Amphotericin B is a polyene antifungal drug, often used intravenously for systemic fungal infections. Oral preparations of amphotericin B are used to treat thrush; these are virtually non-toxic, in contrast to typical intravenous therapy (IV) doses. One of the main intravenous uses is treating various systemic fungal infections, including cryptococcal meningitis. Amphotericin B is also commonly used in tissue culture to prevent fungi from contaminating cell cultures. Mammalian and fungal membranes both contain sterols, a primary membrane target for amphotericin B. Because mammalian and fungal membranes are similar in structure and composition, this is one mechanism by which amphotericin B causes cellular toxicity. Amphotericin B molecules can form pores in the host membrane as well as the fungal membrane.