Depending on symptoms and other treatments that have been attempted, a doctor may prescribe a regimen of the antibiotic amphotericin B to be administered intravenously during hospitalization to treat an infected patient. The antibiotic amphotericin B effectively kills an invading microbe by interfering with the cell membrane function of sterols, causing holes to develop in the cell membrane which will lead to cell lysis and death. Due to the fact that bacteria have cell walls surrounding their cell membranes that typically are composed of peptidoglycan – a molecular combination of carbohydrate and protein subunits that protects the bacterial cell from osmotic lysis – and very rarely have sterols in their cell membranes, amphotericin B would not be used against a bacterial infection. Instead, it would be used against a systemic fungal infection. As eukaryotes, fungi contain sterols in their cell membranes to aid in maintaining cell membrane permeability despite temperature variations as well as to aid in the exchange of materials between the intracellular fluid and the extracellular environment. When the amphotericin B interacts with the sterols in the cell membrane, it effectively creates holes in the cell membrane. Not only will this allow for unregulated flow of materials both into and out of the cell, but it will also frequently will result in an excess of water being introduced into the cytoplasm of the cell; when the volume of water reaches a level too high for the area contained within the cell membrane, the cell will burst, or lyse, and die. Clinical studies have shown that amphotericin B has a greater affinity for, or attraction to, the ergosterol of the fungal cells than the cholesterol of the host (typically human in this case) cells, and so it is used more frequently than other anti-fungal treatments. There are, however, still side effects that both prescribing doctors and ill patients must be aware of when using amphotericin B. Possible side effects include, but are not limited to the following: thrombophlebitis; nephrotoxicity; fever; chills; and anemia. Thrombophlebitis occurs when a blood clot forms in a vein; it may occur in either superficial or deep veins and is typically quite painful. Nephrotoxicity refers to the inability of the kidney and its functional subunits, the nephrons, to function properly in the filtering of blood into urine. Anemia results due to a low red blood cell count, which results in a decreased ability to transport oxygen throughout the body. Due to the possible severity of these side effects, the therapeutic value of amphotericin must be carefully weighed before a regimen is began.