Comparative Pharmacology
Head-to-head clinical analysis: ACYCLOVIR SODIUM versus FOSCAVIR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: ACYCLOVIR SODIUM versus FOSCAVIR.
ACYCLOVIR SODIUM vs FOSCAVIR
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Acyclovir is a synthetic nucleoside analogue with activity against herpes simplex virus (HSV) types 1 and 2, and varicella-zoster virus (VZV). It is converted to acyclovir monophosphate by viral thymidine kinase, then further phosphorylated to acyclovir triphosphate, which competitively inhibits viral DNA polymerase and incorporates into viral DNA, causing chain termination.
Foscarnet is a pyrophosphate analog that selectively inhibits viral DNA polymerase and reverse transcriptase by binding to the pyrophosphate binding site, preventing the cleavage of pyrophosphate from deoxynucleotide triphosphates, thereby inhibiting viral DNA synthesis. It does not require activation by viral thymidine kinase, making it active against acyclovir-resistant HSV and VZV, and ganciclovir-resistant CMV.
Dosing is indication-specific. For herpes simplex encephalitis: 10 mg/kg IV every 8 hours for 10–14 days (adults and children ≥12 years) or 20 mg/kg IV every 8 hours (3 months–12 years). For severe genital herpes: 5 mg/kg IV every 8 hours for 5 days. For mucocutaneous HSV in immunocompromised: 5 mg/kg IV every 8 hours for 7–14 days. For varicella zoster in immunocompromised: 10 mg/kg IV every 8 hours for 7 days. For neonatal HSV: 20 mg/kg IV every 8 hours for 14–21 days (disseminated/CNS) or 14 days (skin/eyes/mouth).
Induction: 60 mg/kg IV every 8 hours for 2-3 weeks, then maintenance: 90-120 mg/kg IV once daily. Administer as a 2-hour infusion via central line.
None Documented
None Documented
Terminal elimination half-life: 2.5-3.3 hours in adults with normal renal function; up to 20 hours in anuria/end-stage renal disease.
Terminal elimination half-life is approximately 3-5 hours in patients with normal renal function; can extend to 48-120 hours in severe renal impairment (CrCl <20 mL/min), requiring dose adjustment and therapeutic drug monitoring.
Primarily renal excretion via glomerular filtration and tubular secretion: 62-91% of dose excreted unchanged in urine within 24 hours; minor biliary/fecal elimination (<2%).
Primarily renal excretion (>80% as unchanged drug) via glomerular filtration and tubular secretion; minimal biliary/fecal elimination (<5%).
Category A/B
Category C
Antiviral
Antiviral