Medication Guide for Famvir

Active Ingredient

Famvir contains famciclovir as its active ingredient. Famciclovir is a synthetic nucleoside analog antiviral agent. It is rapidly converted to its active form, penciclovir, in the body.

Mechanism of Action

Famciclovir is converted into penciclovir by enzymatic activity. Penciclovir inhibits viral DNA polymerase by competing with deoxyguanosine triphosphate. This mechanism terminates viral DNA chain elongation.

Formulations Available

Famvir is available in oral tablet form. The available strengths include 125 mg, 250 mg, and 500 mg tablets. The tablets are typically white, film-coated, and oblong-shaped with dose-specific markings.

Indications for Use

Famvir is indicated for the treatment of acute herpes zoster (shingles). It is also used for the treatment and suppression of recurrent genital herpes in immunocompetent patients. Additionally, Famvir is indicated for treating recurrent herpes simplex virus infections in HIV-infected persons.

Dosage Recommendations

The typical dose for acute herpes zoster is 500 mg every eight hours for seven days. For recurrent genital herpes, the recommended dose is 125 mg twice daily for five days. For herpes simplex virus infections in HIV-infected patients, the dose is 500 mg twice daily for seven days.

Administration Guidelines

Famvir tablets should be swallowed whole with water. They can be taken with or without food. Consistent timing of doses enhances therapeutic efficacy. Avoid crushing or chewing the tablets.

Pharmacokinetics

Upon oral administration, Famvir achieves peak plasma concentrations within one hour. The bioavailability of famciclovir is approximately 77%. Famciclovir is extensively metabolized by the liver to penciclovir. The elimination half-life of penciclovir is approximately 2-3 hours in patients with normal renal function.

Storage Conditions

Famvir should be stored at room temperature, between 15°C to 30°C (59°F to 86°F). It should be kept in a tightly closed container, away from moisture and light. Do not store in the bathroom or near a sink.

Potential Drug Interactions

Co-administration with probenecid may increase the plasma concentrations of penciclovir. Concurrent use of allopurinol may also increase the risk of famciclovir toxicity. Consult a healthcare provider before combining Famvir with other medications.

Special Populations Considerations

Renal impairment significantly affects the pharmacokinetics of Famvir, necessitating dosage adjustments. In elderly patients, dose modification may be required due to age-related decreases in renal function. Safety and efficacy have not been established in pediatric patients under 18 years of age.

Side Effects Profile

Common side effects include headache, nausea, and diarrhea. Less frequently, patients may experience fatigue, vomiting, and abdominal pain. Rare but severe adverse effects include jaundice, severe skin reactions, and renal impairment.

Overdose Management

In case of overdose, gastric lavage may be considered if the person is conscious and alert. Supportive care and symptomatic treatment should be instituted. Hemodialysis can effectively reduce plasma levels of penciclovir in cases of severe toxicity.

Monitoring Parameters

Renal function should be monitored before and during treatment in patients with preexisting kidney conditions. Liver function tests may be indicated for patients with hepatic impairment. Viral load assessments can be useful in evaluating therapeutic efficacy.

Manufacturer Information

Famvir is developed and manufactured by Novartis Pharmaceuticals Corporation. The company provides comprehensive information regarding indications, dosages, and additional product-specific details upon request.

Patents and Exclusivity

Famvir was initially granted FDA approval in 1994. Patents and exclusivity rights have since expired, allowing for the production of generic versions. The original brand, however, maintains proprietary manufacturing techniques and formulations.

Special Storage Instructions

Famvir should not be stored in the freezer. Keep the medication out of reach of children and pets. Do not use the medication past its expiration date.

Visual Identification

Each tablet is embossed with identifiers specific to the dosage strength. Tablets are usually white or off-white and film-coated to improve palatability. Visual inspection prior to administration ensures correct dosage strength.