Cytomegalovirus (CMV), a major opportunistic viral pathogen frequently causing disease in immunocompromised patients such as organ transplant recipients and people with
AIDS, may present as
pneumonitis,
gastrointestinal disease, or
encephalitis. Its most common manifestation in patients with
AIDS is
retinitis which, if left untreated, invariably progresses to extensive
retinal necrosis and ultimately to
blindness.
Ganciclovir sodium, currently the only licensed
antiviral agent for the treatment of CMV
retinitis, effectively controls this
infection in a majority of
AIDS patients, but significant
granulocytopenia or
thrombocytopenia related to
ganciclovir therapy often limit its clinical application. Myelosuppression may be further exacerbated in
AIDS patients by such other agents as
zidovudine or
trimethoprim/sulfamethoxazole, often necessitating dosage reductions or discontinuation of these agents in patients receiving
ganciclovir.
Foscarnet sodium, a
pyrophosphate analog active against both cytomegalovirus and the human immunodeficiency virus type 1 (HIV), may be an effective alternative to
ganciclovir in the management of CMV
retinitis. Trials with intravenous
foscarnet in CMV
retinitis have reported favorable results using initial daily doses of 180-230 mg/kg/d given as intermittent infusions every eight hours, followed by maintenance regimens of 60-90 mg/kg/d given as single daily one- or two-hour infusions.
Foscarnet therapy may result in renal impairment, and indefinite intravenous maintenance
therapy may be required to prevent recurrence of CMV
infection. Despite these drawbacks,
foscarnet's lack of major myelosuppressive toxicity, and its activity in suppressing HIV replication, make this a potentially safe and effective alternative agent for the management of CMV
infection, especially in
AIDS patients.