Amphotericin B Cannot Be Given Orally for Systemic Infections
Amphotericin B is NOT administered orally for the treatment of systemic fungal infections—it must be given intravenously. The FDA-approved formulations are exclusively for intravenous administration, and oral amphotericin B is not absorbed systemically from the gastrointestinal tract 1.
Why Oral Administration Doesn't Work
The physicochemical properties of amphotericin B prevent adequate absorption from the GI tract. The drug label explicitly states that amphotericin B should be "administered intravenously under close clinical observation" 1. All FDA-approved formulations (amphotericin B deoxycholate, liposomal amphotericin B, and amphotericin B lipid complex) are designed for IV use only 1.
Clinical Guidelines Confirm IV-Only Administration
Multiple high-quality guidelines consistently specify intravenous routes:
- For histoplasmosis: Amphotericin B formulations are used IV for severe pulmonary or disseminated disease, with typical dosing of 0.5-1.0 mg/kg IV daily 2
- For cryptococcal meningitis: Amphotericin B 0.7-1.0 mg/kg IV daily (or liposomal formulation 3-6 mg/kg IV daily) is standard 3
- For coccidioidomycosis: Amphotericin B 0.5-1.0 mg/kg IV once daily until clinical improvement 3
- For invasive candidiasis: Amphotericin B 0.5-1.5 mg/kg IV once daily 3
The Exception: Topical/Local Use Only
The only scenario where amphotericin B can be given "orally" is for local, non-systemic infections:
- Oral thrush (oropharyngeal candidiasis): Amphotericin B oral suspension 1 mL (100 mg/mL) 4 times daily can be used as a topical treatment that acts locally in the mouth 3
- This formulation is swished and swallowed but provides only local antifungal activity—it does NOT treat systemic infections
The FDA label explicitly warns that amphotericin B "should not be used to treat noninvasive forms of fungal disease such as oral thrush, vaginal candidiasis and esophageal candidiasis in patients with normal neutrophil counts" when referring to the IV formulation 1.
Experimental Oral Formulations (Not Yet Available)
Recent research has explored novel oral delivery systems for amphotericin B, including:
- Lipid nanocrystal formulations showing promise in clinical trials for cryptococcal meningitis 4
- Fatty acid conjugates and carbon nanotube carriers 5, 6
- Amorphous solid dispersions 7
However, none of these are FDA-approved or commercially available. The 2023 lipid nanocrystal trial showed comparable efficacy to IV amphotericin but remains investigational 4.
Clinical Bottom Line
For any systemic fungal infection requiring amphotericin B therapy, you must use intravenous administration. The only oral use is amphotericin B oral suspension for topical treatment of oral candidiasis, which does not provide systemic antifungal coverage.