Famvir 250 mg Tablets

Brand name

The trade name of the drug is Famvir. This is the registered name under which the drug is known in medical practice and is available in pharmacies.

International Nonproprietary Name (INN)

The international nonproprietary name is famciclovir. It denotes the active active ingredient and is used in pharmacology internationally.

Form of release

Famvir is available as film-coated tablets with dosages of 125 mg, 250 mg and 500 mg. Tablets have white color, round or oval shape (depending on the dosage) and are packed in blisters of 7, 10 or 21 pieces. This form provides accurate dosing and convenience of use for patients of all age groups, where the drug is authorized for use.

Composition

Active substance

The main active ingredient is famciclovir. One tablet contains 125 mg, 250 mg or 500 mg of famciclovir, depending on the dosage.

Auxiliary ingredients

The tablets include substances such as lactose monohydrate, microcrystalline cellulose, croscarmellose sodium, magnesium stearate, and a coating of hypromellose, titanium dioxide, and polyethylene glycol. These components ensure stability, solubility and convenience of the drug.

Pharmacologic Properties

Pharmacodynamics

Famziclovir, the active substance of Famvir, is a prodrug, which in the body is converted into penciclovir - a potent inhibitor of viral DNA polymerase. After oral administration, famciclovir is rapidly metabolized in the liver and intestinal mucosa to penciclovir, which penetrates into infected cells. Within cells, penciclovir is phosphorylated by viral thymidine kinase to the active form, penciclovir triphosphate. This form competitively blocks DNA polymerase of herpes viruses, preventing viral DNA elongation and, consequently, virus replication.

The drug is highly selective to viral enzymes, minimally affecting human cellular DNA polymerases, which reduces its toxicity. Famvir is active against herpes simplex virus types 1 and 2 (HPV-1, HPV-2), varicella-zoster virus (VZV) and to a lesser extent against Epstein-Barr virus and cytomegalovirus. The therapeutic effect is manifested by shortening the duration of rashes, reducing pain and accelerating the healing of lesions. Maximum efficacy is achieved when treatment is started in the first 24-48 hours after the onset of symptoms.

Pharmacokinetics

Absorption

Famziclovir is rapidly absorbed from the gastrointestinal tract after oral administration. The maximum concentration of penciclovir in plasma is reached in 0.5-1 hour, and bioavailability is about 77%. Food intake slows down the rate of absorption, but does not affect the overall degree of absorption, which allows taking the drug regardless of food.

Distribution

Penciclovir weakly binds to plasma proteins (less than 20%). The volume of distribution is about 1.1 L/kg, indicating penetration into tissues, including skin, mucous membranes and nervous system. The drug concentrates in infected cells, where its active form accumulates for 10-20 hours, providing prolonged action.

Metabolism

Famciclovir is metabolized in the liver and intestinal wall with the participation of aldehyde oxidase enzymes to penciclovir. About 60-65% of the administered dose is converted to the active form, the rest is excreted as intermediate metabolites (e.g. 6-deoxypenciclovir), which have no significant pharmacological activity.

Excretion

The elimination half-life of penciclovir is 2-3 hours in patients with normal renal function. The drug is excreted mainly through kidneys (about 60-70% in the form of penciclovir, the rest in the form of metabolites) by tubular filtration and tubule secretion. Complete excretion takes about 24 hours, but with impaired renal function this period may increase.

Indications for Use

Famvir is indicated for the treatment of the following conditions:

• Acute shingles (herpes zoster), including postherpetic neuralgia;
• Genital herpes (HPV-2) - primary and recurrent episodes;
• Labial herpes (HPV-1) - recurrent rashes on the lips;
• Herpetic infection in immunodeficient patients (e.g., HIV);
• Ophthalmic herpes (eye lesions caused by HPV).

The drug is effective in reducing the duration of symptoms and preventing recurrences.

Contraindications

The use of Famvir is prohibited in:

• Hypersensitivity to famciclovir, penciclovir or auxiliary components;
• Severe renal insufficiency (creatinine clearance less than 10 ml/min) without dose adjustment;
• Children under 12 years of age (due to insufficient data);
• Hereditary lactose intolerance or lactase deficiency;
• Pregnancy and lactation without strict indications.

Caution is used in severe hepatic insufficiency and immunodeficiency states.

Method of Administration and Dosage

How to take

Famvir tablets are taken orally, drinking water (100-150 ml), regardless of meals. Tablets are not chewed and crushed to preserve the stability of the active substance. For maximum efficacy, treatment should be started as soon as possible after the onset of symptoms.

Dosages for adults and children

Adults

For shingles: 500 mg 3 times daily for 7 days or 750 mg once daily for 7 days. For genital herpes: primary episode - 250 mg 3 times daily for 5 days; relapse - 125 mg 2 times daily for 5 days or 1000 mg once daily. For labial herpes: 1500 mg once or 750 mg twice daily for 1 day.

Children over 12 years of age

Dosage is similar to adults, but is used only in strict indications (e.g., shingles).

Dose adjustment for certain conditions

In renal insufficiency: creatinine clearance 30-59 ml/min - 250 mg 2 times a day (for shingles); 10-29 ml/min - 125 mg once a day. In hepatic insufficiency correction is not required, but monitoring of the condition is necessary.

Side Effects

Possible adverse reactions include:

• Nervous system: headache, dizziness, drowsiness;
• Gastrointestinal tract: nausea, diarrhea, abdominal pain;
• Skin: rash, itching, photosensitization;
• General: fatigue, fever;
• Allergic reactions: urticaria, rarely - angioedema;
• Other: increase in liver enzymes, confusion.

The side effects are usually mild and pass independently.

Overdose

Symptoms of overdose

Doses above 3000 mg may cause nausea, dizziness, confusion, and rarely acute renal failure.

First aid measures

Stop taking, call a doctor. Gastric lavage (if it has been less than an hour), give activated charcoal. If necessary, hemodialysis.

Drug Interactions

Influence on the effect of other drugs

Famvir has no significant effect on the metabolism of other drugs. Probenecid and cimetidine increase the concentration of penciclovir in blood due to decreased renal clearance.

Compatibility with alcohol and food

Alcohol does not affect efficacy but may increase dizziness. Food slows absorption without reducing the therapeutic effect.

Special Precautions

Use in pregnancy and breastfeeding

Famvir is used in pregnancy only on strict indications; lactation is stopped due to penetration into milk.

Influence on driving and mechanisms

The drug may cause dizziness and drowsiness, which requires caution when driving.

Particularities of use in elderly people and children

In the elderly, the dose is adjusted in case of impaired renal function. In children under 12 years of age the drug is not used due to lack of data.