ATC classificationPharmacotherapeutic group: Antimycotics for systemic use, antibiotics; ATC code: J02AA01.
Mode of actionAmphotericin B is a macrocyclic, polyene antifungal antibiotic produced by Streptomyces nodosus. Amphotericin B is fungistatic or fungicidal depending on the concentration attained in body fluids and the susceptibility of the fungus. The drug is thought to act by binding to sterols in the fungal cell membrane, with a resulting change in membrane permeability, allowing leakage of a variety of small molecules.Mammalian cell membranes also contain sterols, and it has been suggested that the damage to human cells and fungal cells caused by amphotericin B may share common mechanisms. The lipophilic moiety of amphotericin allows the drug to be integrated into the lipid bilayer of the liposomes. Liposomes are closed, spherical vesicles formed from a variety of amphiphilic substances such as phospholipids.Phospholipids arrange themselves into membrane bilayers when exposed to aqueous solutions.PK/PD relationship Mechanism of resistance Intrinsic resistance, though rare, maybe primarily due to decrease in ergosterol or a change in the target lipid; Leading to reduced binding of amphotericin B to the cell membrane.Breakpoints EUCAST breakpoints for AmBisome have not yet been established, however, susceptibility to AmBisome may differ to that of amphotericin B deoxycholate.Amphotericin B, the antifungal component of AmBisome is active in vitro against many species of fungi., most strains of Histoplasma capsulatum, Coccidioides immitis, Candida spp, Blastomyces dermatidis, Rhodotorula, Cryptococcus neoformans, Sporothrix schenkii and Aspergillus fumigatus, Penicillium marneffi, and members of the mucormycetes group of moulds including Mucor mucedo, Rhizomucor and Rhizopus oryzae.The majority of clinically important fungal species seem to be susceptible to Amphotericin B, although intrinsic resistance has rarely been reported for example, for some strains of S. schenckii, C. glabrata, C.krusei, C. tropicalis, C. lusitaniae, C parapsilosis and Aspergillus terreus.AmBisome has been shown to be effective in animal models of visceral leishmaniasis (caused by Leishmania infantum and Leishmania donovani).Clinical Experience The efficacy of AmBisome has been established in a number of clinical trials for the treatment of systemic mycotic infections, as empirical therapy for fever of unknown origin in neutropenic patients and for the treatment of visceral leishmaniasis. These studies include comparative randomized studies of AmBisome versus conventional amphotericin B in confirmed Aspergillus and Candida infections where the efficacy of both medicinal products was equivalent. In both adult and paediatric febrile neutropenic patients presumed to have fungal infection, the results of a randomized, double-blind clinical trial demonstrated that AmBisome administered at 3 mg/kg/day is as effective as conventional amphotericin B. The efficacy of AmBisome in the treatment of visceral leishmaniasis has been clearly demonstrated in a large population of immunocompetent and immunocompromised patients.Invasive Filamentous Fungal Infections (IFFI) including Aspergillus spp.: The efficacy of AmBisome has been demonstrated in a prospective, randomised, multicentre study as first line treatment in immunocompromised, mainly neutropenic adults and children (> 30 days old) with proven or probable IFFIs (AmBiLoad Study).Patients were monitored for 12 weeks. A standard-dose regimen of 3 mg/kg/day (N=107) was compared to a loading dose regimen of 10 mg/kg/day (N=94) for the first 14 days of treatment. The favourable overall response rates were 50% of subjects in the standard-dose group and 46% of the subjects in the loading-dose group in the modified intent-to-treat analysis set. Differences were not statistically significant. The median time to resolution of fever was similar in the standard-dose and loading-dose groups (6 and 5 days, respectively). Twelve weeks after the first dose of AmBisome, survival was 72% in the standard-dose group and 59% in the loading-dose group, a difference that was not statistically significant.Invasive candidiasis: AmBisome (3 mg/kg/day) was as effective as Micafungin (100 mg/day [Body weight > 40 kg] or 2 mg/kg/day [Body weight ≤ 40 kg]) as first line treatment of candidaemia and invasive candidiasis in a randomised, double-blind, multinational non-inferiority study in adults and children. AmBisome and Micafungin were administered for a median duration of 15 days. The favourable overall response was 89.5% (170/190) in the AmBisome group and 89.6% (181/202) in the Micafungin group (per protocol analysis set). The paediatric sub-study, which enrolled 98 patients of whom 57 were <2 years old, (including 19 premature infants), showed favourable overall response rates of: 88.1% (37/42) for AmBisome and 85.4% (35/41) for Micafungin (per protocol analysis set).Invasive zygomycosis: A retrospective analysis covering a 15-year period included 59 patients with haematological malignancies with proven or probable mucormycosis.Therapy was successful in 16 patients (37%): 9 of 39 patients who received conventional amphotericin B (23%) and 7 of the 12 patients who received AmBisome (58%) responded to therapy.