Comparative safety, tolerance, and pharmacokinetics of amphotericin B lipid complex and amphotericin B desoxycholate in healthy male volunteers

Role of Amphotericin B in the Treatment of Mucormycosis

BACKGROUND

Regardless of the most recent inclusion of mold-active agents (isavuconazole and posaconazole) to antifungal agents against mucormycosis, in conjunction with amphotericin B (AMB) items, numerous uncertainties still exist regarding the treatment of this rare infection. The order Mucorales contains a variety of fungi that cause the serious but uncommon fungal illness known as mucormycosis. The moulds are prevalent in nature and typically do not pose significant risks to people. Immunocompromised people are affected by it.

OBJECTIVE

This article's primary goal is to highlight the integral role that AMB plays in this condition.

METHODS

Like sinusitis (including pansinusitis, rhino-orbital, or rhino-cerebral sinusitis) is one of the many signs and symptoms of mucormycosis. The National Center for Biotechnology Information (NCBI) produces a variety of online information resources for review articles on the topic-based mucormycosis, AMB, diagnosis of mucormycosis and the PubMed® database of citations and abstracts published in life science journals. These resources can be accessed through the NCBI home page at https://www.ncbi.nlm.nih.gov.

RESULTS

The article provides a summary of the pharmacological attributes of the various AMB compositions accessible for systemic use.

CONCLUSION

The article demonstrates the traits of the drug associated with its chemical, pharmacokinetics, stability, and other features, and illustrates their most useful characteristics for clinical application.

- Amphotericin B: A drug of choice for Visceral Leishmaniasis

Visceral leishmaniasis or Kala-azar is a vector-borne disease caused by an intracellular parasite of the genus leishmania. In India, Amphotericin B (AmB) is a first-line medication for treating leishmaniasis. After a large-scale resistance to pentavalent antimony therapy developed in Bihar state, it was rediscovered as an effective treatment for Leishmania donovani infection. AmB which binds to the ergosterol of protozoan cells causes a change in membrane integrity resulting in ions leakage, and ultimately leading to cell death. The treatment effect of liposomal AmB can be seen more quickly than deoxycholate AmB because, it has some toxic effects, but liposomal AmB is significantly less toxic. Evidence from studies suggested that ABLC (Abelcet) and ABCD (Amphotec) are as effective as L-AmB but Liposomal form (Ambisome) is a more widely accepted treatment option than conventional ones. Nevertheless, the world needs some way more efficient antileishmanial drugs that are less toxic and less expensive for people living with parasitic infections caused by Leishmania. So, academics, researchers, and sponsors need to focus on finding such drugs. This review provides a summary of the chemical, pharmacokinetic, drug-target interactions, stability, dose efficacy, and many other characteristics of the AmB and their various formulations. We have also highlighted the clinically significant aspects of PKDL and VL co-infection with HIV/TB.

Sensitive LC-MS/MS Methods for Amphotericin B Analysis in Cerebrospinal Fluid, Plasma, Plasma Ultrafiltrate, and Urine: Application to Clinical Pharmacokinetics

Neurocryptococcosis, a meningoencephalitis caused by Cryptococcus spp, is treated with amphotericin B (AmB) combined with fluconazole. The integrity of the brain-blood barrier and the composition of the cerebrospinal fluid (CSF) may change due to infectious and/or inflammatory diseases such as neurocryptococcosis allowing for the penetration of AmB into the central nervous system. The present study aimed to develop LC-MS/MS methods capable of quantifying AmB in CSF at any given time of the treatment in addition to plasma, plasma ultrafiltrate, with sensitivity compatible with the low concentrations of AmB reported in the CSF. The methods were successfully validated in the four matrices (25 μl, 5-1,000 ng ml-1 for plasma or urine; 100 μl, 0.625-250 ng ml-1 for plasma ultrafiltrate; 100 μl, 0.1-250 ng ml-1 for CSF) using protein precipitation. The methods were applied to investigate the pharmacokinetics of AmB following infusions of 100 mg every 24 h for 16 days administered as a lipid complex throughout the treatment of a neurocryptococcosis male patient. The methods allowed for a detailed description of the pharmacokinetic parameters in the assessed patient in the beginning (4th day) and end of the treatment with AmB (16th day), with total clearances of 7.21 and 4.25 L h-1, hepatic clearances of 7.15 and 4.22 L h-1, volumes of distribution of 302.94 and 206.89 L, and unbound fractions in plasma ranging from 2.26 to 3.25%. AmB was quantified in two CSF samples collected throughout the treatment with concentrations of 12.26 and 18.45 ng ml-1 on the 8th and 15th days of the treatment, respectively. The total concentration of AmB in plasma was 31 and 20 times higher than in CSF. The unbound concentration in plasma accounted for 77 and 44% of the respective concentrations in CSF. In conclusion, the present study described the most complete and sensitive method for AmB analysis in plasma, plasma ultrafiltrate, urine, and CSF applied to a clinical pharmacokinetic study following the administration of the drug as a lipid complex in one patient with neurocryptococcosis. The method can be applied to investigate the pharmacokinetics of AmB in CSF at any given time of the treatment.

Sixty years of Amphotericin B: An Overview of the Main Antifungal Agent Used to Treat Invasive Fungal Infections

Introduced in the late 1950s, polyenes represent the oldest family of antifungal drugs. The discovery of amphotericin B and its therapeutic uses is considered one of the most important scientific milestones of the twentieth century . Despite its toxic potential, it remains useful in the treatment of invasive fungal diseases owing to its broad spectrum of activity, low resistance rate, and excellent clinical and pharmacological action. The well-reported and defined toxicity of the conventional drug has meant that much attention has been paid to the development of new products that could minimize this effect. As a result, lipid-based formulations of amphotericin B have emerged and, even keeping the active principle in common, present distinct characteristics that may influence therapeutic results. This study presents an overview of the pharmacological properties of the different formulations for systemic use of amphotericin B available for the treatment of invasive fungal infections, highlighting the characteristics related to their chemical, pharmacokinetic structures, drug–target interactions, stability, and others, and points out the most relevant aspects for clinical practice.

Defining breakthrough invasive fungal infection-Position paper of the mycoses study group education and research consortium and the European Confederation of Medical Mycology

Breakthrough invasive fungal infections (IFIs) have emerged as a significant problem in patients receiving systemic antifungals; however, consensus criteria for defining breakthrough IFI are missing. This position paper establishes broadly applicable definitions of breakthrough IFI for clinical research. Representatives of the Mycoses Study Group Education and Research Consortium (MSG-ERC) and the European Confederation of Medical Mycology (ECMM) reviewed the relevant English literature for definitions applied and published through 2018. A draft proposal for definitions was developed and circulated to all members of the two organisations for comment and suggestions. The authors addressed comments received and circulated the updated document for approval. Breakthrough IFI was defined as any IFI occurring during exposure to an antifungal drug, including fungi outside the spectrum of activity of an antifungal. The time of breakthrough IFI was defined as the first attributable clinical sign or symptom, mycological finding or radiological feature. The period defining breakthrough IFI depends on pharmacokinetic properties and extends at least until one dosing interval after drug discontinuation. Persistent IFI describes IFI that is unchanged/stable since treatment initiation with ongoing need for antifungal therapy. It is distinct from refractory IFI, defined as progression of disease and therefore similar to non-response to treatment. Relapsed IFI occurs after treatment and is caused by the same pathogen at the same site, although dissemination can occur. These proposed definitions are intended to support the design of future clinical trials and epidemiological research in clinical mycology, with the ultimate goal of increasing the comparability of clinical trial results.

Comparative study on liposomal amphotericin B and other therapies in the treatment of mucosal leishmaniasis: A 15-year retrospective cohort study

Background

Liposomal amphotericin B (L-AMB) has been used for mucosal leishmaniasis (ML), but comparative studies on L-AMB and other drugs used for the treatment of ML have not been conducted. The present study aimed to evaluate the outcome of patients with ML who were treated with L-AMB.

Methods

This is a 15-year retrospective study of Brazilian patients with a confirmed diagnosis of ML. The therapeutic options for the treatment of ML consisted of L-AMB, amphotericin B lipid complex (ABLC), deoxycholate amphotericin B (d-AMB), itraconazole, antimonial pentavalent, or pentamidine. Healing, cure rate and adverse effects (AEs) associated with the drugs used to treat this condition were analyzed.

Results

In 71 patients, a total of 105 treatments were evaluated. The outcome of the treatment with each drug was compared, and results showed that L-AMB was superior to other therapeutic regimens (P = 0.001; odds ratio [OR] = 4.84; 95% confidence interval [CI] = 1.78–13.17). d-AMB had worse AEs than other treatment regimens (P = 0.001, OR = 0.09; 95% CI = 0.09–0.43). Approximately 66% of the patients presented with AEs during ML treatment. Although L-AMB was less nephrotoxic than d-AMB, it was associated with acute kidney injury compared with other drugs (P <0.05).

Conclusion

L-AMB was more effective than other therapies for the treatment of ML. However, a high incidence of toxicity was associated with its use. Therapeutic choices should be reassessed, and the development of new drugs is necessary for the treatment of ML.

Clinical Pharmacokinetics of Systemically Administered Antileishmanial Drugs

This review describes the pharmacokinetic properties of the systemically administered antileishmanial drugs pentavalent antimony, paromomycin, pentamidine, miltefosine and amphotericin B (AMB), including their absorption, distribution, metabolism and excretion and potential drug–drug interactions. This overview provides an understanding of their clinical pharmacokinetics, which could assist in rationalising and optimising treatment regimens, especially in combining multiple antileishmanial drugs in an attempt to increase efficacy and shorten treatment duration. Pentavalent antimony pharmacokinetics are characterised by rapid renal excretion of unchanged drug and a long terminal half-life, potentially due to intracellular conversion to trivalent antimony. Pentamidine is the only antileishmanial drug metabolised by cytochrome P450 enzymes. Paromomycin is excreted by the kidneys unchanged and is eliminated fastest of all antileishmanial drugs. Miltefosine pharmacokinetics are characterized by a long terminal half-life and extensive accumulation during treatment. AMB pharmacokinetics differ per drug formulation, with a fast renal and faecal excretion of AMB deoxylate but a much slower clearance of liposomal AMB resulting in an approximately ten-fold higher exposure. AMB and pentamidine pharmacokinetics have never been evaluated in leishmaniasis patients. Studies linking exposure to effect would be required to define target exposure levels in dose optimisation but have only been performed for miltefosine. Limited research has been conducted on exposure at the drug’s site of action, such as skin exposure in cutaneous leishmaniasis patients after systemic administration. Pharmacokinetic data on special patient populations such as HIV co-infected patients are mostly lacking. More research in these areas will help improve clinical outcomes by informed dosing and combination of drugs.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

Pharmacokinetics and pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

Pharmacokinetics of amphotericin B lipid complex in critically ill patients undergoing continuous venovenous haemodiafiltration

The objective of this study was to examine the effect of continuous venovenous haemodiafiltration (CVVHDF) on the pharmacokinetics of amphotericin B (AmB) in critically ill patients following administration of amphotericin B lipid complex (ABLC). Plasma and ultrafiltrate (UF) samples were collected from patients administered ABLC and either receiving or not receiving CVVHDF. Pharmacokinetic (PK) analysis was performed on eight profiles from patients receiving CVVHDF and six profiles from patients not receiving CVVHDF. For patients receiving CVVHDF, the following median PK data were calculated: area under the concentration-time curve (AUC) = 13.9 h·μg/mL, volume of distribution at steady state (V(ss)) = 1476L and drug clearance (CL) = 27.4 L/h; for patients not receiving CVVHDF, the corresponding median PK data were 11.5 h μg/mL, 2048 L and 43.7 L/h, respectively. The median half-lives calculated during the dosage interval (t(1/2int)) were 30.9 h and 32.5 h on and off CVVHDF, respectively, and the total range of t(1/2int) values was 15.6-180.4 h. Observed median peak concentrations on Day 1 were 0.563 μg/mL and 0.468 μg/mL in patients on and off CVVHDF, respectively. From AmB present in the UF, clearance via CVVHDF contributed<1% of total plasma clearance. The AmB concentration-time profiles for patients administered ABLC on and off CVVHDF were compared and no statistically significant differences in AUC, CL, t(1/2int) and V(ss) were observed. In conclusion, CVVHDF had no clinically significant effect on the pharmacokinetics of AmB following administration of ABLC.

Meeting the challenge of systemic fungal infections in cancer: nursing implications

Several factors have contributed to the increasing incidence of fungal infections over the last 2 decades, including the emergence of Acquired Immune Deficiency Syndrome, increased use of myelotoxic chemotherapy and organ transplantations, prolonged use of broad spectrum antibiotics and aggressive intensive care procedures. The two most common opportunistic fungal infections seen today are caused by Candida spp. and Aspergillus spp. Systemic fungal infections in immunocompromised patients have an extremely high mortality and require aggressive therapy. Skill in identifying early clinical features is therefore crucial and the multifaceted role of the nurse is of major importance in the management of at-risk patients. Nurses are the key resource in the prevention, early detection and treatment of fungal infection. All neutropenic patients should be thoroughly assessed at least twice a day, with special attention given to the most frequent sites of infection-the oral mucosa, lungs, skin, venepuncture sites and perineal area. Although fever is the hallmark of infection, it may be absent in the neutropenic patient who is unable to mount an adequate inflammatory response. It may also be masked by the use of certain drugs, such as steroids or analgesics. When systemic fungal infection is suspected, seriously ill patients require immediate antifungal therapy. Amphotericin B is currently the only agent with a sufficiently broad spectrum of activity to cover all the most common pathogens. Although conventional amphotericin B is effective, however, the required doses often carry significant toxicity, particularly nephrotoxicity. The new, lipid-based forms of amphotericin B, such as Abelcet, are indicated for and have been shown to be effective in patients with severe systemic and/or deep mycoses in whom conventional amphotericin B has proven ineffective or is contraindicated because of renal impairment, and in patients who have failed to respond to other antifungal agents.

Amphotericin B Formulations and Drug Targeting

Amphotericin B is a low-soluble polyene antibiotic which is able to self-aggregate. The aggregation state can modify its activity and pharmacokinetical characteristics. In spite of its high toxicity it is still widely employed for the treatment of systemic fungal infections and parasitic disease and different formulations are marketed. Some of these formulations, such as liposomal formulations, can be considered as classical examples of drug targeting. The pharmacokinetics, toxicity and activity are clearly dependent on the type of amphotericin B formulation. New drug delivery systems such as liposomes, nanospheres and microspheres can result in higher concentrations of AMB in the liver and spleen, but lower concentrations in kidney and lungs, so decreasing its toxicity. Moreover, the administration of these drug delivery systems can enhance the drug accessibility to organs and tissues (e.g., bone marrow) otherwise inaccessible to the free drug. During the last few years, new AMB formulations (AmBisome, Abelcet, and Amphotec) with an improved efficacy/toxicity ratio have been marketed. This review compares the different formulations of amphotericin B in terms of pharmacokinetics, toxicity and activity and discusses the possible drug targeting effect of some of these new formulations.

Amphotericin B–Associated Hyperbilirubinemia: Case Report and Review of the Literature

A 53-year-old woman with an intraabdominal infection secondary to Candida albicans experienced hyperbilirubinemia after receiving amphotericin B in two different formulations--amphotericin B deoxycholate and amphotericin B lipid complex. Only a few case reports of amphotericin B-induced hyperbilirubinemia have been documented in the literature, each with different patterns of corresponding abnormalities in liver function tests. The unpredictable nature of this adverse effect warrants monitoring of bilirubin levels and liver function at baseline and potentially during therapy with amphotericin B, regardless of formulation, dosage, or duration of therapy.

Apports des dérivés lipidiques de l’amphotéricine B dans la prise en charge des infections fongiques

Three lipid formulations of amphotericin B have been developed: amphotericin B colloidal dispersion, amphotericin B lipid complex, and liposomal amphotericin B. These three compounds differ by their lipid composition and therefore by their physical characteristics, their pharmacokinetics, and their safety and efficacy profile. There is a consensus to accept reduced toxicity of these formulations, especially reduced, but not absence of, renal toxicity as compared to amphotericin B deoxycholate. Few well-designed studies have been conducted and none of them demonstrated convincingly superiority in term of efficacy of any of the lipid preparations over amphotericin B deoxycholate. Recently a double blind randomized study compared a standard dose of 3 mg/kg/d of liposomal amphotericin B and a loading dose (10 mg/kg/d for 14 days and then the standard dose) in primary therapy of invasive filamentous fungal infections, mainly aspergillosis. Response rate at end of randomized therapy as well as survival at 12 weeks was numerically superior in the standard dose arm but this difference was not statistically significant. Lack of benefit of high dose liposomal amphotericin B in aspergillosis cannot yet be extrapolated to other filamentous fungal infections. Nephrotoxicity was substantially higher in the loading dose arm and this contraindicates its use in clinical practice.

Assessment of effective renal plasma flow, enzymuria, and cytokine release in healthy volunteers receiving a single dose of amphotericin B desoxycholate

The present study assessed potential subclinical markers of amphotericin B (AmB)-related nephrotoxicity and infusion-related reactions (IRR). Subjects were pretreated with diphenhydramine and acetaminophen and received a 500-ml bolus infusion of 0.9% sodium chloride prior to each effective renal plasma flow (ERPF) assessment. ERPF was measured before and after administration of a single 0.25-mg/kg intravenous AmB dose using technetium-99m mercaptoacetyltriglycine. Blood was collected before and 3 h after AmB infusion for tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) plasma concentrations. Overnight 12-h urine collections were performed before administration of AmB and for 2 nights after administration of AmB and analyzed for alpha and pi glutathione-S-transferases (GSTalpha and GSTpi, respectively) and N-acetyl-beta-d-glucosaminidase (NAG). Six men and six women with mean +/- standard deviation (SD) ages of 24.8 +/- 5.3 and 28.0 +/- 8.5 years, respectively, were studied. Baseline serum creatinine values were within the normal range and were unaltered after administration of AmB. The mean +/- SD decrease in ERPF after administration of AmB was significant (P < 0.05) in males (15.7 +/- 8.1%) but not females (9.5 +/- 14.0%). The GSTpi and GSTalpha indices increased significantly (P < 0.05) by two to fourfold and returned to baseline in males but were unaltered in females. NAG indices were unaffected by AmB. Six patients experienced an IRR that was associated with increased TNF-alpha (P < 0.05) but not IL-1beta (P = 0.09). These results suggest a potential sex-related difference in AmB-induced nephrotoxicity and provide a rationale for use of ERPF, urine GST, and TNF-alpha as subclinical markers of polyene-induced toxicity.

Treatment of Candida Infections with Amphotericin B Lipid Complex

The efficacy and renal safety of amphotericin B lipid complex (ABLC) were assessed in >900 patients with candidiasis. Overall, a favorable clinical response (cured or improved) was observed in 61% of patients infected with Candida species only, in 62% of patients infected with C. albicans, and in 61% of patients infected with a non-albicans Candida species. Clinical responses were similar in patients infected with invasive C. albicans and non-albicans Candida species (63% and 62%, respectively). Similarly, response rates of 60% and 59% were observed in patients infected with noninvasive C. albicans and non-albicans Candida species, respectively. Compared with patients who received lower doses of ABLC, patients who required higher doses of ABLC because of more-virulent infections did not demonstrate significant renal impairment, as assessed by end-of-therapy changes in serum creatinine level from baseline (median, 0.1 mg/dL; range, -3.9 to 2.4 mg/dL), incidence of serum creatinine doubling (16%), and need for new dialysis (7%). These data indicate the safety and efficacy of ABLC in treating candidiasis.

Use of amphotericin B lipid complex in elderly patients

OBJECTIVES

The safety and effectiveness of amphotericin B lipid complex (ABLC) treatment in elderly patients was investigated using a large multicenter database.

METHODS

Data analysis was conducted on retrospectively collected patient data from 572 patients >65 years of age and 2930 patients < or =65 years of age treated for fungal infections at 160 North American hospitals.

RESULTS

Patients were typically treated with ABLC for Candidiasis, multiple fungal pathogen infections and Aspergillosis, or were treated empirically. The median cumulative dose of ABLC in patients >65 years of age and those 65 years of age was similar (3000 and 3258 mg, respectively, P=0.127). Despite higher median pretreatment serum creatinine (S-Cr) among patients >65 years of age (1.7 mg/dl vs. 1.4 mg/dl, respectively), both groups showed only a 0.1mg/dl median S-Cr change from baseline by the end of therapy (P=0.525). Clinical response was 56 and 51%, respectively, in patients >65 years of age and patients 65 years of age or younger (P=0.049).

CONCLUSIONS

This study suggests that ABLC can be safely and effectively used in the treatment of invasive fungal disease in elderly patients.

Chronic disseminated candidiasis in patients with acute leukemia: emphasis on diagnostic definition and treatment

BACKGROUND

Chronic disseminated candidiasis (CDC) is a form of invasive fungal infection that occurs most commonly in patients with acute leukemia treated with chemotherapy. Recent studies have provided evidence for diagnostic alternatives to invasive procedures and more therapeutic options for the management of this complication. In order to put diagnostic criteria and methodological approach to the disease into the perspective of developing strategies for therapy, all relevant studies published in the English literature over the last 30 years were examined.

MATERIALS AND METHODS

The English-language articles located through MEDLINE (1966 to present) and from selected bibliographies.

RESULTS

There is increased recognition of CDC as complication of treatment with chemotherapy in patients with acute leukemia. Liver biopsy may not always be revealing or feasible to perform in some patients. Among the imaging modalities, magnetic resonance imaging has obtained preeminence as a non-invasive tool for the diagnosis of hepatosplenic fungal infections. Administration of amphotericin B (Amp B) in relatively large cumulative doses is needed to ensure appropriate control of the infection and prevention of future relapse. Patients intolerant of, or refractory to conventional Amp B have been successfully salvaged using fluconazole or lipid formulations of Amp B. A constellation of clinical, laboratory and radiologic parameters should be used to determine response and efficacy of therapy. There is sufficient evidence to support the safety and feasibility of continuing chemotherapy for acute leukemia in conjunction with antifungal treatment in patients diagnosed with CDC.

CONCLUSION

The development of CDC in patients with acute leukemia does not preclude further chemotherapy or constitute contraindication for bone marrow transplantation. Knowledge of the course and pattern of evolution of the disease and adopting aggressive therapeutic approach will likely reduce the morbidity and mortality from this complication.

Elongated supramolecular assemblies in drug delivery

This review presents different lipid-based elongated microstructures: tubules, cochleate cylinders and ribbons. Their composition, process of preparation and the mechanism behind their formation is discussed as well as their use as a drug delivery system.

Commonly used antibacterial and antifungal agents for hospitalised paediatric patients: implications for therapy with an emphasis on clinical pharmacokinetics

Due to normal growth and development, hospitalised paediatric patients with infection require unique consideration of immune function and drug disposition. Specifically, antibacterial and antifungal pharmacokinetics are influenced by volume of distribution, drug binding and elimination, which are a reflection of changing extracellular fluid volume, quantity and quality of plasma proteins, and renal and hepatic function. However, there is a paucity of data in paediatric patients addressing these issues and many empiric treatment practices are based on adult data. The penicillins and cephalosporins continue to be a mainstay of therapy because of their broad spectrum of activity, clinical efficacy and favourable tolerability profile. These antibacterials rapidly reach peak serum concentrations and readily diffuse into body tissues. Good penetration into the cerebrospinal fluid (CSF) has made the third-generation cephalosporins the agents of choice for the treatment of bacterial meningitis. These drugs are excreted primarily by the kidney. The carbapenems are broad-spectrum beta-lactam antibacterials which can potentially replace combination regimens. Vancomycin is a glycopeptide antibacterial with gram-positive activity useful for the treatment of resistant infections, or for those patients allergic to penicillins and cephalosporins. Volume of distribution is affected by age, gender, and bodyweight. It diffuses well across serous membranes and inflamed meninges. Vancomycin is excreted by the kidneys and is not removed by dialysis. The aminoglycosides continue to serve a useful role in the treatment of gram-negative, enterococcal and mycobacterial infections. Their volume of distribution approximates extracellular space. These drugs are also excreted renally and are removed by haemodialysis. Passage across the blood-brain barrier is poor, even in the face of meningeal inflammation. Low pH found in abscess conditions impairs function. Toxicity needs to be considered. Macrolide antibacterials are frequently used in the treatment of respiratory infections. Parenteral erythromycin can cause phlebitis, which limits its use. Parenteral azithromycin is better tolerated but paediatric pharmacokinetic data are lacking. Clindamycin is frequently used when anaerobic infections are suspected. Good oral absorption makes it a good choice for step-down therapy in intra-abdominal and skeletal infections. The use of quinolones in paediatrics has been restricted and most information available is in cystic fibrosis patients. High oral bioavailability is also important for step-down therapy. Amphotericin B has been the cornerstone of antifungal treatment in hospitalised patients. Its metabolism is poorly understood. The half-life increases with time and can be as long as 15 days after prolonged therapy. Oral absorption is poor. The azole antifungals are being used increasingly. Fluconazole is well tolerated, with high bioavailability and good penetration into the CSF. Itraconazole has greater activity against aspergillus, blastomycosis, histoplasmosis and sporotrichosis, although it's pharmacological and toxicity profiles are not as favourable.

Pharmacokinetics, excretion, and mass balance of liposomal amphotericin B (AmBisome) and amphotericin B deoxycholate in humans

The pharmacokinetics, excretion, and mass balance of liposomal amphotericin B (AmBisome) (liposomal AMB) and the conventional formulation, AMB deoxycholate (AMB-DOC), were compared in a phase IV, open-label, parallel study in healthy volunteers. After a single 2-h infusion of 2 mg of liposomal AMB/kg of body weight or 0.6 mg of AMB-DOC/kg, plasma, urine, and feces were collected for 168 h. The concentrations of AMB were determined by liquid chromatography tandem mass spectrometry (plasma, urine, feces) or high-performance liquid chromatography (HPLC) (plasma). Infusion-related side effects similar to those reported in patients, including nausea and back pain, were observed in both groups. Both formulations had triphasic plasma profiles with long terminal half-lives (liposomal AMB, 152 +/- 116 h; AMB-DOC, 127 +/- 30 h), but plasma concentrations were higher (P < 0.01) after administration of liposomal AMB (maximum concentration of drug in serum [C(max)], 22.9 +/- 10 microg/ml) than those of AMB-DOC (Cmax, 1.4 +/- 0.2 microg/ml). Liposomal AMB had a central compartment volume close to that of plasma (50 +/- 19 ml/kg) and a volume of distribution at steady state (Vss) (774 +/- 550 ml/kg) smaller than the Vss of AMB-DOC (1,807 +/- 239 ml/kg) (P < 0.01). Total clearances were similar (approximately 10 ml hr(-1) kg(-1)), but renal and fecal clearances of liposomal AMB were 10-fold lower than those of AMB-DOC (P < 0.01). Two-thirds of the AMB-DOC was excreted unchanged in the urine (20.6%) and feces (42.5%) with >90% accounted for in mass balance calculations at 1 week, suggesting that metabolism plays at most a minor role in AMB elimination. In contrast, <10% of the liposomal AMB was excreted unchanged. No metabolites were observed by HPLC or mass spectrometry. In comparison to AMB-DOC, liposomal AMB produced higher plasma exposures and lower volumes of distribution and markedly decreased the excretion of unchanged drug in urine and feces. Thus, liposomal AMB significantly alters the excretion and mass balance of AMB. The ability of liposomes to sequester drugs in circulating liposomes and within deep tissue compartments may account for these differences.

Determination of amphotericin B in human plasma using solid-phase extraction and high-performance liquid chromatography

A rapid and selective HPLC method is described and validated for measuring amphotericin B (AB) in plasma. The procedure involves the solid phase extraction of AB from plasma by incorporating 1-amino-4-nitronaphthalene as an internal standard during the last elution step in extraction followed by HPLC analysis with UV detection at 407 nm. The chromatographic separation is achieved in less than 10 min on a reversed-phase C-18 column using acetonitrile-disodium edetate (20 mM) (45:55, v/v) at pH 5.0 as eluent. A linear response over the concentration range of 0.0100--2.00 microg ml(-1) is obtained having a detection limit of 0.00500 microg ml(-1) for AB. The mean extraction recovery is found to be 98.1+/-1.1% (n=15). The within-day and day-to-day R.S.D. were less than 2% (n=15) and 6.54% (n=45) respectively. This method is applied for quantifying AB trough levels in the plasma of cancer patients who have been on antifungal therapy with AmBisome. It can further be applied either for AB therapeutic monitoring or single/multiple pharmacokinetic analysis of AB in plasma.

[New lipid formulations of amphotericin B. Review of the literature]

INTRODUCTION

Amphotericin B (amB) remains the gold standard for treatment of invasive fungal infections. Lipid formulations of amB have been developed in an attempt to improve both efficacy and tolerability (especially renal toxicity): amB lipid complex (ABLC), liposomal amB (AmBisome), amB colloidal dispersion (ABCD) and amB in lipid emulsion (Intralipid). This review analyzes the data available in the literature.

CURRENT KNOWLEDGE AND KEY POINTS

ABLC, AmBisome and ABCD are effective in various fungal infections, including invasive aspergillosis, systemic candidiasis, cryptococcal meningitis, mucormycosis and fusariosis. These formulations are also effective in persistent febrile neutropenia and in leishmaniosis. The three formulations show little renal toxicity and are safer than conventional amB in this respect. Preliminary data are available on amB in Intralipid: infusion-related adverse effects are reduced, but few data are available on efficacy in documented mycoses.

FUTURE PROSPECTS AND PROJECTS

Large-scale comparative clinical trials may clarify issues of relative efficacy in various forms of fungal infections.

A single high dose treatment of kala-azar with Ambisome (amphotericin B lipid complex): a pilot study

Thirty four patients with parasitologically confirmed visceral leishmaniasis were divided randomly into two groups of 17. Group A received Ambisome (amphotericin B lipid complex) at a dose of 15mg/kg body weight infused over 2h as a single dose; patients in group B received amphotericin B deoxycholate at a dose of 1mg/kg body infused for 2h for 20days. All 34 patients had a clinical, parasitological and ultimate cure. Ambisome was much better tolerated than amphotericin B, and adverse events were fewer in the Ambisome group. It was concluded that, if the cost of Ambisome were reduced, it would be a suitable first line drug. A longer study comparing three regimes of Ambisome: 15mg/kg body weight, 11mg/kg body weight and 7.5mg/kg body weight, should be undertaken.

A randomized, double-blind comparative trial evaluating the safety of liposomal amphotericin B versus amphotericin B lipid complex in the empirical treatment of febrile neutropenia. L Amph/ABLC Collaborative Study Group

In this double-blind study to compare safety of 2 lipid formulations of amphotericin B, neutropenic patients with unresolved fever after 3 days of antibacterial therapy were randomized (1:1:1) to receive amphotericin B lipid complex (ABLC) at a dose of 5 mg/kg/d (n=78), liposomal amphotericin B (L Amph) at a dose of 3 mg/kg/d (n=85), or L Amph at a dose of 5 mg/kg/d (n=81). L Amph (3 mg/kg/d and 5 mg/kg/d) had lower rates of fever (23.5% and 19.8% vs. 57.7% on day 1; P<.001), chills/rigors (18.8% and 23.5% vs. 79.5% on day 1; P<.001), nephrotoxicity (14.1% and 14.8% vs. 42.3%; P<.01), and toxicity-related discontinuations of therapy (12.9% and 12.3% vs. 32.1%; P=.004). After day 1, infusional reactions were less frequent with ABLC, but chills/rigors were still higher (21.0% and 24.3% vs. 50.7%; P<.001). Therapeutic success was similar in all 3 groups.

A pharmacokinetic study of amphotericin B lipid complex injection (Abelcet) in patients with definite or probable systemic fungal infections

This study describes a pharmacokinetic evaluation of amphotericin B (AMB) lipid complex injection (ABLC or Abelcet) in 17 patients with systemic fungal infection administered 5 mg/kg of body weight/day by infusion for 10 to 17 days. The results showed that AMB exhibited multiexponential disposition with high clearance, large volume of distribution at steady state, and long apparent elimination half-life but no evidence of accumulation in the blood after multiple daily doses. The results confirm previous observations and further reinforce the suggestion that ABLC may exist as a depot in the tissues from which free AMB is slowly released to limit exposure.

Amphotericin B colloidal dispersion

Amphotericin B colloidal dispersion (ABCD) is a colloidal dispersion of a stable complex of amphotericin B with cholesteryl sulphate in a 1:1 proportion, forming uniform disk-shaped particles. ABCD is associated with less nephrotoxicity than conventional amphotericin B deoxycholate. Infusion-related adverse events are more frequent in patients receiving ABCD than in patients receiving liposomal amphotericin B or amphotericin B deoxycholate. ABCD has been shown in a randomised, double-blind study, to be an effective alternative to amphotericin B deoxycholate for empirical treatment of patients with fever and neutropenia. ABCD is active in the treatment of invasive Candida spp. and Aspergillus spp. infections in immunocompromised hosts, however most of the data supporting its use for these types of infections is derived from non-comparative open-label clinical trials of patient refractory to or intolerant of conventional antifungal therapy. ABCD is approved by the US FDA for the treatment of invasive aspergillosis in patients where renal impairment of unacceptable toxicity precludes the use of amphotericin B deoxycholate in effective doses, and in patients with invasive aspergillosis where prior amphotericin B deoxycholate therapy has failed. Two other lipid formulations of amphotericin B, amphotericin B lipid complex and liposomal amphotericin B, are available and, like ABCD, are associated with reduced nephrotoxicity as compared to amphotericin B deoxycholate. The role of ABCD in comparison with these other lipid formulations of amphotericin B is discussed herein. High cost remains an issue with all lipid formulations of amphotericin B.

Amphotericin B and its new formulations: pharmacologic characteristics, clinical efficacy, and tolerability

Amphotericin B (amB) remains the gold standard for the treatment of invasive fungal infections. However, the efficacy is limited, with response rates from 10% to 80%. Moreover, amB is toxic, especially for the kidneys. New formulations have been developed in an attempt to improve both efficacy and tolerability. In an attempt to reduce toxicity, a number of investigators have reconstituted amB in a lipid emulsion, but few data are available on efficacy in documented infections. An improvement in immediate and renal tolerance was obtained with equivalent daily dose regimens, but the therapeutic index does not appear to be improved. This approach cannot be recommended at present. Three lipid formulations have been developed and are now available in most countries: amB colloidal dispersion (ABCD), amB lipid complex (ABLC), and liposomal amB (AmBisome). The efficacy of ABCD on various fungal infections has been assessed in open trials, with a response rate of 49% in aspergillosis, 70% in candidiasis, and 67% in mucormycosis. In two randomized trials comparing ABCD with amB in invasive aspergillosis and in persistent febrile neutropenia, the response rates were equivalent. ABCD was less nephrotoxic. In contrast, immediate reactions to ABCD were as frequent and severe as with amB. These immediate effects are more frequent during the first infusions and lessen as treatment continues. The recommended dose is 3-4 mg/kg/day. ABLC appeared to be effective as rescue therapy in various types of invasive mycoses, with a response rate of 42% in aspergillosis, 67% in candidiasis, and 82% in fusariosis. Efficacy identical to that of amB was demonstrated in a comparative randomized trial involving patients with invasive candidiasis. General and renal tolerability is improved compared with amB. The recommended dose regimen is 5 mg/kg/day. Liposomal amB (AmBisome) is the only truly liposomal formulation. The response rates in preliminary trials were 66% in aspergillosis and 81% in candidiasis. Several comparative studies have confirmed that this formulation has similar or superior efficacy relative to amB in various fungal infections and also in the empirical treatment of febrile neutropenia. Renal and general tolerability is excellent. The optimal dosing remains unclear but is generally between 3 and 5 mg/kg/day. A double-blind trial comparing the tolerance of liposomal amB and ABLC demonstrated that both infusion-related events and nephrotoxicity were significantly lower for liposomal amB. In sum, the new lipid formulations of amB are effective in various invasive fungal infections. The three formulations exhibit reduced nephrotoxicity compared with conventional amB. Large-scale comparative clinical trials may clarify issues of relative efficacy in various forms of mycotic infections.

Treatment of fungal infections in neutropenic children

Fungal infections have emerged as one of the most significant complications of antineoplastic therapy and marrow transplantation in children. Morbidity and mortality associated with fungal infections are high. Recent trends indicate that the incidence and spectrum of fungal infections are increasing, partly because of the increase in the number of children receiving intensive chemotherapy and marrow transplantation, but also because of the successful management of bacterial and viral infections. Though many factors may contribute to risk for developing a fungal infection, prolonged neutropenia is the most important. Until recently, options for antifungal therapy were limited. Advances include less toxic formulations of amphotericin B and an expanding armamentarium of azoles as well as new antifungal compounds. This review addresses the therapeutic options available for treatment of fungal infections in immunocompromised children.

Antifungal agents. Part I. Amphotericin B preparations and flucytosine

Traditionally, amphotericin B has been the cornerstone of antifungal treatment. Toxicity, however, is a major dose-limiting factor of amphotericin B deoxycholate. Nevertheless, it continues to have a major role in the treatment of deep-seated mycotic infections. Recently, less nephrotic lipid formulations, including amphotericin B lipid complex, amphotericin B cholesteryl sulfate, and liposomal amphotericin B, have been introduced. The pharmacologic properties, main indications, recommended dosages, related costs, and adverse effects of these various preparations are summarized in this review. Orally administered flucytosine is useful in certain infections, particularly cryptococcal meningitis, but it should be used with caution in patients with renal insufficiency.

Amphotericin B in lipid emulsion: stability, compatibility, and in vitro antifungal activity

Newer formulations of amphotericin B (AmB) complexed with liposomes or lipid suspensions have been developed. Preliminary studies have suggested that AmB in Intralipid (IL) may be as effective as, but less toxic than, conventional formulations of AmB, but few data are available regarding its stability, compatibility, or in vitro antifungal activity. A compatibility study was done to evaluate the effects of AmB concentrations in IL containing either 10 or 20% soybean oil. The effects of temperature, shaking, and AmB and IL concentrations on the stability of AmB-IL suspensions were analyzed by visual inspection and liquid chromatography. The in vitro antifungal activity of AmB-IL, compared to that of AmB alone against reference strains of Candida species was determined by using a broth macrodilution method in accordance with National Committee for Clinical Laboratory Standards guidelines (M27-T). Samples of AmB-IL which were lightly shaken retained more than 90% of the AmB concentration over 21 days when stored at either 4 or 23 degrees C. Varying the AmB concentration did not appear to affect the stability of AmB-IL. However, a precipitate was formed when mixtures with more than 30% lipid as a proportion of the total volume were centrifuged. AmB-IL and AmB alone had similar in vitro antifungal activities against reference strains of yeasts. Further pharmacologic and clinical studies with AmB-IL are warranted, although AmB should not be combined with IL in concentrations capable of producing a precipitate.

Amphotericin B lipid complex

OBJECTIVE

To evaluate the published data on the effectiveness and safety of amphotericin B lipid complex (ABLC) for the treatment of invasive mycosis and to evaluate data describing the pharmacologic properties and pharmacokinetic behavior of ABLC in both animals and humans.

DATA SOURCE

A MEDLINE search was conducted to identify literature published from 1965 to January 1997 for amphotericin B deoxycholate (DCAB) and ABLC. In addition, preliminary data published as abstracts and presented at national conferences on infectious disease and hematology within the last 6 years were also included in this review.

STUDY SELECTION

Both human and animal studies were reviewed. Animal and in vitro studies were selected to evaluate the pharmacologic and toxicologic properties of ABLC. For the evaluation of the efficacy, safety, and pharmacokinetic behavior of ABLC, large, well-controlled studies were reviewed. In addition, data from open-label and emergency use protocols were also included in the review.

DATA EXTRACTION

The study and analytical methods, results, and conclusions of the selected studies were evaluated. Pharmacokinetic data for both ABLC and DCAB that were derived from human subjects were also evaluated.

DATA SYNTHESIS

DCAB has been the cornerstone for the treatment of invasive mycosis, even though it has a narrow therapeutic index. Infusion-related toxicities (e.g., fever, chills, rigors) are likely due to DCAB stimulation of cytokine and prostaglandin synthesis. Conversely, nephrotoxicity, the primary non-infusion-related toxicity, likely results from the nonselective cytotoxic interaction between DCAB and cholesterol-containing mammalian cells. ABLC represents a new approach to improving the therapeutic index of DCAB. Mammalian cytotoxicity is attenuated by complexing amphotericin B to a mixture of phospholipids. This alters the affinity of amphotericin B and decreases its selective transfer from the complex to cholesterol-containing mammalian cells. Fungi also possess lipase, which improves the selective transfer from the complex to ergosterol-containing cell membranes. In humans, the lipid formulation increases the volume of distribution of amphotericin B. Thus, compared with DCAB, larger doses of ABLC can be administered for a longer duration with less nephrotoxicity. However, the prevalence of infusion-related toxicities associated with ABLC is similar to that of DCAB. Whether the alteration in distribution improves efficacy by improving tissue concentrations of amphotericin B has not been determined. The cost of this agent will limit its use.

CONCLUSIONS

ABLC has been shown to be at least as effective as DCAB, and it has been well tolerated in the clinical studies to date. Despite large dosages and extended courses of administration, there is little nephrotoxicity associated with its use. However, the cost of this agent will limit its use to the treatment of refractory mycosis or to cases where DCAB is contraindicated due to significant renal insufficiency.

Safety, tolerance, and pharmacokinetics of amphotericin B lipid complex in children with hepatosplenic candidiasis

The safety, tolerance, and pharmacokinetics of amphotericin B lipid complex (ABLC) were studied in a cohort of pediatric cancer patients. Six children with hepatosplenic candidiasis (HSC) received 2.5 mg of ABLC/kg of body weight/day for 6 weeks for a total dosage of 105 mg/kg. Mean serum creatinine (0.85 +/- 0.12 mg/dl at baseline) was stable at the end of therapy at 0.85 +/- 0.18 mg/dl and at 1-month follow-up at 0.72 +/- 0.12 mg/dl. There was no increase in hepatic transaminases. Mean plasma concentrations over the dosing interval (C(ave)) and area under the curve from 0 to 24 h (AUC(0-24h)) increased between the first and seventh doses but were similar between doses 7 and 42, suggesting that steady state was achieved by day 7 of therapy. Following the final (42nd) dose of ABLC, mean AUC(0-24h) was 11.9 +/- 2.6 microg h/ml, C(ave) was 0.50 +/- 0.11 microg/ml, maximum concentration of the drug in whole blood was 1.69 +/- 0.75 microg/ml, and clearance was 3.64 +/- 0.78 ml/min/kg. Response of hepatic and splenic lesions was monitored by serial computerized tomographic and magnetic resonance imaging scans. The five evaluable patients responded to ABLC with complete or partial resolution of physical findings and of lesions of HSC. During the course of ABLC infusions and follow-up, there was no progression of HSC, breakthrough fungemia, or posttherapy recurrence. Hepatic lesions continued to resolve after the completion of administration of ABLC. Thus, ABLC administered in multiple doses to children was safe, was characterized by a steady state attainable within 1 week of therapy, and was effective in treatment of HSC.

Behavior of amphotericin B lipid complex in plasma in vitro and in the circulation of rats

Amphotericin B lipid complex (ABLC) shows reduced toxicity relative to that of amphotericin B deoxycholate (AmB-d) while maintaining antifungal activity. Rat blood or plasma was spiked with ABLC in vitro. Released amphotericin B was separated from the parent material by centrifugation. At early times (0 to 15 min) most (approximately 90%) of the amphotericin B was complexed. The amount of released amphotericin B increased gradually in a time- and temperature-dependent fashion. The released amphotericin B was associated with plasma lipoprotein and nonlipoprotein proteins. The area under the concentration-time curve from 0 to 24 h for total amphotericin B in whole blood of rats given a single intravenous bolus dose of 1 mg of ABLC per kg of body weight was fourfold lower than that in rats given 1 mg of AmB-d per kg. The complexed amphotericin B was rapidly removed from the circulation and was distributed to the tissues in these rats. Other rats were treated intravenously with ABLC (10 mg/kg/day) or AmB-d (0.5 mg/kg/day) daily for 15 days. Blood was collected at 15 and 180 min after administration of the last dose. The total levels of amphotericin B in the blood of the group given ABLC were about three to five times those in the group given AmB-d, and the concentration of released, protein-bound amphotericin B in the plasma of the group given ABLC was about one to two times that observed for the group given AmB-d, despite the 20-fold difference in dose. The relative protein distribution of amphotericin B in plasma was similar after ABLC or AmB-d administration under these steady-state conditions in vivo. The rapid uptake of complexed amphotericin B by tissues and the very low levels of circulating protein-bound amphotericin B in plasma after the administration of ABLC may explain, in part, the reduced toxicity and enhanced therapeutic index of this preparation.

Diversity of lipid-based polyene formulations and their behavior in biological systems

Patients with cancer and infectious disease often display dyslipidemias that result in changes in their plasma lipoprotein-lipid composition. It is likely that the interactions of liposomal polyenes with plasma lipoproteins may be responsible for the far different pharmacokinetics and pharmacodynamics of these compounds when they are administered to infected patients rather than to animals or healthy volunteers. Amphotericin B (AmpB) and nystatin are examples of such polyenes. Amphotericin B initially distributes with the high-density lipoprotein (HDL) fraction upon incubation in plasma. Over time, AmpB redistributes from HDLs to low-density lipoproteins (LDLs). This redistribution appears to be regulated by lipid transfer protein. However, when AmpB is incorporated into liposomes composed of negatively or positively charged phospholipids, not only is the capability of LTP to transfer AmpB from HDL to LDL diminished, but AmpB remains retained with only the HDL fraction. However, when liposomal nystatin is incubated in plasma, over 50% of nystatin distributes with HDLs. Over time, nystatin redistributes from HDL to the lipoprotein-deficient plasma fraction, which is composed of mainly aqueous plasma proteins. The lipid composition selected for the drug appears to be a vital constituent in regulating the drug's interaction with biological fluids. Furthermore, liposome (or liposomal particle) size, fluidity, and other physiochemical characteristics also play a role in altering the pharmacokinetics and pharmacological effects of lipid-based drug formulations. Armed with this understanding, a rational approach to clinical development of these formulations could be facilitated.

[Amphotericin B deoxycholate (Fungizone): old drug, new versions]

Amphotericin B-deoxycholate (Fungizone) remains the main treatment of systemic mycoses. However, its toxicity, especially renal impairment, limits its use. The chemical properties of this molecule led to its association with lipidic structures. Among the three so-called liposomal formulations of amphotericin B, only one (AmBisome) is a true liposome. Its tolerance is good, along with high blood concentrations. The two others formulations, either in disk or ribbon form, are not true liposomes and these formulations are not as well tolerated as the former. These three forms of amphotericin are very expensive, thus limiting their use. The association of amphotericin B with other lipidic structures is of great interest. The direct solubilization of Fungizone in an emulsion (Intralipid 20%) is inexpensive and easily prepared extemporaneously; this preparation of Fungizone leads to a strong reduction of side effects and its efficacy is at least equivalent to conventional Fungizone. In the future, the association with triglycerides or lecithins is probable: possibly providing promising formulations.

Carrier effects on biological activity of amphotericin B

Amphotericin B (AmB), the drug of choice for the treatment of most systemic fungal infections, is marketed under the trademark Fungizone, as an AmB-deoxycholate complex suitable for intravenous administration. The association between AmB and deoxycholate is relatively weak; therefore, dissociation occurs in the blood. The drug itself interacts with both mammalian and fungal cell membranes to damage cells, but the greater susceptibility of fungal cells to its effects forms the basis for its clinical usefulness. The ability of the drug to form stable complexes with lipids has allowed the development of new formulations of AmB based on this property. Several lipid-based formulations of the drug which are more selective in damaging fungal or parasitic cells than mammalian cells and some of which also have a better therapeutic index than Fungizone have been developed. In vitro investigations have led to the conclusion that the increase in selectivity observed is due to the selective transfer of AmB from lipid complexes to fungal cells or to the higher thermodynamic stability of lipid formulations. Association with lipids modulates AmB binding to lipoproteins in vivo, thus influencing tissue distribution and toxicity. For example, lipid complexes of AmB can be internalized by macrophages, and the macrophages then serve as a reservoir for the drug. Furthermore, stable AmB-lipid complexes are much less toxic to the host than Fungizone and can therefore be administered in higher doses. Experimentally, the efficacy of AmB-lipid formulations compared with Fungizone depends on the animal model used. Improved therapeutic indices for AmB-lipid formations have been demonstrated in clinical trials, but the definitive trials leading to the selection of an optimal formulation and therapeutic regimen have not been done.

Comparison of three treatment regimens with liposomal amphotericin B (AmBisome) for visceral leishmaniasis in India: a randomized dose-finding study

The efficacy and safety of 3 regimens of liposomal amphotericin B (AmBisome) in the treatment of Indian visceral leishmaniasis were compared in a prospective open randomized trial. Thirty parasitologically confirmed patients were randomly divided into 3 equal treatment groups; group 1 received AmBisome 2mg/kg on days 1, 2, 3, 4, 5, 6, and 10 (total dose 14 mg/kg); group 2 received AmBisome 2 mg/kg on days 1, 2, 3, 4, and 10 (total dose 10 mg/kg); group 3 received the same dosage on 1, 5 and 10 (total dose 6 mg/kg). Clinical cure resulted in all patients by day 24. Haemoglobin, white blood cell count, body weight and serum albumin level improved on day 24 and became normal by day 180. No patient relapsed within 12 months of follow-up. Side effects were minimal. One patient in group 2 died after 2 months from an unrelated disease. Liposomal amphotericin B is a promising new drug which is highly efficacious in the treatment of Indian kala-azar and produces minimal toxicity.

Pharmacokinetics of conventional formulation versus fat emulsion formulation of amphotericin B in a group of patients with neutropenia

The pharmacokinetics of amphotericin B administered in a conventional 5% dextrose (glucose) (5% D) solution and in a 20% fat emulsion formulation (Intralipid; 20% IL) were compared in 16 patients (mean age, 42 years [range, 18 to 70 years]) who had been hospitalized for hematological malignancies and with proven or suspected fungal infections. All of the patients received 50 mg (approximately 1 mg/kg of body weight per day) of amphotericin B daily in random order, either as a 50-ml lipid emulsion (20% IL) (group I) or in 500 ml of 5% D (group II). Five serum samples were taken during the 24 h after drug administration, and the levels of amphotericin B were measured by high-pressure liquid chromatography. Serum amphotericin B concentrations declined rapidly during the first 6 h, and subsequent measurements revealed a slow terminal elimination phase in both groups. The maximum serum amphotericin B concentration was significantly lower when the drug was administered in 20% IL (1.46 +/- 0.61 versus 2.83 +/- 1.17 micrograms/ml; P = 0.02). The area under the concentration-time curve from 0 to 24 h was also much lower in group I (17.22 +/- 11.15 versus 28.98 +/- 15.46 micrograms.h/ml). The half-life of the distribution phase was approximately three times longer in group I (2.92 +/- 2.34 h versus 0.64 +/- 0.24 h; P = 0.011). Conversely, the half-lives of the elimination phase were approximately equal in the two groups (11.44 +/- 5.18 versus 15.23 +/- 5.25 h). The mean residence times were also similar in both groups (19.41 +/- 11.13 versus 19.65 +/- 7.86 h). The clearance and the steady-state volume of distribution of amphotericin B in group I were about twice as great as those in group II (62.97 +/- 35.51 versus 33.01 +/- 14.33 ml/kg/h and 1,043.92 +/- 512.10 versus 562.32 +/- 152.05 ml/kg [P = 0.034], respectively). Finally, the volume of distribution in the central compartment was greater in group I than in group II (618.17 +/- 231.80 versus 328.19 +/- 151.71 ml/kg; P = 0.013), but there were no differences in the volume of distribution in the peripheral compartment (425.75 +/- 352.87 versus 234.14 +/- 75.92 ml/kg). These results suggest that amphotericin B has a different pharmacokinetic profile when it is administered in 20% IL than when it is administered in the standard 5% D form and that the main difference is due to a clear-cut difference in the steady-state volume of distribution, especially that in the central compartment.