VIREST Tablet

For the treatment of viral infections due to herpes simplex virus (type 1&2) and varicella-zoster virus (zoster & chickenpox).

DOSAGE AND ADMINISTRATION

Adults

Genital herpes infection:

Ÿ Initial therapy: Oral, 200mg 5 times a day for 10 days

Ÿ Intermittent therapy: Oral, 200mg 5 times a day for 5 days

Ÿ Chronic suppressive therapy: Oral, 400mg twice a day or 200mg 2-5 times a day.

See the package insert about dosage for patients with renal impairment.

Herpes zoster:

Oral, 800mg 5 times a day for 7-10 days

See the package insert about dosage for patients with renal impairment.

Varicella:

Oral, 20mg/kg, up to 800mg/dose, 4 times a day for 5 days.

Treatment should be initiated at the earliest sign or symptoms of chickenpox.

Herpes simplex:

Oral, 200-400mg 5 times a day for 10 days in immunocompromised patients.

Paediatrics

Children <2 years:

Dosage has not been established in children up to 2 years of age. However, no unusual toxicity or paediatric-specific problems have been observed in studies done in children using doses of up to 300mg/m2/day and 80mg/kg/day.

Children 2-12 years:

Varicella:

Oral 20mg/kg, up to 800mg/dose, 4 times a day for 5 days.

Treatment should be initiated at the earliest sign or symptom of chickenpox.

Note; The information given here is limited. For further information, consult your doctor or pharmacist.

Hypersensitivity to aciclovir or ganciclovir.

- Acute renal failure.

- Gastrointestinal disturbances (nausea or vomiting, diarrhea, abdominal pain).

- Headache.

- Increase in blood concentrations of urea and creatinine.

- Light headedness.

- Increase values for liver enzymes.

- Skin rashes.

- Encephalopathic changes (lethargy, confusion, tremors, seizures).

- Haematological changes.

Probenecid reduces excretion of aciclovir when used concurrently, resulting in increased aciclovir plasma concentration and risk of toxicity.

- Aciclovir crosses placenta. No adverse fetal effects have been reported. FDA pregnancy category C.

- Aciclovir passes into breast milk. No toxicity was observed in infants.

- Dehydration or renal function impairment - intravenous aciclovir may increase the potential for nephrotoxicity; it is recommended that aciclovir be administered in a reduced dosage to patients with impaired renal function.

- Neurological abnormalities or prior neurologic reactions to cytotoxic medications - intravenous aciclovir may increase the potential for neurologic side effects.

- Aciclovir should be used with caution to patients with renal impairment and doses should be adjusted according to creatinine clearance.

- Women with herpes genitalis may have an increased risk of developing cervical cancer; annual Pap tests may be required. Checking with physician if no improvement within a few days.

- Use of aciclovir has not been shown to prevent the transmission of herpes simplex virus to sexual partners.

Aciclovir is converted to aciclovir monophosphate, a nucleotide, by the viral thymidine kinases of herpes simplex virus (HSV) and varicella-zoster virus (VZV). Aciclovir monophosphate is converted to the diphosphate by cellular guanylate kinase and to the triphosphate by a number of cellular enzymes. Aciclovir triphosphate interferes with HSV and VZV DNA polymerase and inhibits viral DNA replication. The triphosphate can be incorporated into growing chains of DNA by viral DNA polymerase, resulting in termination of the DNA chain. Aciclovir is therefore selectively converted to the active triphosphate form by HSV and VZV-infected cells.

Aciclovir crosses the placenta and are excreted through the kidney and in breast milk. The terminal half-life is reported to be 2-3 hours for adults without renal impairment. The half-life increases in patients with renal impairment.

Aciclovir is poorly absorbed from the gastrointestinal tract. Not significantly affected by food.