Direct observation of nystatin binding to the plasma membrane of living cells.

Nystatin is an antifungal polyene macrolide which is widely applied to treat yeast infections. Nystatin has also been used as a laboratory tool to inhibit endocytic processes in mammalian cells. The interaction of nystatin with model membranes has been studied thoroughly by various spectroscopic methods, making use of its weak fluorescence in the ultraviolet (UV). Studying its interaction with cells would require direct imaging, which, so far, required attachment of a fluorophore to nystatin. Using UV-sensitive microscopy, we show here how to visualize the interaction of nystatin with the plasma membrane (PM) directly. We find that nystatin forms micron-sized aggregates in buffer, and molecular dynamics simulations confirm that nystatin rapidly self-assembles into aggregates in aqueous solution. Using UV-sensitive microscopy, we find that large nystatin aggregates adhere to the surface of Chinese Hamster Ovarian (CHO) cells, causing slow spreading of nystatin fluorescence into the PM. Binding of nystatin to CHO cells does not interfere with cellular uptake or lateral membrane diffusion of the cholesterol analogue TopFluor-cholesterol (TF-Chol). Nystatin binds extensively to the PM of yeast cells as inferred from a strong UV signal in this membrane. Loading a yeast mutant unable to synthesize ergosterol with cholesterol gave much less nystatin membrane staining compared to loading such cells with ergosterol. These results explain the selective fungicidal effect of nystatin by differential interaction of nystatin with yeast membranes containing ergosterol compared to the mammalian cholesterol. Our combined experimental and computational approach provides a toolset for future design of new polyene macrolides.

Formulation, characterization and in vitro evaluation of antifungal activity of Nystatin micro emulsion for topical application.

The current research aims at development and assessment of o/w nystatin microemulsion. The pseudoternary phase diagrams were developed to determine microemulsion existence regions by water titration method. Nystatin was liquefied in the blend of oil phase, surfactant and cosurfactant. Microemulsion was made by deliberate mixing of water and stirring in this blend. The S-mix (surfactant-cosurfactant mixtures) of the ratio 1:2 was found better than 1:1 and 2:1 S-mix ratios. In vitro permeation studies by Franz diffusion cell revealed faster rate of nystatin release from such microemulsion (5.37µg/cm2/h) as compared to nystrin (4.79µg/cm2/h), a commercially available aqueous suspension. Kinetic modeling demonstrated zero order drug release and release mechanism found to be anomalous i.e. superposition of dispersion and swelling controlled drug release. Antifungal activity was performed using well diffusion method in vitro against Candida albicans cultures grown on Sabouraud's dextrose agar. The results also confirmed the high diffusion rate of drug from microemulsion as compared to aqueous suspension. The outcomes of this study propose that topical microemulsion of nystatin provides better antifungal activity as compared to emulsion gels or aqueous suspensions.

Effectiveness and Pharmacokinetic evaluation of Geonistin® (Oxytetracyline and Nystatin) Vaginal Tablets for Unspecific and Mixed Vulvovaginal Infections (GENIE Study).

The GENIE study was performed to evaluate the effectiveness and systemic exposure to oxytetracycline in local treatment of unspecific and mixed vulvovaginal infections characterized by vaginal discharge with Geonistin® vaginal tablets (100 mg oxytetracycline and 100 000 IU nystatin). The total number of subjects enrolled was 189. The treatment had beneficial effects in 100% of the study population. According to the Nugent score, the treatment had a positive effect in 89.2% of participants. The microbiological cure rate was 78.8%. Oxytetracycline concentration levels were from 13.3 to 32.2 ng/mL in 11 out of 15 subjects, and in four subjects the levels were below 10 ng/mL. Geonistin® had a beneficial effect on the unspecific and mixed vulvovaginal infections characterized by vaginal discharge in all efficacy and safety outcomes. Microbiological and the Nugent score efficacy measures confirmed clinical effectiveness. Beneficial efficacy results were achieved with only a few non-serious adverse events.

Novel microparticulate systems for the vaginal delivery of nystatin: development and characterization.

To develop more effective antifungal microparticulate therapeutic systems for the treatment of Candida vaginitis, microparticles containing nystatin were elaborated by emulsification/internal gelation method. Three types of microparticles were successfully prepared, alginate microparticles, chitosan and poloxamer 407 coated alginate microparticles. DSC and FT-IR studies were performed to test the efficacy of the method. After physicochemical characterization, mean particle sizes ranged from 36.088 µm to 56.146 µm. The encapsulation efficiency was found to be similar for alginate and chitosan coated microparticles and lower for poloxamer 407 coated. Optimal mucoadhesive properties in all kind of microparticles where exhibited. Release studies showed the best kinetic parameters for poloxamer 407 coated microparticles. After ex vivo permeation studies through porcine vaginal mucosa, and determination of the amount of nystatin retained as well as microbiologic studies performed, it could be inferred that the developed microparticulate systems offered an antifungal effect against Candida albicans without toxic systemic absorption.

Pharmacokinetics, tissue distribution and immunomodulatory effect of intralipid formulation of nystatin in mice.

OBJECTIVES: We developed a novel lipid formulation of nystatin suitable for parenteral administration, nystatin-intralipid (NYT-IL), with antifungal activity and reduced toxicity in mice. We investigated the pharmacokinetics, tissue distribution and immunomodulatory effect of NYT-IL in mice. METHODS: Nystatin levels in serum and organs were determined using HPLC after NYT-IL or nystatin administration in mice. The levels of the pro-inflammatory cytokines tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) and the anti-inflammatory cytokine interleukin 10 (IL-10) produced by splenocytes from mice injected with NYT-IL or nystatin were evaluated by an ELISA assay. RESULTS: Injection of NYT-IL resulted in similar levels and similar kinetics of nystatin in serum, higher concentrations in the liver and lower concentrations in the kidneys, in comparison with nystatin injection. Injection of mice with NYT-IL yielded higher levels of IL-10 than that of nystatin, whereas the levels of TNF-α and IFN-γ induced by NYT-IL were lower than those elicited by nystatin. CONCLUSIONS: Since polyene treatment is associated with nephrotoxicity, lower levels of nystatin in the kidneys following NYT-IL injection suggest the possibility of reduced toxicity. As the acute infusion-related adverse effects associated with polyene treatment are considered to be induced by pro-inflammatory cytokines, a higher level of anti-inflammatory and lower levels of pro-inflammatory cytokines elicited by NYT-IL administration suggest the possibility of amelioration of such effects. In summary, the altered pharmacokinetics, tissue distribution and immune response due to the use of this intralipid formulation of nystatin merit further research towards the development of a therapeutic agent against invasive mycoses.

Cholesterol sequestration by nystatin enhances the uptake and activity of endostatin in endothelium via regulating distinct endocytic pathways.

Specific internalization of endostatin into endothelial cells has been proved to be important for its biologic functions. However, the mechanism of endostatin internalization still remains elusive. In this study, we report for the first time that both caveolae/lipid rafts and clathrin-coated pits are involved in endostatin internalization. Inhibition of either the caveolae pathway or the clathrin pathway with the use of chemical inhibitors, small interfering RNAs, or dominant-negative mutants alters endostatin internalization in vitro. Intriguingly, cholesterol sequestration by nystatin, a polyene antifungal drug, significantly enhances endostatin uptake by endothelial cells through switching endostatin internalization predominantly to the clathrin-mediated pathway. Nystatin-enhanced internalization of endostatin also increases its inhibitory effects on endothelial cell tube formation and migration. More importantly, combined treatment with nystatin and endostatin selectively enhances endostatin uptake and biodistribution in tumor blood vessels and tumor tissues but not in normal tissues of tumor-bearing mice, ultimately resulting in elevated antiangiogenic and antitumor efficacies of endostatin in vivo. Taken together, our data show a novel mechanism of endostatin internalization and support the potential application of enhancing the uptake and therapeutic efficacy of endostatin via regulating distinct endocytic pathways with cholesterol-sequestering agents.

Enhancement of dissolution of nystatin from buccoadhesive tablets containing various surfactants and a solid dispersion formulation.

Nystatin is commonly employed to treat fungal infections in the mouth. It is not absorbed via the stomach and it will therefore not treat fungal infections in any part of the body other than the mouth. Nystatin buccoadhesive tablets release the drug very slowly due to the poor solubility of nystatin in water and also the presence of polymers with mucoadhesive properties. Therefore, the aim of the present study was to improve drug release from buccoadhesive tablets, while retaining adequate mucoadhesive properties. To this end, a solid dispersion of nystatin: lactose (1:3) was prepared and mixed with xanthan. The effects of hydrophilic surfactants such as cremophor RH40 and Tween 80 on drug release and mucoadhesive properties of nystatin tablets were also investigated as were swelling and erosion indices and strength of bioadhesion in vitro to a biological membrane. The interaction between nystatin and lactose in solid dispersion formulation was investigated by XRPD, FT-IR and DSC. The results showed that a solid dispersion formulation and mucoadhesive tablets containing surfactants led to faster drug release than their simple physical mixtures. Drug release was also faster from a solid dispersion compared to tablets containing surfactants. Swelling and erosion results showed that tablets made of a solid dispersion swelled and eroded faster than a physical mixture formulation. The presence of surfactant slightly increased the degree of swelling and erosion of buccoadhesive tablets.

Oral sustained release nystatin tablets for the treatment of oral candidiasis: formulation development and validation of UV spectrophotometric analytical methodology for content determination.

OBJECTIVE: In this study, oral sustained release mucoadhesive nystatin tablets were developed to increase nystatin contact time with the oral cavity and mask its unpleasant taste. METHODS: The best formulation studied included sustained release agents and it was submitted to physical-mechanical characterization, taste assessment and clinical test in twelve patients. The ultraviolet-visible nystatin methodology was also developed and validated in parallel as an alternative to the pharmacopoeial microbiological dosage method. RESULTS: The best formulation developed in this study included sustained release agents. The efficacy of this formulation was verified through a clinical assessment, showing that this formulation is more effective (100%) than the commercial oral nystatin suspension used traditionally (50%). Moreover, the UV absorption spectrophotometry method developed to validate the methodology for nystatin content analysis for new oral tablets was shown to be specific, linear, exact and reproducible, as recommended by the ICH regulations. CONCLUSION: The oral nystatin tablets developed showed to present faster therapeutic response than the oral aqueous solution through the preliminary clinical assays. The UV absorption spectrophotometry method showed to be an attractive test for the usual routine in the pharmaceutical industry.

Novel mucoadhesive extended release tablets for treatment of oral candidosis: "in vivo" evaluation of the biopharmaceutical performance.

Mucoadhesive tablets containing nystatin (10 mg) were evaluated in vivo. The assays were carried out with 12 healthy volunteers and the concentration of nystatin in saliva was determined at different times. Tablets remained attached to the buccal mucosa during 270 min +/- 30 min. No evidence of ulceration or bleeding was observed. Typical appearance of intact human buccal mucosa was seen before and after contact with the tablet. The tablets were well accepted by the volunteers, although most of the volunteers reported a light bitter taste, probably due to nystatin. Concentration of nystatin in saliva was several times higher than MIC over a period of approximately 4.5 h, which was in agreement with the behavior observed in vitro. These results allow us to infer that the administration of these mucoadhesive tablets could be advantageous compared to conventional formulations and mucoadhesive extended-release tablets might produce better therapeutic performance than conventional formulations in the treatment of oral candidosis.

Quantitative determination of nystatin in human plasma using LC-MS after inhalative administration in healthy subjects.

The antifungal polyene antibiotics nystatin was tested in a clinical trial to describe pharmacokinetics and safety after repeated administration of Nystatin "Lederle" sterile powder in healthy volunteers. To monitor the nystatin concentration-time profile in plasma we developed a sensitive method in the range of 1-100ng/ml based on liquid chromatography coupled with tandem mass spectrometry. The target substance was separated from the biological matrix on C(18) solid-phase extraction cartridges with methanol. The Chromatography was performed isocratically using a reversed phase Caltrex Resorcinearene column. The mobile phase consisted of 5mM ammonium formate buffer and acetonitrile (40:60, v/v). The mass spectrometer works with electrospray ionization in its positive selected ion monitoring (SIM) mode using the respective MH(+) ions, m/z 926.6 for nystatin and m/z 924.4 for amphotericin B as internal standard. The method validation was performed according to the demands and international criteria for validation of bioanalytical methods and was successfully applied to the quantification of nystatin in human plasma in the pharmacokinetic trial.

Safety, efficacy and pharmacokinetics of tuftsin-loaded nystatin liposomes in murine model.

Present study was performed to evaluate the efficacy, toxicity and pharmacokinetics of antifungal drug nystatin incorporated in immunomodulator tuftsin-bearing liposomes. In vitro toxicity of free nystatin and nystatin incorporated in tuftsin-free or tuftsin-loaded liposomes was assessed by incubation of nystatin formulations with human erythrocytes. The toxicity profile of free nystatin and liposomal formulations of nystatin with or without tuftsin was also analyzed by monitoring the level of blood urea nitrogen (BUN) and serum creatinine in the treated BALB/c mice. The results of the present work showed that tuftsin-loaded nystatin liposomes like conventional nystatin liposomes exerted less toxicity to human erythrocytes as compared with free nystatin. Moreover, mice treated with tuftsin-loaded nystatin liposomes showed insignificant elevation in the biochemical values of serum creatinine and blood urea. The stability of nystatin liposomes upon incorporation of tuftsin was evaluated by monitoring the leakage of the entrapped drug in human serum. Tuftsin-loaded liposomes held nystatin for longer duration in the presence of serum than identical nystatin liposomes without tuftsin. Pharmacokinetics of the both tuftsin-free or tuftsin-loaded liposomal formulations nystatin was analyzed by determining the level of nystatin in the systemic circulation of mice at different time points. Mice injected with tuftsin-loaded nystatin liposomes showed higher level of the drug in the systemic circulation compared with those treated with conventional nystatin liposomes. The efficacy of tuftsin-loaded nystatin liposomes against A. fumigatus was evaluated by assessing the fungal burden in the lungs of treated mice. Treatment with tuftsin-loaded nystatin liposomes was most effective in eliminating fungal burden from lung tissues of infected mice compared to those treated with free nystatin or nystatin liposomes without tuftsin. The immunopotentiating activity, increased stability and less toxicity of tuftsin-incorporated nystatin liposomes, supports the idea for its prophylactic and therapeutic use in the clinical setting.

Liposomal polyene antibiotics.

Polyene antibiotics (i.e., amphotericin B and nystatin) have been incorporated into lipid-based delivery systems to decrease their toxicity and enhance their therapeutic index, the most common being liposomes. This chapter describes the protocols for preparing liposomal amphotericin B and determining the efficacy and toxicity of the formulations in animals. Furthermore, methods for determining the pharmacokinetics and drug distribution after administration of amphotericin B in lipid-based delivery systems are discussed. Procedures for comparing the toxicity of different amphotericin B formulations in cell culture studies are also elucidated.

[Intestinal candidiasis: modern therapeutic tactics].

Bowels candidiasis is an urgent problem not only for gastroenterology but also for other fields of medicine--gynecology, dentistry, phthisiology, surgery, etc. as this disease is directly related with the manifestations of systemic candidiasis in other organs. The diagnostics algorithm includes the detection of a filamentary form (pseudomyceliums) of micromycetes of the Candida genus in the morphological study of a tissue sampling of the bowels mucous coat. The drug of choice for the treatment of bowels candidiasis is Pimafucin (Natamycin) having a local action on the Candida fungi in the intestinal lumen in the absence of any systemic absorption of the drug or any side effects.

Chitosan delivery systems for the treatment of oral mucositis: in vitro and in vivo studies.

Oral mucositis is a frequent and potentially severe complication of radiation or chemotherapy for cancer. Associated with atrophy and ulceration of the oral mucosa is an increased risk of infection, and the most common pathogenic agent is Candida. Chitosan is an excellent candidate for the treatment of oral mucositis. Its bioadhesive and antimicrobial properties offer the palliative effects of an occlusive dressing and the potential for delivering drugs, including anti-candidal agents. The aim of this study was to develop an occlusive bioadhesive system for prophylaxis and/or treatment of oral mucositis. Gel and film formulations were prepared using chitosans at different molecular weights and in different solvents. Nystatin, which is considered as a prophylactic agent for oral mucositis was incorporated into the formulations. The in vitro release of nystatin from the formulations was decreased with the increasing molecular weight of chitosan. The effect of the formulations was investigated in vivo in hamsters with chemotherapy-induced mucositis. Mucositis scores in groups treated with nystatin incorporated into gel and suspension formulations were significantly lower (p < 0.05) than those treated with the chitosan gel alone. Survival of animals in the treated groups was higher than that in the control group. The retention time and distribution of the gels in the oral cavity were investigated in healthy volunteers. A faster distribution of nystatin in the oral cavity was obtained using the suspension compared to the gels, but the nystatin saliva level decreased rapidly as well. A drug concentration above the minimum inhibitory concentration (MIC) value for Candida albicans (0.14 microg/ml) was maintained for longer periods of time at the application site (90 min) than at the contralateral site (45 min) in the oral cavity.

Drug release from carbomer:carbomer sodium salt matrices with potential use as mucoadhesive drug delivery system.

In vitro mucoadhesion, water uptake, and drug release of nystatin (N) from matrices of carbomer (C) and lyophilized carbomer sodium salt (CNaL) mixtures were evaluated. Matrices with different ratios C:CNaL were prepared by direct compression. Commercial C as well as lyophilized powder (CL) were used. In vitro mucoadhesion increased as the proportion of C in the matrix was raised. The same effect was observed when C was replaced by CL. Matrices in which C was replaced by CL showed an increase of both water uptake and release rates. Besides, the release of N from matrices CL:CNaL exhibited a kinetics with Super Case II (n>1) mechanism. However, for C:CNaL matrices, drug release was slower and exhibited a biphasic profile with a first stage characterized by either an anomalous (n<1, for C>or=50%) or a Case II (n approximately 1.0, C<50%) mechanisms. After that period, the mechanism changed to Super Case II transport (n>1).

Comparative drug disposition, urinary pharmacokinetics, and renal effects of multilamellar liposomal nystatin and amphotericin B deoxycholate in rabbits.

The comparative drug dispositions, urinary pharmacokinetics, and effects on renal function of multilamellar liposomal nystatin (LNYS; Nyotran) and amphotericin B deoxycholate (DAMB; Fungizone) were studied in rabbits. Drug concentrations were determined by high-performance liquid chromatography as total concentrations of LNYS and DAMB. In comparison to a standard dose of 1 mg of DAMB/kg of body weight, therapeutic dosages of LNYS, i.e., 2, 4, and 6 mg/kg, resulted in escalating maximum concentrations (Cmax) (17 to 56 microg/ml for LNYS versus 3.36 microg/ml for DAMB; P<0.001) and values for the area under the concentration-time curve from 0 to 24 h (AUC(0-24)) (17 to 77 microg.h/ml for LNYS versus 12 microg.h/ml for DAMB; P<0.001) in plasma but a significantly faster total clearance from plasma (0.117 to 0.080 liter/h/kg for LNYS versus 0.055 liter/h/kg for DAMB; P=0.013) and a < or =8-fold-smaller volume of distribution at steady state (P=0.002). Urinary drug concentration data revealed a > or =10-fold-higher Cmax (16 to 10 microg/ml for LNYS versus 0.96 microg/ml for DAMB; P=0.015) and a 4- to 7-fold-greater AUC(0-24) (63 to 35 microg.h/ml for LNYS versus 8.9 microg.h/ml for DAMB; P=0.015) following the administration of LNYS, with a dose-dependent decrease in the dose-normalized AUC(0-24) in urine (P=0.001) and a trend toward a dose-dependent decrease in renal clearance. Except for the kidneys, the mean concentrations of LNYS in liver, spleen, and lung 24 h after dosing were severalfold lower than those after administration of DAMB (P, <0.002 to <0.001). Less than 1% each of the total dose of LNYS was recovered from the kidneys, liver, spleen, and lungs; in contrast, a quarter of the total dose was recovered from the livers of DAMB-treated animals. LNYS had dose-dependent effects on glomerular filtration and distal, but not proximal, renal tubular function which did not exceed those of DAMB at the highest investigated dosage of 6 mg/kg. The results of this experimental study demonstrate fundamental differences in the dispositions of LNYS and DAMB. Based on its enhanced urinary exposure, LNYS may offer a therapeutic advantage in systemic fungal infections involving the upper and lower urinary tracts that require therapy with antifungal polyenes.

[Acute generalized exanthematous pustulosis induced by drugs with low-digestive absorption: acarbose and nystatin]. / Pustulose exanthématique aiguë généralisée induite par des médicaments à faible absorption intestinale: l'acarbose et la nystatine.

INTRODUCTION: Acarbose and nystatin are usually well-tolerated drugs because of their minimal intestinal absorption. We report herein two cases of acute generalized exanthematous pustulosis induced by these two molecules. CASES REPORT: A 43 year-old man with a history of insulin-deficient diabetes was admitted to our department for a febrile generalized cutaneous pustular erythema, that had appeared 48 hours after acarbose (Glucor) introduction. Acarbose was discontinued and the eruption resolved in one week. A 29 year-old man developed a flexural erythema twenty four hours after nystatin (Mycostatin) treatment, progressing towards a febrile pustular erythroderma, with elevated neutrophilic and eosinophilic counts. The lesions regressed rapidly with topical steroid treatment. The patch tests performed a few months later with Mycostatin and nystatin were positive. DISCUSSION: The clinical presentation of these two patients was typical of acute generalized exanthematous pustulosis, according to the EuroSCAR group criteria and acarbose and nystatin were the most likely factors that caused the disease according to the French unexpected or toxic drug reaction assessment. The minimal intestinal absorption of these two molecules explains their usual good tolerance. However, some cases of toxiderma have already been reported. There is the first described case of acute generalized exanthematous pustulosis with acarbose. Our two observations underline the possibility of severe toxiderma induced by low-absorbed and low-blood concentration molecules and focus on the need to take them in account in the toxiderma anamnesis.

Pharmaceutical design of the liposomal antimicrobial agents for infectious disease.

From the point of view of pharmaceutical design, development of carrier system of antimicrobial agents with functional properties should be required. We introduced here the development-process of liposomal formulations of polyene macrolide antibiotics, amphotericin B (AmB) and nystatin as injectable dosage forms. Both development of the effective encapsulation method of these drugs in liposomes and investigation of the encapsulation mechanism and the molecular states of them are important to determine the optimum lipid composition for therapeutic uses. Enhanced encapsulation of these hydrophobic drugs, long-circulation in blood and high targetability are the required functional properties for the carrier system. Low encapsulation of AmB in liposomes has been overcome by the incorporation of polyethylene glycol-lipid derivatives, DSPE-PEG. Both the hydration with 9% sucrose solution and the complex formation between AmB and DSPE-PEG contribute not only to the enhanced encapsulation of AmB in liposomes but also to the stability and long-circulation properties in blood. Encapsulation mechanism and the molecular states of AmB in liposomes were also investigated by several methods. AmB-encapsulating PEG liposomes (PEG-L-AmB) with optimum lipid composition also showed reduced toxicity and higher therapeutic efficacy on murine model of pulmonary aspergillosis than that of conventionally used AmB formulations. Further enhanced therapeutic effects was observed by using AmB-encapsulating PEG immunoliposomes (34A-PEG-L-AmB) carrying monoclonal antibodies at the distal ends of the PEG chains. On the contrary to AmB, encapsulation characteristics of nystatin were apparently different from that of AmB, though the chemical structure is very similar. Self-association of nystatin with sterol-free lipid membrane dominantly influences on the encapsulation characteristics. Many experiments about the encapsulation of antimicrobial agents in liposomes have been demonstrated by many researchers, but there are not so much drugs developed for commercially used. Optimization of the formulation of functional drug-carrier system should be important for the practical uses.

The reproductive and developmental toxicity of the antifungal drug Nyotran (liposomal nystatin) in rats and rabbits.

Nyotran is a liposomally encapsulated i.v. formulation of the antifungal polyene nystatin. This drug was evaluated in a series of reproductive toxicity studies, according to the guidelines outlined by the International Conference on Harmonization (ICH). A fertility and early embryonic development study (SEG I) and a prenatal and postnatal development (SEG III) study were conducted in rats, and embryo-fetal development (SEG II) studies were conducted in rats and rabbits. Nyotran was administered iv in all studies. In SEG I and SEG III, rats were administered daily doses of 0.5, 1.5, or 3.0 mg/kg Nyotran. In both studies, parental mortality and toxicity in the 3.0 mg/kg dose group necessitated the lowering of the high dose to 2.0 mg/kg/day. Parental toxicity, in the form of decreased body weights, decreased food consumption, and piloerection were also observed at the 1.5 mg/kg/day dose level in the SEG I and SEG III studies. Despite the parentally toxic doses in the SEG I study, there was no effect of Nyotran on F0 male or female fertility or early embryonic development of F1 offspring. In the SEG III study, lactational body weights of the F1 generation were decreased at all Nyotran dose levels. There was no effect on pre-wean developmental landmarks, but post-wean development was affected by Nyotran administration at all dosage levels. Preputional separation was delayed in the 1.5 and 3.0/2.0 mg/kg/day F1 offspring, auditory startle function was decreased in F1 females at all dose levels, and motor activity was decreased in male F1 offspring at all dose levels. However, there were no treatment-related effects on the subsequent mating of the F1 generation and resulting F2 offspring. In SEG II studies, rats and rabbits were also administered 0.5, 1.5, or 3.0 mg/kg/day of Nyotran during gestation. The high dose in these SEG II studies was not lowered, as the maternal animals were able to tolerate the shorter duration of dosing. Maternal effects in rabbits were observed only in the high-dose group and were limited to decreased food consumption and decreased absolute and relative liver weight. Decreased food consumption in high-dose dams and clinical weight loss in some animals at the mid- and high-dose levels evidenced maternal toxicity in rats. Nyotran did not have any effect on Caesarian section parameters in either rats or rabbits and no effect on the incidence of fetal malformations in rabbits. A statistically significant increase in mild hydrocephaly, observed in 4 rat fetuses, was seen at the highest dose level of 3.0 mg/kg/day. The biological significance and relationship to Nyotran treatment of this finding is not clear. This finding may represent a change in the background incidence or a change in the pattern of responsiveness of this strain of rat fetus to the test chemical. Toxicokinetic data were also collected in the SEG II rabbit and rat studies for comparison to human exposures. In both species, systemic exposure to the nystatin at effective antifungal concentrations was demonstrated. The systemic exposures in rats and rabbits were, however, considerably less than have been reported in humans administered clinical doses of 2 or 4 mg/kg/day Nyotran. Thus, humans tolerate higher dosages and systemic exposures of Nyotran relative to rats and rabbits and there is no margin of safety in either dosage level or systemic exposure to drug. Given this lack of a margin of safety and the effects on postnatal development in F1 rats, caution should be exercised when using this drug in females of childbearing potential.

Compartmental pharmacokinetics and tissue distribution of multilamellar liposomal nystatin in rabbits.

The plasma pharmacokinetics of multilamellar liposomal nystatin were studied in normal, catheterized rabbits after single and multiple daily intravenous administration of dosages of 2, 4, and 6 mg/kg of body weight, and drug levels in tissues were assessed after multiple dosing. Concentrations of liposomal nystatin were measured as those of nystatin by a validated high-performance liquid chromatography method, and plasma concentration data were fitted into a two-compartment open model. Across the investigated dosage range, liposomal nystatin demonstrated nonlinear kinetics with more than proportional increases in the AUC(0-24) and decreasing clearance, consistent with dose-dependent tissue distribution and/or a dose-dependent elimination process. After single-dose administration, the mean C(max) increased from 13.07 microg/ml at 2 mg/kg to 41.91 microg/ml at 6 mg/kg (P < 0.001); the AUC(0-24) changed from 11.65 to 67.44 microg. h/ml (P < 0.001), the V(d) changed from 0.205 to 0. 184 liters/kg (not significant), the CL(t) from 0.173 to 0.101 liters/kg. h (P < 0.05), and terminal half-life from 0.96 to 1.51 h (P < 0.05). There were no significant changes in pharmacokinetic parameters after multiple dosing over 14 days. Assessment of tissue concentrations of nystatin near peak plasma levels after multiple dosing over 15 days revealed preferential distribution to the lungs, liver, and spleen at that time point. Substantial levels were also found in the urine, raising the possibility that renal excretion may play a significant role in drug elimination. Liposomal nystatin administered to rabbits was well tolerated and displayed nonlinear pharmacokinetics, potentially therapeutic peak plasma concentrations, and substantial penetration into tissues. Pharmacokinetic parameters were very similar to those observed in patients, thus validating results derived from infection models in the rabbit and allowing inferences to be made about the treatment of invasive fungal infections in humans.