A retrospective study was performed to collect information regarding efficacy 
and toxicity of cidofovir (CDV) in allogeneic stem cell transplant patients. 
Data were available on 82 patients. The indications for therapy were 
cytomegalovirus (CMV) disease in 20 patients, primary preemptive therapy in 24 
patients, and secondary preemptive therapy in 38 patients. Of the patients, 47 
had received previous antiviral therapy with ganciclovir, foscarnet, or both 
drugs. The dosage of CDV was 1 to 5 mg/kg per week followed by maintenance every 
other week in some patients. The duration of therapy ranged from 1 to 134 days 
(median, 22 days). All patients received probenecid and prehydration. Ten of 20 
(50%) patients who were treated for CMV disease (9 of 16 with pneumonia) 
responded to CDV therapy, as did 25 of 38 (66%) patients who had failed or 
relapsed after previous preemptive therapy and 15 of 24 (62%) patients in whom 
CDV was used as the primary preemptive therapy. Of the patients, 21 (25.6%) 
developed renal toxicity that remained after cessation of therapy in 12 
patients. Fifteen patients developed other toxicities that were potentially due 
to CDV or the concomitantly given probenecid. No toxicity was seen in 45 (61.6%) 
patients. Cidofovir can be considered as second-line therapy in patients with 
CMV disease failing previous antiviral therapy. However, additional studies are 
needed before CDV can be recommended for preemptive therapy.