Pentamidine Foscamet

Foscamet sodium should not be mixed with any intravenous infusion drug, since it interacts with glucose- and calcium-containing solutions and sodium, ganciclovir, certain antibacterials, amphotericin, pentamidine isethionate, and trimetrexate.18 Care must be taken to avoid inhalation and exposure of the skin to zalcitabine powder. 

Probenecid but not cidofovir alters zidovudine pharmacokinetics such that zidovudine doses should be reduced when probenecid is present, as should the doses of drugs similarly affected by probenecid fe.g., /i-lactam antibiotics, nonsteroidal anti-inflammatory drugs [NSAIDs], acyclovir, lorazepam, furosemide, methotrexate, theophylline, and rifampin). Concurrent nephrotoxic agents are contraindicated, and an interval of 1 week before beginning cidofovir treatment is recommended after prior exposure to aminoglycosides, intravenous pentamidine, amphotericin foscamet, NSAIDs, or contrast dye. Cidofovir and oral ganciclovir in combination are poorly tolerated at full doses. 

Foscamet is highly ionized at physiological pH, and metabolic abnormalities are very common, including increases or decreases in Ca and phosphate, hypomagnesemia, and hypokalemia. Concomitant intravenous pentamidine administration increases the risk of hypocalcemia. 

Foscamet sodium (Fig. 23.20) mimics pyrophosphate and inhibits the binding of nudeoside triphosphates to DNA polymerase. Thus it has a relatively broad spectrum of activity, but is used to treat CMV and herpes in AIDS patients. Since it has a different mode of action from dmgs such as addovir, it can be used in combination with them to increase the effectiveness of treatment. Since it forms insoluble salts with bases it is incompatible with basic drugs such as pentamidine and vancomydn, which may be used to treat secondary infections in AIDS. 

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