Intravenous foscarnet is effective for CMV retinitis, including ganciclovir-resistant infections, other types of CMV infection, and acyclovir-resistant HSV and VZV infections. Foscarnet is poorly soluble in aqueous solutions and requires large volumes for administration.
In CMV retinitis in AIDS patients, foscarnet (60 mg/kg every 8 hours or 90 mg/kg every 12 hours for 14-21 days followed by chronic maintenance at 90-120 mg/kg every day in one dose) is associated with clinical stabilization in ~90% of patients. A comparison of foscarnet with ganciclovir in AIDS patients found comparable control of CMV retinitis but improved overall survival in the foscarnet-treated group, possibly related to the drug's intrinsic anti-HIVactivity. Patients discontinue foscarnet because of side effects over three times as often as ganciclovir. A combination of foscarnet and ganciclovir is more effective than either drug alone in refractory retinitis; combinations may be useful in treating ganciclovir-resistant CMV infections in solid-organ transplant patients. Foscarnet benefits other CMV syndromes in AIDS or transplant patients but is ineffective as monotherapy in treating CMV pneumonia in bone marrow transplant patients. When used for preemptive therapy of CMVviremia in bone marrow transplant recipients, foscarnet (60 mg/kg every 12 hours for 2 weeks followed by 90 mg/kg daily for 2 weeks) is as effective as intravenous ganciclovir with less neutropenia. Foscarnet may reduce the risk of Kaposi's sarcoma in HIV-infected patients. Intravitreal injections also are used.
In acyclovir-resistant mucocutaneous HSV infections, lower doses of foscarnet (40 mg/kg every 8 hours for 7 days or longer) are associated with cessation of viral shedding and complete healing of lesions in ~75% of patients. Foscarnet also appears to be effective in acyclovir-resist-ant VZV infections. Topical foscarnet cream may be useful in chronic acyclovir-resistant infections in immunocompromised patients.
Ganciclovir and Valganciclovir chemistry and antiviral activity Ganciclovir (9-[1,3-dihydroxy-2-propoxymethyl] guanine) is an acyclic guanine nucleoside analog that is similar in structure to
h2n n xh2ochch2oh
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