absorbance level following removal of the drug by dilution. Minimum (MIC) and fractional inhibitory concentration determinations were made and the data used for selecting the concentrations used in the PAFE evaluations. A synergistic interaction of the two drugs at concentrations well below their individual MICs was evidenced. Flucytosine:fluconazole ratios of 1:16-1:32 at concentrations ranging from 0.024-0.098 micrograms ml-1 and from 0.78-1.56 micrograms ml-1, with flucytosine and fluconazole, respectively, induced PAFEs which persisted for 2.5 h longer than those achieved when each of the two agents was assayed separately.

Antifungal agents used for deep-seated mycotic infections

The increased use of immunosuppressive regimens in organ transplantation and in the treatment of malignant lesions and the epidemic of acquired immunodeficiency syndrome (AIDS) are major reasons for the greater prevalence of fungal infections seen in clinical practice during the past decade. The traditional cornerstone of antifungal treatment, amphotericin B, continues to play a major role in deep-seated mycotic infections. The indications for intravenously administered miconazole have become limited. Orally administered flucytosine remains useful in certain infections, particularly cryptococcal meningitis. The new orally administered antifungal agents ketoconazole and fluconazole have been approved for clinical use and have supplanted amphotericin B in certain situations. Investigational antifungal agents, including liposomal amphotericin B, itraconazole, and saperconazole, hold promise for the future. Active investigation in the development of new antifungal agents is expected to continue.

Comparison of SCH 39304 and its isomers, RR 42427 and SS 42426, for treatment of murine cryptococcal and coccidioidal meningitis

SCH 39304 (304) and its isomers, SCH 42426 (426) and SCH 42427 (427), are new orally administered antifungal azole derivatives. In this study, we compared the efficacy of 304 with that of 426 and 427 in murine models of cryptococcal and coccidioidal meningitis. On day 18 postinfection with Cryptococcus neoformans, controls showed 80% mortality. The 50% protective doses calculated at this day were 0.56 mg of 304 per kg of body weight, 23.5 mg of 426 per kg, and 0.11 mg of 427 per kg. Controls with coccidioidal meningitis all succumbed, and treated mice at the same time point showed 50% protective doses of 10.8 mg/kg for 304, 200 mg/kg for 426, and 2.1 mg/kg for 427. We conclude that isomer 427 is five times as potent, whereas 426 is 1/50th as potent as 304 in these experimental mycoses.

Treatment of murine cryptococcal meningitis with an SCH 39304-amphotericin B combination

Cryptococcal meningitis was induced in BALB/c mice by intracerebral infection with Cryptococcus neoformans. Drug therapy was initiated 1 day later, with mice receiving amphotericin B (AMB), SCH 39304, combination therapy, or no drug therapy (controls). Most, but not all, combinations showed additive benefits, significantly prolonging survival and reducing organism counts in tissues compared with those in controls and groups which received the drugs independently. Optimum protection was obtained when a single dose of 10 mg of AMB per kg of body weight was combined with a fairly narrow SCH 39304 dose range. AMB antagonism did not occur with any regimen tested. AMB-azole combinations may be reasonable alternatives for patients who fail standard cryptococcosis therapeutic regimens.

Effect of flucytosine on renal function in the rat

Flucytosine (5-fluorocytosine), a potent antimycotic drug against various systemic infections such as candidosis, aspergillosis and cryptococcosis, is extensively excreted by the kidneys, yet its possible role in renal function is not known. In the present study flucytosine, administered intravenously, increased significantly renal blood flow (RBF) by 26% from 5.06 +/- 0.9 ml/min/kidney. The renal vasodilation was combined with an elevation of creatinine clearance of 140% from a baseline value of 0.23 +/- 0.11 ml/min/kidney. This improvement in renal function was accompanied by an increase in filtration fraction, urine volume and potassium excretion. In comparison, rats administered an equal amount of 5% glucose only showed no changes in the values of these parameters.

In vitro comparative evaluations of the postantifungal effect: synergistic interaction between flucytosine and fluconazole against Candida albicans

In vitro comparative evaluations were performed to study the efficacy of combinations of flucytosine and fluconazole in producing a postantifungal effect (PAFE) on Candida albicans. Initial studies were done to determine MIC, FIC (fractional inhibitory concentration) and optimal PAFE parameters. A turbidometric method was used to measure yeast cell growth following exposure to different concentrations of the two drugs for periods of 0.5, 1 or 2 h at temperatures of 30 degrees C and 37 degrees C. The PAFE was determined by the difference in time (h) required for growth of the control and test cultures to reach the 0.5 absorbance level following removal of the drug by dilution. Ten strains of C. albicans were then assayed (30 degrees C; 2 h exposure time) and a synergistic PAFE was evidenced with the two drugs at concentrations well below their individual MICs. PAFEs ranging from 3.8 to 10.5 h, which persisted for 1.2-2.5 h longer than those achieved with either agent separately, were evidenced when flucytosine and fluconazole were combined (flucytosine: fluconazole ratios of 1:16-1:32) at concentrations ranging from 0.024 to 0.098 micrograms ml-1 and 0.78 to 1.56 micrograms ml-1 respectively. The concentrations of each agent required to produce an optimal PAFE varied according to the C. albicans strain being assayed.

Cost implications of alternative treatments for AIDS patients with cryptococcal meningitis. Comparison of fluconazole and amphotericin B-based therapies

The extra demands placed upon health care resources by management of AIDS patients have increased the focus on cost implications of therapeutic alternatives. Cryptococcal meningitis is a common life-threatening infection in AIDS patients, usually treated with amphotericin B, often in combination with flucytosine. Administered intravenously, this therapy is associated with frequent and often severe side effects. Fluconazole is a new alternative which can be given orally once daily and has fewer such side effects. The purpose of this study was to examine the cost implications of these different therapies for both primary and maintenance treatment of cryptococcal meningitis. Comparison of these two therapies in recent clinical trials has indicated that fluconazole is at least as effective as amphotericin B, and therefore cost-minimisation analysis is an appropriate method to study the economic consequences of the alternative treatments. Patient management and resource-use information for both treatments was obtained using a modified Delphi technique with a panel of European physicians experienced in the treatment of this disease, and three models were developed to reflect the variability of practice evident among the panel members. U.K. health care costs were used to value these resources. The results indicated that, despite the higher cost of the drug itself, the costs associated with fluconazole were likely to be markedly less than those for amphotericin B for primary treatment, and similar or slightly cheaper for maintenance treatment. Over 1 year of treatment, the saving from the use of fluconazole would be in the range of 4000-14,000 pounds.

Flucytosine conversion to fluorouracil in humans: does a correlation with gut flora status exist? A report of two cases using fluorine-19 magnetic resonance spectroscopy

A relationship between the gut flora level, particularly gram-negative enterobacilli, and the in vivo flucytosine conversion to fluorouracil has been observed in humans from the fluorine-19 magnetic resonance spectroscopy analysis of urine from two patients treated with the flucytosine- (6 to 9 g/day) amphotericin B (1 mg/kg/day) combination. Indeed the percentage of fluorouracil metabolites was extremely low (less than 0.6% of total fluorinated compounds excreted) when the number of enterobacillary colonies was low (less than 10(3] and higher (3.5 to 8.8%) when enterobacillary colonies were under reconstitution or in the normal range (10(5) to 10(8]. The intestinal microflora assessment may therefore be of high interest to predict the risk of an additive flucytosine-induced myelotoxicity suspected to be due to fluorouracil during flucytosine chronic therapy.

Combined therapy with fluconazole and flucytosine in murine cryptococcal meningitis

To assess the possible beneficial effects of combined therapy (fluconazole and flucytosine) in the treatment of cryptococcal meningitis in the immunocompromised host, we compared therapy with fluconazole and flucytosine, individually and combined, in the experimental murine model. BALB/c athymic (nu/nu) mice were infected intracerebrally with 150 to 300 CFU of Cryptococcus neoformans. In mortality studies, treatment was initiated 24 h postinfection and continued for 10 to 14 days with either fluconazole (1 to 15 mg/kg of body weight per day), flucytosine (60 to 120 mg/kg/8 h), both drugs, or 0.3% Noble agar (control). Combined therapy delayed mortality significantly when compared with controls and single-drug regimens. This was observed over a broad range of doses. Quantitative determinations of CFU in brain tissue demonstrated a significantly lower burden of C. neoformans in mice receiving combined therapy. The results indicate that combined therapy with fluconazole and flucytosine is superior to single-drug therapy.

Fungemia in a university hospital 1984-1988. Clinical and mycological characteristics

118 episodes of fungemia occurring at Rigshospitalet, Copenhagen, between 1984 and 1988 were reviewed retrospectively. Underlying diseases in the patients were dominated by malignancies, primarily hematological disorders, and intraabdominal diseases requiring major abdominal surgery. Predisposing factors identified in the patients were ongoing antibacterial chemotherapy (83%), central venous catheters (72%), major abdominal surgery (39%), and neutropenia (32%). 120 fungal strains were isolated, of which 88 (73%) were Candida albicans, 23 strains representing 8 other Candida species were also isolated, as were 9 strains belonging to 7 other fungal genera. There were only 5 strains resistant to 5-fluorocytosine (MICs greater than or equal to 25 mg/l), and no strain was resistant to amphotericin B. Treatment with antifungal agents was given in 78 patients, generally a combination of amphotericin B and 5-fluorocytosine. In 14 patients (all non-hematological) the only treatment was removal of a permanent central venous catheter. The outcome was poor in patients with hematological disorders (mortality 76%), whereas patients with malignant and non-malignant intraabdominal diseases had a mortality of 35%. All patients with a permanent central venous catheter as the only risk factor recovered rapidly after removal of the catheter.

Improvement of amphotericin B activity during experimental cryptococcosis by incorporation into specific immunoliposomes

Cryptococcosis is an opportunistic infection that is responsible for increased morbidity and mortality in patients with the acquired immunodeficiency syndrome. The high toxicity of the antifungal agent that is mainly used against cryptococcosis, amphotericin B (AMB), accounts for the need for new treatments, especially in patients with the acquired immunodeficiency syndrome because of the high relapse rate of cryptococcosis. Drug targeting may be one of these alternate treatments. Since we have demonstrated that an immunoglobulin G1 (IgG1) anti-Cryptococcus neoformans serotype A monoclonal antibody (E1) was protective during experimental cryptococcosis in mice, we investigated whether specific targeting of AMB with liposomes that bear E1 would improve the therapeutic index of the drug. For that purpose, in vitro and in vivo experiments were designed to compare the specificities and activities of these liposomes with those of control immunoliposomes bearing a nonrelated IgG1 monoclonal antibody (CY34). The immunoliposomes were prepared by covalently linking E1 or CY34 and small unilamellar vesicles. When immunoliposomes were incubated with yeast cells, only E1-bearing liposomes recognized C. neoformans. In vivo, mice that were treated 24 h after infection with one injection of AMB (0.12 mg/kg of body weight) intercalated into E1-bearing liposomes survived significantly longer than did those given the same dose of AMB alone or AMB intercalated into nontargeted liposomes or control immunoliposomes. None of the mice that were given control treatments did statistically better than those that were given AMB. Keeping in mind that this kind of therapy requires knowledge of the antigenic type of the infecting organism, the results suggest that specific targeting of small doses of AMB improve the efficacy of AMB and might be an alternative to the use of larger doses of AMB.

Sodium loading treatment for amphotericin B-induced nephrotoxicity

The increased frequency and duration of antifungal treatment with amphotericin B in immunocompromised patients has stimulated a great deal of research into the mechanisms of its nephrotoxic effects and treatment modalities designed to attenuate these effects. A review of amphotericin B-induced nephrotoxicity, the underlying pathophysiologic mechanisms, and the role of salt loading as a means of minimizing renal impairment are described. Both animal and human studies regarding the efficacy of sodium loading are presented as well as a case report describing the use of salt supplementation over a prolonged course of therapy.

Prevention of amphotericin-B-induced nephrotoxicity by loading with sodium chloride: a report of 1291 days of treatment with amphotericin B without renal failure

An open, prospective study was performed to evaluate the clinical usefulness of sodium chloride loading for prevention of amphotericin-B-induced nephrotoxicity in 37 patients requiring 44 courses of amphotericin B treatment. The median duration of the treatment course was 22 days (range, 9-136 days), and mean cumulative dose per patient was 1117 mg (range, 231-7831 mg). During amphotericin B treatment, all patients received 50 to 100 ml of 10% sodium chloride (85 to 171 mmol NaCl) via an intravenous line for prevention of amphotericin-B-induced nephrotoxicity evaluated by serum creatinine levels. Using this regimen, none of the patients developed significant nephrotoxicity (increase in serum creatinine of more than twice baseline level, or serum creatinine level greater than or equal to 2.0 mg/dl, respectively) despite the co-administration of other potentially nephrotoxic drugs. It was not necessary to discontinue treatment with amphotericin B in any of the patients. There were no side effects due to sodium chloride loading. Our results demonstrate that sodium chloride loading is useful for the prevention of amphotericin-B-induced nephrotoxicity.

Performance characteristics of two bioassays and high-performance liquid chromatography for determination of flucytosine in serum

We compared the accuracy and precision of two microbiological methods and one high-pressure liquid chromatography (HPLC) procedure used to measure the concentrations of flucytosine in serum. On the basis of an analysis of six standards, all methods were judged reliable within acceptable limits for clinical use. With the biological methods, a slight loss of linearity was observed in the 75- to 100-micrograms/ml range. Compared with the bioassays, the HPLC method did not present linearity problems and was more precise and accurate in the critical zone of 100 micrograms/ml. On average, results obtained with patient sera containing 50 to 100 micrograms of flucytosine per ml were 10.6% higher with the HPLC method than with the bioassays. Standards for the biological assays may be prepared in serum or water.

Effects of amphotericin B on the excretory function and the colloid clearance capacity of the perfused rat liver

The effects of amphotericin B (AmB) on the hepatic excretory function and the colloid clearance capacity were investigated in the perfused rat liver. AmB at 5 or 10 microM caused dose-dependent reductions in bile and perfusate flow rates and in biliary bile acid (BA) excretion. BA concentration in bile tended to increase, due to a prominent reduction in bile water induced by the drug. At 5 microM, AmB also caused an increase in [14C]sucrose clearance by the liver and a release of hepatocytic enzymes into the perfusate. These alterations were not related to the decrease in the perfusate flow induced by AmB. In addition, the drug, at 5 microM, caused a significant decrease in the colloidal carbon clearance by the liver. In this case also, the effect was independent of the reduction in the perfusate flow induced by the drug. The toxic effects of AmB on the rat liver could be interpreted as a derangement of the cell membrane functional integrity, which causes cholestasis, enzyme leakage and an impairment of the reticuloendothelial system function. This latter effect deserves careful evaluation of its clinical implications.

Candidiasis

Candida spp. are the most common fungal pathogens isolated in immunocompromised hosts, particularly cancer patients. Numerous clinical manifestations of candidiasis have been recognized, including localized infection such as oropharyngeal candidiasis or focal hepatic candidiasis, and disseminated infection resulting from hematogenous spread, with or without documented fungemia. Granulocytopenic patients are particularly at risk. Candida albicans is isolated in approximately 40% of cases of fungemia, other Candida spp. now also commonly being isolated. The rate of morbidity and mortality secondary to candidiasis is still significant despite numerous attempts to develop better diagnostic techniques, and more effective means of chemoprophylaxis and therapy. Currently, new antifungal agents and galenic preparations of amphotericin B are being evaluated with the aim of improving the prognosis of candidiasis in immunocompromised hosts.

Current concepts in cryptococcosis

Cryptococcus neoformans has become an increasingly important pathogen. Cryptococcosis is an important cause of morbidity and mortality in immunocompromised hosts and is the second most common fungal infection complicating AIDS. In recent years, research has focused on the host defenses against Cryptococcus and has led to an improved understanding of the capsular virulence of the organism, the mechanisms of T-cell defenses, and the role of phagocytic cells in the fungistasis and killing of cryptocci. Amphotericin B with or without flucytosine has clearly improved treatment of cryptococcosis, but therapy is associated with significant toxicity. Current investigation is focused on the triazoles, which may offer improved therapy for cryptococcosis. In this report, we review recent developments in the understanding of the host defenses against Cryptococcocus and discuss current recommendations for the management of cryptococcosis.

In vitro and in vivo evaluation of antifungal agents

The evaluation of any antifungal agent involves the determination of its in vitro and in vivo activity against pathogenic and/or opportunistic fungi. The in vitro evaluation is followed by an in vivo evaluation in animal models, and clinical trials in humans. From the first report of the efficacy of the iodides for the treatment of sporotrichosis (1903) until the introduction of the imidazoles (azoles, 1960s), the number of antifungal agents available was very limited, including griseofulvin (1939), nystatin (1950), amphotericin B (1956), and flucytosine (1964). This paper briefly reviews the status of the antifungal agents currently used, and gives a more in depth evaluation of progress during recent years in the search for new antifungal drugs. Efforts to improve the efficacy of the current antifungal agents are also reviewed.

Treatment of systemic fungal infections: recent progress and current problems

Systemic mycoses continue to emerge as life-threatening infections. Considerable progress in treating these infections is being achieved through better application of established available antifungal agents (amphotericin B, flucytosine, miconazole and ketoconazole), and through development of promising investigational agents (fluconazole, itraconazole). Systemic fungal infections, however, continue to present major problems, including clinical resistance, microbiological resistance, emergence of new pathogens, and involvement of more immunocompromised patients. The purpose of this paper, therefore, is to review the recent progress and current problems in treatment of systemic fungal infections.