Cytomegalovirus (CMV) infection is very common throughout the world, and has 
become more of a pediatric clinical concern given the high incidence of 
congenital CMV infections as well as the increasing numbers of immunocompromised 
patients. Because of this, the need for antiviral therapies in infants and 
neonates is growing. Currently, there are four antivirals available that are 
active against CMV: ganciclovir, valganciclovir, foscarnet, and cidofovir. At 
this time, none have approved indications for use in children. Although there 
are limited data regarding the dose, pharmacokinetics (PK), safety, and adverse 
events for some of these antivirals, ganciclovir, and its oral prodrug 
valganciclovir, have been the best studied in the infant and neonate 
populations. In general, pharmaceutical PK studies in young children are limited 
by the constraints of sampling difficulties and blood volume requirements; fewer 
sampling times and studies may be available for drug evaluation. Given this 
caveat, ganciclovir and valganciclovir PK in children thus far appears to follow 
a monocompartmental model, contrary to what has been described in adults. 
However, when normalized for weight, the volume of distribution, clearance, and 
half-life of ganciclovir are similar to those found in adults. Given the 
findings that ganciclovir (and thus valganciclovir) clearance is directly 
proportionate to renal function, care must be taken when administering the drug 
to patients with impaired renal function. Recent studies evaluating 
valganciclovir PK in infants (at a dose of 16 mg/kg every 12 hours) have shown 
similar areas under the plasma concentration-time curve (AUCs) to intravenous 
ganciclovir (at a dose of 6 mg/kg every 12 hours), and that these AUCs remain 
quite stable over a number of weeks. As seen in adults, oral ganciclovir has a 
low bioavailability (4.8% in a pediatric analysis) and is therefore a poor 
alternative for treating serious CMV infections. Neutropenia is the most 
frequent toxicity associated with ganciclovir and valganciclovir therapy, 
whereas significant (and possibly irreversible) renal toxicity can be seen with 
cidofovir. Foscarnet administration can also result in renal toxicity as well as 
significant electrolyte imbalances. Several of these drugs have potential 
toxicities that are of concern, including carcinogenesis, teratogenesis, and 
azospermia (ganciclovir, valganciclovir, and cidofovir) and deposition into bone 
or dentition (foscarnet) that may have significant implications when treating an 
infant. Given these potential ill effects, careful consideration of the 
indications for the clinical use of these antivirals is necessary before using 
them for CMV infection in neonates and infants.