ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE
Clinical safety rating
safeNo significant drug interactions Can cause hypernatremia and fluid overload.
Acyclovir is a synthetic purine nucleoside analog with inhibitory activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), and varicella-zoster virus (VZV). After intracellular conversion to acyclovir triphosphate, it inhibits viral DNA polymerase, leading to chain termination and viral DNA replication inhibition.
| Metabolism | Acyclovir is partially metabolized by aldehyde oxidase and alcohol dehydrogenase to 9-carboxymethoxymethylguanine and other minor metabolites. The majority (62-90%) is excreted unchanged in urine via glomerular filtration and tubular secretion. |
| Excretion | Primarily renal excretion via glomerular filtration and tubular secretion; approximately 62-91% of an administered dose is recovered unchanged in urine. Fecal excretion is minimal (<2%). |
| Half-life | Terminal elimination half-life in adults with normal renal function is 2.5-3.3 hours. In anuric patients, half-life extends to approximately 19.5 hours, necessitating dosage adjustment in renal impairment. |
| Protein binding | 9-33% bound to plasma proteins; binding is concentration-independent and predominantly to albumin. |
| Volume of Distribution | Approximately 0.7 L/kg, indicating distribution into total body water. Penetrates well into tissues, including cerebrospinal fluid (CSF concentrations ~50% of plasma). |
| Bioavailability | Intravenous administration yields 100% bioavailability. Oral bioavailability is 15-30% (not applicable to IV formulation). |
| Onset of Action | Intravenous administration: Onset of antiviral effect occurs within hours, with peak plasma concentrations achieved by end of infusion. Clinical improvement (e.g., reduced viral shedding, lesion healing) is typically observed within 24-48 hours. |
| Duration of Action | Antiviral activity persists as long as plasma concentrations exceed the IC50 for HSV/VZV (typically 0.1-1.6 μg/mL). Clinically, a single IV dose provides antiviral coverage for approximately 8 hours due to rapid renal clearance. Dosing every 8 hours maintains therapeutic levels. |
| Molecular Weight | 225.2 |
5 mg/kg IV every 8 hours (or 10 mg/kg IV every 8 hours for varicella-zoster or herpes simplex encephalitis) infused over 1 hour.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl >50 mL/min: no adjustment; CrCl 25-50 mL/min: 5-10 mg/kg every 12 hours; CrCl 10-25 mL/min: 5-10 mg/kg every 24 hours; CrCl <10 mL/min: 2.5-5 mg/kg every 24 hours; hemodialysis: give dose after dialysis. |
| Liver impairment | No dose adjustment required for hepatic impairment; acyclovir is minimally metabolized by the liver. |
| Pediatric use | Neonates (0-3 months): 10 mg/kg IV every 8 hours for HSV; Infants and children (3 months-12 years): 10 mg/kg IV every 8 hours for HSV, 20 mg/kg IV every 8 hours for VZV; maximum dose 500 mg/m² per dose. |
| Geriatric use | Elderly patients may have reduced renal function; adjust dose based on CrCl and monitor for neurotoxicity (e.g., confusion, hallucinations). |
| 1st trimester | Acyclovir crosses the placenta. Limited human data; animal studies show no evidence of teratogenicity. Use only if clearly needed. |
| 2nd trimester | Considered safe; preferred antiviral for HSV/VZV in pregnancy. Use at lowest effective dose. |
| 3rd trimester | Well-tolerated; increased clearance in late pregnancy may require dose adjustment. |
Clinical note
No significant drug interactions Can cause hypernatremia and fluid overload.
| FDA category | Animal |
| Placental transfer | Crosses the placenta with cord blood levels 60-100% of maternal serum levels. |
| Breastfeeding | Acyclovir is excreted into breast milk in small amounts; peak concentration ~0.6-4.1% of maternal dose. No adverse effects reported in infants. Compatible with breastfeeding. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data: no increased risk of major birth defects or miscarriage. Risk cannot be ruled out; use only if clearly needed. |
| Fetal Monitoring | Monitor renal function (serum creatinine, BUN) and urine output, especially in preeclampsia or renal impairment. Monitor for CNS effects (e.g., confusion, hallucinations). Fetal monitoring per standard obstetrical care. |
| Fertility Effects | No evidence of impaired fertility in animal studies at clinically relevant doses. No human data on fertility effects. Not expected to significantly impact fertility. |
■ FDA Black Box Warning
None.
| Common Effects | fluid replacement |
| Serious Effects |
Hypersensitivity to acyclovir or valacyclovir
| Precautions | Renal impairment: Dose adjustment required; monitor renal function., Neurotoxicity: May cause agitation, hallucinations, confusion, seizures (especially in elderly or renally impaired)., Crystalluria: Risk increased with rapid infusion or dehydration; ensure adequate hydration., Hemolytic uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP): Rare but serious, reported in immunocompromised patients., Pregnancy: Use only if clearly needed (Category B). |
| Food/Dietary | No specific food interactions. Adequate fluid intake is recommended to prevent renal toxicity. Avoid concurrent use of nephrotoxic substances (e.g., certain NSAIDs, aminoglycosides) without medical supervision. |
| Clinical Pearls | Acyclovir in sodium chloride 0.9% preservative-free is for IV administration only; do not administer IM or SC. Infuse over at least 1 hour to prevent renal tubular damage. Monitor renal function and adjust dose in renal impairment (CrCl <50 mL/min). Ensure adequate hydration (e.g., 500 mL IV fluids per gram acyclovir) to reduce risk of crystalluria. In obese patients, use ideal body weight for dosing. Phlebitis at infusion site is common; rotate sites. |
| Patient Advice | This medication is given intravenously (into a vein) to treat viral infections. · Drink plenty of fluids before and during treatment to prevent kidney problems. · Report any pain, redness, or swelling at the injection site, or any lower back pain. · Tell your healthcare provider if you have kidney disease or are taking other medications that can affect the kidneys. · This drug does not cure herpes infections but helps reduce symptoms and recurrence. |
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