Valacyclovir
Mechanism :
Valaciclovir is the L-valine ester of acyclovir. A prodrug, it is rapidly converted to acyclovir by intestinal and hepatic metabolism. Acyclovir inhibits DNA synthesis and viral replication and has antiviral activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) and varicella-zoster virus.
Indication :
- Chicken pox
- Herpes Labialis
- Genital herpes
Contraindications :
Hypersensitivity to valaciclovir, acyclovir.
Dosing :
Chickenpox:
<2 years: Safety and efficacy not established.
>2 years: 20 mg/kg PO every 8 hourly dose for 5 days; not to exceed 1 g orally q8hr.
Herpes Labialis:
<12 years: Safety and efficacy not established.
>12 years: 2 g PO twice a day for 1 day.
Genital Herpes:
Use in children >12 years of age.
1st episode:
1 g PO twice a day for 10 days.
Recurrent episode:
500 mg PO twice a day for 3 days.
Prevention of recurrence:
1 g PO once a day.
Adverse Effect :
Headache, nausea, vomiting, diarrhea, LFT abnormalities, abdominal pain, rash, photosensitivity, confusion, hallucinations and thinking disorders especially at high doses, renal failure, blood dyscrasias, thrombotic thrombocytopenic purpura, hemolytic uremic syndrome. neutropenia, nasopharyngitis.
Interaction :
Probenecid: Reduced clearance with probenecid.
Ceftriaxone, Ciclosporin and other Nephrotoxic Drugs: Increased risk of renal toxicity.
Mycophenolate: Increased risk of neutropenia with mycophenolate.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 30-50 | Dose as in normal renal function |
| 15-30 | Herpes simplex: Dose as in normal renal function Herpes zoster: 1 g every 12 hours CMV prophylaxis: 1 g every 12 hours |
| <15 | Herpes simplex: 500 mg daily Herpes zoster: 1 g every 24 hours CMV prophylaxis: 1 g every 24 hours Herpes simplex suppression: Immunocompetent – 250 mg daily Immunocompromised – 500 mg daily |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Likely dialysability. Dose as in GFR<15 mL/min |
| HD | Dialysed. Dose as in GFR<15 mL/min post dialysis |
| HDF/High flux | Dialysed. Dose as in GFR<15 mL/min post dialysis |
| CAV/VVHD | Likely dialysability. Dose as in GFR=15–30 mL/min |
Hepatic Dose :
No dose adjustment recommended.