Why must acyclovir dosing be adjusted for renal function in HSV encephalitis?

Why must acyclovir dosing be adjusted for renal function in HSV encephalitis?

• A. To ensure the drug achieves peak concentrations quickly
• B. To prevent drug accumulation and toxicity
• C. To enhance urinary excretion of the drug
• D. It is not necessary to adjust

Answer: (B)

Renal clearance controls how quickly acyclovir is removed from the body. In HSV encephalitis we use high-dose IV acyclovir to reach therapeutic levels in the CNS quickly, but if kidney function is impaired, the drug is cleared more slowly, causing drug levels to rise and potentially accumulate. This increases the risk of nephrotoxicity (like crystal-induced kidney injury) and CNS toxicity (confusion, tremor, seizures). So dosing must be adjusted based on renal function to maintain effective antiviral exposure without letting levels become toxic. Hydration and appropriate infusion rates help reduce kidney precipitation. The goal isn’t to push peak concentrations higher or to increase urinary excretion; it’s to prevent drug accumulation by matching dose to the patient’s kidney function.

Renal clearance controls how quickly acyclovir is removed from the body. In HSV encephalitis we use high-dose IV acyclovir to reach therapeutic levels in the CNS quickly, but if kidney function is impaired, the drug is cleared more slowly, causing drug levels to rise and potentially accumulate. This increases the risk of nephrotoxicity (like crystal-induced kidney injury) and CNS toxicity (confusion, tremor, seizures). So dosing must be adjusted based on renal function to maintain effective antiviral exposure without letting levels become toxic. Hydration and appropriate infusion rates help reduce kidney precipitation. The goal isn’t to push peak concentrations higher or to increase urinary excretion; it’s to prevent drug accumulation by matching dose to the patient’s kidney function.