Simplovir 400 mg

Indication:

Simplovir 400 mg is indicated for the treatment of-

• Herpes Simplex Virus (HSV-1 & HSV-2) Infections:
  • Treatment of primary and recurrent genital herpes episodes.
  • Suppression (chronic prophylaxis) of frequently recurring genital or cutaneous herpes simplex infections.
  • Treatment of Herpes Simplex Encephalitis (primarily managed via Intravenous route).
  • Prophylaxis of HSV infections in immunocompromised individuals.
• Varicella-Zoster Virus (VZV) Infections:
  • Treatment of Shingles (Herpes Zoster) to arrest cutaneous progression, alleviate acute pain, and reduce post-herpetic neuralgia.
  • Treatment of Chickenpox (Varicella) in healthy adolescents, adults, or high-risk pediatric populations.
• Topical Indications:
  • 5% Cream/Ointment: Treatment of localized herpes labialis (cold sores) and localized initial/recurrent genital herpes lesions.
  • 3% Ophthalmic Ointment: Treatment of Herpes Simplex Keratitis (corneal viral infection).

”রেজিস্ট্রার চিকিৎসকের পরামর্শ অনুযায়ী ঔষধ সেবন করুন”

Dogase & Adminstration:

Adult Dosage Protocols:

Oral Formulation (Tablets / Syrup):

• Treatment of Genital/Cutaneous HSV: 200 mg taken 5 times daily (spaced every 4 hours while awake) for 5 to 10 days. For severe/immunocompromised states, increase to 400 mg 5 times daily.
• Suppression of Recurrent HSV: 400 mg twice daily or 200 mg 3 to 4 times daily.
• Herpes Zoster (Shingles) & Severe Varicella: 800 mg taken 5 times daily for 7 full days. Must be initiated within 72 hours of rash onset for optimal clinical outcomes.

Intravenous Infusion (IV) Protocol:

• Mucocutaneous HSV in Immunocompromised Patients: 5 mg/kg administered via slow IV infusion every 8 hours for 7 days.
• Severe Herpes Zoster (Shingles): 10 mg/kg via slow IV infusion every 8 hours for 7 to 10 days.
• Herpes Simplex Encephalitis: 10 mg/kg via slow IV infusion every 8 hours for 14 to 21 days.

Topical Formulation (Cream / Ointment):

• Apply a thin layer of 5% Cream/Ointment directly to the lesions 5 times daily (every 3 to 4 hours) for 4 to 10 days. Do not apply inside mucous membranes (mouth or eyes).

Ophthalmic Formulation (Eye Ointment):

• Apply a 1 cm ribbon of 3% Ophthalmic Ointment inside the lower conjunctival sac 5 times daily until healing is complete, then continue 3 times daily for at least 3 additional days.

Pediatric Dosage Protocols:

• Neonatal HSV Infection (0 to 3 Months): 20 mg/kg administered strictly via Intravenous Infusion every 8 hours for 14 to 21 days. Oral forms are completely inappropriate here.
•  Oral Dosage (Children over 2 Years):
• HSV Infection: Children less 2 years should receive adult doses (200 mg 5 times daily). Children < 2 years should receive half the adult dose (100 mg 5 times daily).
• Varicella (Chickenpox): 20 mg/kg/dose orally 4 times daily (maximum of 800 mg per dose) for 5 days.
• Intravenous Dosage (Children 3 Months to 12 Years): Dosed based on body surface area rather than weight: 250 mg/m^2 or 500 mg/m^2 every 8 hours depending on viral severity.

Administration Guidelines:

• • IV Administration Warning: Must be infused via slow intravenous infusion over a minimum of 60 minutes. Rapid IV bolus or push is strictly prohibited as it precipitates Acyclovir crystals within the renal tubules, inducing acute kidney injury.
  • Hydration: Maintain high fluid intake and excellent patient hydration during systemic therapy to wash renal pathways.

”রেজিস্ট্রার চিকিৎসকের পরামর্শ অনুযায়ী ঔষধ সেবন করুন”

Pharmacology:

• Mechanism of Action (MOA): Acyclovir functions as a selective prodrug targeting viral-infected host cells. Its cellular activation cascade proceeds via a highly specific, three-step phosphorylation process:
  • Monophosphorylation: Upon entering an infected cell, Acyclovir is converted into Acyclovir monophosphate exclusively by the viral enzyme Thymidine Kinase (TK). Because human cellular thymidine kinase does not efficiently utilize Acyclovir as a substrate, this conversion is restricted almost entirely to infected cells, ensuring exceptional safety.
  • Diphosphorylation & Triphosphorylation: Host cell cellular kinases subsequently convert the monophosphate form into the highly active metabolite, Acyclovir Triphosphate (ACV-TP).
  • Viral DNA Polymerase Inhibition: ACV-TP acts as a competitive substrate for viral DNA polymerase. It incorporates directly into the growing viral DNA chain, functioning as an absolute obligate chain terminator. Because it lacks a $3’text{-hydroxyl}$ group, no further nucleosides can be attached, permanently halting viral DNA replication.
• Pharmacodynamics: The antiviral potency of Acyclovir decreases in the following order: Herpes Simplex Virus Type 1 (HSV-1), Herpes Simplex Virus Type 2 (HSV-2), Varicella-Zoster Virus (VZV), and Epstein-Barr Virus (EBV). It exhibits minimal to no toxicity towards uninfected healthy human cells.
• Pharmacokinetics:
  • Absorption: Slowly and only partially absorbed from the human gastrointestinal tract following oral administration, yielding an oral bioavailability of approximately 15% to 30%. Absorption is not significantly affected by food intake. Topical forms produce minimal systemic concentration.
  • Distribution: Widely distributed into bodily tissues and fluids, including the brain, kidney, saliva, lungs, and vaginal secretions. Cerebrospinal fluid (CSF) concentrations reach approximately 50% of corresponding plasma levels. It crosses the placenta and enters breast milk. Protein binding is low (9% to 33%).
  • Metabolism & Elimination: Minimally metabolized in the liver to its minor inactive metabolite, 9-carboxymethoxymethylguanine. It is eliminated predominantly via the kidneys through glomerular filtration and active tubular secretion as unchanged active drug (~60% to 91%). The elimination half-life is approximately 2.5 to 3 hours in adults with normal renal function, but extends up to 20 hours in patients with end-stage renal failure, and is approximately 4 hours in neonates.

Side Effects:

• Oral Side Effects: Nausea, vomiting, diarrhea, abdominal pain, headache, dizziness, skin rashes, and photosensitivity.
• Intravenous Side Effects: Transient elevations of blood urea nitrogen (BUN) and creatinine, localized phlebitis or inflammation at the injection site, and rare neurotoxicity (confusion, tremors, hallucinations, encephalopathy).
• Topical/Ophthalmic Side Effects: Mild transient stinging, burning, pruritus, or superficial punctate keratopathy (for eye ointment).

Drug Interaction:

• Nephrotoxic Agents: Co-administration with other nephrotoxic drugs (e.g., Aminoglycosides, Cisplatin, Cyclosporine, NSAIDs) amplifies the risk of severe renal impairment.
• Probenecid & Cimetidine: These agents compete for active renal tubular secretion, increasing the Area Under the Curve (AUC) of Acyclovir, thereby elevating blood concentrations and systemic toxicity risks.
• Mycophenolate Mofetil: Alters plasma concentrations of both drugs due to competitive renal elimination pathways.

Pregnancy & Lactation:

• Pregnancy: Category B. Extensive epidemiological registry data indicate that Acyclovir does not increase the baseline incidence of congenital birth defects when used during pregnancy. It is indicated for treating severe maternal HSV/VZV infections and preventing vertical transmission to the newborn.
• Lactation: Acyclovir passes into breast milk, achieving concentrations up to 4 times higher than maternal plasma levels. However, the calculated infant dose via breast milk is minimal (~1% of therapeutic infant doses). Use with caution, ensuring topical applications are not located on the breast tissue.

Over Dosage:

Oral overdoses are generally non-toxic due to poor GI absorption. However, massive intravenous overdoses or unadjusted doses in renal failure can cause high serum concentrations, leading to crystallization in renal tubules, acute renal failure, and severe neurotoxic responses (seizures, coma). Treatment includes stopping the drug immediately, ensuring aggressive hydration to promote diuresis, and utilizing hemodialysis if necessary to clear the drug from circulation.

Therapeutic Class:

Antiviral Agent / Nucleoside Analogue

Storage Conditions:

Store below at 30°C  temperature in a dry place. Away from light and out of reach of children. Do not use the medication after its expiration date.