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The Disease: Candidiasis
Structure
Action
Toxicity
Distribution of flucytosine in the body


The Disease: Candidiasis

Candida Albicans is a yeast growth present in all of us normally controlled by bacteria in the intestines. However, when something destroys helpful bacteria, the yeast begins to invade and colonize the body tissues. These yeast colonies release powerful chemicals into the bloodstream. Some of the symptoms are lethargy, chronic diarrhea, yeast baginitis, bladder infections, muscle and join pain, menstrual problems, constipation and severe depression. The medical term for this yeast overgrowth is candidiasis.
This is not a new problem, but it is usually thought of as a minor fungal infection of the mucous membranes, skin and nails. But the increased and sometimes excessive use of antibiotics, birth control pills, and steroids will allow candidiasis to become a chronic, systemic infection that causes tissure damage throughout the body. Chemicals produced by the candida attack the immune system. if the immune system weakens, the candida will spread out into various body tissues and colonize. Candida is of particular importance in patients who are already immuno-supppressed diue to the presence of the HIV/AIDS virus.
Candida can be controlled by a number of factors, including diet. However, in extreme cases, a series of anti-fungal agents, such as Flucytosine(5-FC) are often prescribed, usually in conjunction with one or more other medications.

Structure

(Molecule rendered using Spartan)
The image to the left is a structural model of flucytosine. Each ball represents an atom and each wire represents a bond between the atoms. The grey atoms are carbon, blue atoms are nitrogen, red atoms are oxygen, white atoms are hydrogen, and green atoms are flourine. Below is a chemical structure of the flucytosine molecule, in the same form as the image to the left.

Action

5-FC is believed to act by interfering with RNA, DNA, and protein synthesis. When used alone, resistance devleops rapidly.

Toxicity

Entercolitis, nausea, vomiting, diarrhea, rash, anemia, leukopenia, thrombocytopenia, elevated liver enxymes, increase BUN or creatinine, CNS derangements. Toxicity is frequent when given with Amphotericin B; Amphotericin may increase the toxicity of 5-FC by interfering with renal excretion. Dose-dependent leukopenia, with or withou thrombocytopenia, can be fatal; it is more frequent when serum concentrations exceed 0.100 mg/ml.

Distribution of flucytosine in the body

Flucytosine is taken orally. From the intestines, the drug is absorbed into the plasma. From the plasma, the durg can either be filetered into the kidneys, from where it is eliminated through the urine, or it can move through the capillaries of the blood system into the extracellular spaces. This movement through the capillaries is vidirectional. From the extracellular spaces, the drug can pass through the cell wall or cell membrane into the intracellular space. Movement across the cell membrane is also bidirectional.
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