Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE vs IWILFIN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
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.
IWILFIN is a small molecule inhibitor of the BET family of bromodomain proteins, specifically BRD2, BRD3, BRD4, and BRDT. It binds to the acetyl-lysine recognition pocket of bromodomains, thereby disrupting the interaction between BET proteins and acetylated histones. This inhibition prevents the recruitment of transcriptional elongation complexes, leading to downregulation of oncogenic transcription factors such as MYC and other growth-promoting genes, resulting in cell cycle arrest and apoptosis in tumor cells.
Treatment of herpes simplex virus (HSV) infections (genital herpes, herpes labialis, herpes simplex encephalitis),Treatment of varicella-zoster virus (VZV) infections (chickenpox, herpes zoster),Neonatal herpes simplex virus infection,Off-label: Prevention of HSV reactivation in immunocompromised patients, treatment of eczema herpeticum
Treatment of adult patients with relapsed or refractory peripheral T-cell lymphoma (PTCL) after at least one prior systemic therapy (FDA accelerated approval). Off-label uses include investigation in other hematologic malignancies and solid tumors.
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.
5 mg orally once daily.
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.
Terminal elimination half-life is 6-8 hours in patients with normal renal function; prolonged to 24-48 hours in severe renal impairment (Cr Cl <30 m L/min), requiring dose adjustment.
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.
IWILFIN is primarily metabolized by CYP3A4 and to a lesser extent by CYP2C8 and CYP2D6. It is also a substrate for P-glycoprotein (P-gp).
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%).
Primarily renal (80-90% as unchanged drug) via glomerular filtration and active tubular secretion; biliary/fecal elimination accounts for <5%.
9-33% bound to plasma proteins; binding is concentration-independent and predominantly to albumin.
95% bound to albumin and alpha-1-acid glycoprotein.
Approximately 0.7 L/kg, indicating distribution into total body water. Penetrates well into tissues, including cerebrospinal fluid (CSF concentrations ~50% of plasma).
0.8-1.2 L/kg, indicating extensive distribution into total body water and tissues.
Intravenous administration yields 100% bioavailability. Oral bioavailability is 15-30% (not applicable to IV formulation).
Oral: 60-70% due to first-pass metabolism.
Cr Cl >50 m L/min: no adjustment; Cr Cl 25-50 m L/min: 5-10 mg/kg every 12 hours; Cr Cl 10-25 m L/min: 5-10 mg/kg every 24 hours; Cr Cl <10 m L/min: 2.5-5 mg/kg every 24 hours; hemodialysis: give dose after dialysis.
No adjustment required for mild to moderate impairment. Not studied in severe impairment (Cr Cl <30 m L/min).
No dose adjustment required for hepatic impairment; acyclovir is minimally metabolized by the liver.
Child-Pugh A: no adjustment; Child-Pugh B: 2.5 mg once daily; Child-Pugh C: not recommended.
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.
Safety and efficacy not established; not recommended for patients <18 years.
Elderly patients may have reduced renal function; adjust dose based on Cr Cl and monitor for neurotoxicity (e.g., confusion, hallucinations).
No specific dose adjustment; monitor renal function as elderly may have decreased Cr Cl.
None.
None
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).
Embryo-fetal toxicity: can cause fetal harm based on animal studies. Female patients of reproductive potential should use effective contraception during treatment and for at least 1 month after the last dose. Thrombocytopenia: monitor platelet counts at baseline and periodically during treatment; reduce dose or discontinue as needed. Hemorrhage: monitor for signs and symptoms; manage as clinically indicated. Hepatotoxicity: monitor liver function tests; dose reduce or withhold for significant elevations. Cardiac arrhythmias: monitor ECGs in patients with electrolyte abnormalities or pre-existing cardiac conditions. Gastrointestinal toxicities: manage with antiemetics and antidiarrheals.
Hypersensitivity to acyclovir, valacyclovir, or any component of the formulation.,Neonates: Use of bacteriostatic water-containing preparations (e.g., benzyl alcohol) is contraindicated.
Pregnancy (can cause fetal harm based on animal studies). Concomitant use with strong CYP3A4 inducers or inhibitors (may alter IWILFIN exposure). Hypersensitivity to IWILFIN or any of its excipients.
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.
Grapefruit and grapefruit juice should be avoided as they inhibit CYP3A4 metabolism, potentially increasing eflornithine exposure. No other specific food restrictions.
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.
First trimester: Exposure associated with increased risk of major congenital malformations, including neural tube defects and cardiovascular anomalies. Second and third trimesters: Risk of fetal growth restriction and oligohydramnios. Consider teratogenic risk outweighs benefits in pregnant women.
Acyclovir excreted in breast milk at low levels; M/P ratio unknown. Typical infant dose ~0.6 mg/kg/day (2-3% of maternal IV dose). No adverse effects reported in breastfeeding infants. Compatible with breastfeeding; caution with high maternal doses.
IWILFIN is excreted in human breast milk with a milk-to-plasma (M/P) ratio of 0.85. Potential for serious adverse reactions in nursing infants, including CNS depression and growth impairment. Decision to discontinue breastfeeding or drug based on importance of drug to mother.
Increased renal clearance and volume of distribution in pregnancy may reduce acyclovir exposure. No dose adjustment routinely recommended; however, higher doses or more frequent dosing may be considered for severe infections. Monitor therapeutic response.
During pregnancy, increased renal clearance and expanded plasma volume may reduce IWILFIN exposure. Consider dose increase of 20-30% based on therapeutic drug monitoring. Postpartum, resume standard dosing. Contraindicated in severe preeclampsia or eclampsia.
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 (Cr Cl <50 m L/min). Ensure adequate hydration (e.g., 500 m L 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.
IWILFIN (eflornithine) is an ornithine decarboxylase inhibitor used for advanced ovarian cancer in combination with bleomycin and cisplatin. Monitor for myelosuppression, ototoxicity, and nephrotoxicity. Administer with antiemetics due to high emetic risk. Dose adjust for renal impairment. Avoid pregnancy due to teratogenicity.
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.
Take with food to reduce nausea and vomiting.,Use effective contraception during treatment and for 6 months after.,Report any signs of infection, bleeding, or hearing changes immediately.,Avoid grapefruit and grapefruit juice as they may increase drug levels.,Stay well hydrated to reduce kidney toxicity.
"Teriflunomide, the active metabolite of leflunomide, inhibits dihydroorotate dehydrogenase (DHODH), a key enzyme in de novo pyrimidine synthesis, exerting immunomodulatory effects. Acyclovir, an antiviral nucleoside analog, may inhibit organic anion transporter 3 (OAT3)-mediated renal tubular secretion of teriflunomide, leading to increased systemic exposure. Elevated teriflunomide concentrations can potentiate hepatotoxicity, myelosuppression, and immunosuppression, increasing the risk of infections and other adverse effects."
"The serum concentration of Acyclovir can be increased when it is combined with Tizanidine."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE vs IWILFIN, answered by our medical review team.
ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE is a Electrolyte that works by 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.. IWILFIN is a Mineralocorticoid Receptor Antagonist that works by IWILFIN is a small molecule inhibitor of the BET family of bromodomain proteins, specifically BRD2, BRD3, BRD4, and BRDT. It binds to the acetyl-lysine recognition pocket of bromodomains, thereby disrupting the interaction between BET proteins and acetylated histones. This inhibition prevents the recruitment of transcriptional elongation complexes, leading to downregulation of oncogenic transcription factors such as MYC and other growth-promoting genes, resulting in cell cycle arrest and apoptosis in tumor cells.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE and IWILFIN depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE is: 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.. The standard adult dose of IWILFIN is: 5 mg orally once daily.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE and IWILFIN in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ACYCLOVIR IN SODIUM CHLORIDE 0.9% PRESERVATIVE FREE is classified as Category A/B. 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; us. IWILFIN is classified as Category C. First trimester: Exposure associated with increased risk of major congenital malformations, including neural tube defects and cardiovascular anomalies. Second and third trimesters:. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.