Cytomegalovirus (CMV) infection is the most important cause of mental retardation and sensorineural hearing loss. Antiviral treatment with valganciclovir, a relatively new but potential toxic oral drug, is recommended to prevent further hearing deterioration. In this retrospective cohort study we evaluated the relation between the dose of valganciclovir and the reduction of CMV viral load, as well as the toxicity. All neonates with gestational age <32 weeks with CMV infection treated with oral

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... alganciclovir (30 mg/kg/day) were included. Time interval to reach CMV viral load below detection level (<250 copies/ml) was determined. Toxicity was measured by plasma trough levels, thrombocytopenia and leukopenia. Data of 6 infants, median gestational age 252 weeks, were analyzed. Time interval between start of therapy and viral load below detection level was 25 -54 days. In total, 37 through plasma samples were analyzed. Of these, 28 were in the normal range, 3 above and 6 under the target concentration. Mild transient leukopenia occurred in 1 infant. No thrombocytopenia occurred. Conclusion: Antiviral treatment of CMV infection with oral valganciclovir results in adequate plasma through levels. Also, a progressive reduction of viral load in the urine below detection level was reached within 25 -54 days, without serious short time side effects.