Why is acyclovir preferred to be given as an infusion over 60 minutes for a neonate with possible HSV encephalitis?

Acyclovir is preferred to be administered as an infusion over 60 minutes in neonates with possible HSV encephalitis primarily to reduce the risk of nephrotoxicity. Acyclovir is known to cause renal toxicity, particularly when administered too rapidly. This toxicity is associated with crystal formation in the renal tubules, which can lead to acute kidney injury. By infusing acyclovir over a longer period, the concentration of the drug in the bloodstream is kept at safer levels and decreases the risk of crystallization in the kidneys.

In neonates, whose renal function may not be fully mature, careful monitoring and administration of medications that have renal clearance is crucial. The slow infusion helps to maintain adequate hydration and allows the kidneys to handle the drug's clearance without overwhelming them.

The other options do not accurately reflect the primary consideration for the specific administration of acyclovir in this clinical context. Rapid therapeutic levels can often be achieved with a variety of administration techniques, and while easier administration might be a consideration in some scenarios, it does not address the critical aspect of safety related to nephrotoxicity. Allergic reactions to acyclovir are uncommon, and thus, preventing allergic reactions is not a primary concern in this specific administration protocol.