Amphotericin B

Amphotericin B. Amphotericin B (3), an important polyene antibiotic, is administered almost exclusively via the intravenous route and is therefore discussed in more detail under the systemic antimycotics. The vaginal tablets contain 50 mg amphotericin B, and 100 mg tetracycline base per tablet (see also Antibiotics, tetracyclines). The tablets for oral use contain 50 mg amphotericin B, 250 mg tetracycline base, and 125 mg sodium hexametaphosphate. A combination ointment contains 1 mg fludrocortisone acetate, 2.5 mg neomycin, 0.25 mg gramicidin, and 1 g plastibase in addition to 30 mg amphotericin B (see also Antibiotics, peptides). 

Clotrimazole and other azole derivatives have a different mode of action than the polyenes, eg, amphotericin B. The latter biad to the ergosterol present ia the membranes of yeasts and fungi, but azole derivatives inhibit the cytochrome P-450 dependent biosynthesis of ergosterol (8—11). This inhibition not only results in a reduction of ergosterol, but also in an accumulation of C-14 methyl sterols. They disturb membrane permeabiUty, inhibit cell rephcation, and are basically responsible, in combination with the reduction of ergosterol levels, for the antifungal action. 

Potassium Iodide. When potassium iodide [7681-11-0] is adrninistered orally for several (6—8) weeks, a therapeutic effect may be obtained ia the subcutaneous form of sporotrichosis. Amphotericin B is used iatravenously to treat systemic sporotrichosis. The KI dosage is usually a saturated solution ia water (1 g/mL). The usual oral dose is 30 mg/kg/d. Children should receive five droplets, three times a day (after meals) the dose may be iacreased to 15—20 droplets. Side effects iaclude digestive disorders, swelling of the saUvary glands, and lacrimation. Thyroid function tests may be disturbed. 

A marked improvement is generally noted after 4—8 weeks of treatment. Treatment is often continued until a total dose of 3 g is reached. In the case of coccidioidomycosis, for example, treatment with 0.4—0.8 mg/kg/d may last months. The polyene is adrninistered intrathecaHy to treat Coccidioides meningitis. However, the results are only moderate. It is very important to check renal and hepatic function during treatment with amphotericin B. 

Ketoconazole. For treatment of systemic mycoses with amphotericin B or miconazole, the patient must be admitted to a hospital. This is not always possible, particularly in areas where systemic mycoses occur frequently, nor is it always desirable, because of the expense. For these reasons, it was desirable to find an antimycotic that combined safety and broad-spectmm activity with oral adraiinistration. Ketoconazole (10), which is orally active, met most of these requirements. This inhibitor of the ergosterol biosynthesis is an A/-substituted imidazole, that differs from its precursors by the presence of a dioxolane ring (6,7). Ketoconazole is rapidly absorbed in the digestive system after oral adrninistration. Sufficient gastric acid is required to dissolve the compound and for absorption. Therefore, medication that affects gastric acidity (for example, cimetidine and antacids) should not be combined with ketoconazole. 

Naeg/ena is treatable with intravenous amphotericin B (15, Fungizone), a toxic dmg that must be used with caution. 

A combination of amphotericin B, miconazole (16), and rifampin (17) was used to successfully cure one patient. In addition, tetracycline (7) and minocycline (18) have been recommended although their clinical efficacy have not been estabUshed. No proven therapeutic agents exist for treating A.catbamoeba infections, however, the phenothiazines, trifluoperazine [117-89-5] and chlorpromazine [50-53-3], show promise in vitro. 

Amphotericin B (15) is an antifimgal macioHde antibiotic produced by Streptomjces nodosus that has been used as an alternative, albeit more toxic, dmg to the antimonials. It acts as a leishmanicide against the visceral and mucocutaneous forms of the disease. To overcome its potentially severe nephrotoxicity, the dmg must be adrninistered over an extended period of time. 

Amoxicillin — see Penicillin, D-n-amino-p-hydroxybenzyl-Amozonolysis cycloalkenes, 6, 876 Amphotericin B antifungal agent veterinary use, 1, 211... 

III. Via newly formed pores maitotoxm, amphotericin B, chlordecone,... 

Properties, structure, and derivatives of macrocyclic polyenic lactone amphotericin B 97MI12. 

Streptomyces mycarofaciens Midecamycin Streptomyces nodosus Amphotericin B Streptomyces noursei Nystatin... 

The insolubility of amphotericin B (1) in common organic solvents necessitated the preparation of tractable intermediates that were more... 

A demonstration of the usefulness of this deglycosidation reaction in the preparation of amphotericin B aglycon derivatives is shown in Scheme 3. Exposure of amphotericin B derivatives 5ab to NBS and CaC03 in CCI4 results in the formation of heptaenones 6ab in 18-30% yield (two isomers) together with bicyclic system 7 (10%) and mycosamine derivative 8 (9%). 

The body of chemistry described above for amphotericin B (1) allowed, for the first time, the preparation of a series of novel derivatives of this polyene macrolide antibiotic and set the stage for a total synthesis of this target molecule. Below we unfold the adventure that led to the accomplishment of this goal.910... 

---