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Antifungal-Drugs
lecture 34 goodman
| Question | Answer |
|---|---|
| azole type antifungal agent mechanism | inhibit the P450 lanosterol 14alpha-demethylase, methylated ergosterol destabilizes fungal CMs causing lysis, toxic levels of lanosterol |
| polyene type antifungal agent mechanism | one end binds to endogenous ergosterol while the polyhydroxyl end creates an aqueous channel that disrupts fluid/ion balance and kills cells |
| amphotericin B | broad-spectrum polyene type fungicidal drug, administered IV with very low therapeutic index, high protein-binding capacity, no CNS activity unless given intrathecally |
| adverse effects of amphotericin B | immediate: fever, chills, vomiting and H/A later: nephrotoxicity, acute renal failure requiring dialysis, sz with intrathecal administration |
| azole drugs: ketoconazole, fluconazole, itraconazole | taken orally, enhanced @ low pH and by food, no CSF penetration, inhibit P450 enzymes that are involved in steroid synthesis = low libido & gynecomastia |
| rifampin's effect on azoles | induces P450 enzymes and increases their rate of metabolism |
| ketoconazole | imidazole useful mostly for topical tx of fungal infections |
| fluconazole (Diflucan) | triazole is more powerful than imidazoles, good for systemic infections, IV or oral, widest therapeutic index, CSF penetration = good for fungal meningitis |
| itraconazole | most potent triazole; systemic hystoplasma, blastomyces and sporothrix, oral and esophageal candidiasis, little CSF penetration |
| triazoles have little effect on P450 enzymes | as compared to imidazoles (ketoconazole) |
| method of resistance for azole-type drugs | altered demethylase |
| flucytosine mechanism of action | metabolized by fungal cytosine deaminase to 5-FU, which is a potent thymidylate synthase inhibitor |
| flucytosine, other facts | absorbed almost completely to all compartments including CSF, bone marrow toxicity and BLOOD DYSCRASIAS like anemia and leukopenias; used in combo with amphotericin B for cryptococcal meningitis |
| echinocandin mechanism of action | competitive inhibitors of beta-1,3-D-glucan synthase aka blocks synthesis of glucans in cell walls of fungi |
| echinocandins, other facts | must be IV (poor absorption), fewer adverse effects and P450 interactions than the other types, active agents against Candida, Aspergillus and PCP |
| echinocandins are fungicidal to Candida, fungistatic for others | |
| caspofungin | echinocandin, significant drug interactions |
Created by:
sirprakes
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