Zovirax 800 mg Tablets

Brand name

The trade name of the drug is Zovirax. This is the registered name under which the drug is known in medical practice and is available in the pharmacy network.

International Nonproprietary Name (INN)

The international nonproprietary name is acyclovir. It denotes the active active ingredient and is used in pharmacology at the international level.

Form of release

Zovirax is available in several forms: 200 mg, 400 mg and 800 mg tablets packed in blisters of 5, 10 or 25 pieces; cream 5% in tubes of 2 g, 5 g or 10 g; eye ointment 3% in tubes of 4.5 g; powder for preparing a solution for infusion of 250 mg in bottles. Tablets have white color, cream and ointment - white homogeneous consistency, and the powder is intended for dilution in medical conditions.

Composition

Active substance

The main active component is acyclovir. One tablet contains 200 mg, 400 mg or 800 mg acyclovir; 1 g cream - 50 mg; 1 g eye ointment - 30 mg; one vial of powder - 250 mg.

Auxiliary Components

Tablets include lactose monohydrate, microcrystalline cellulose, sodium starch glycolate, povidone, magnesium stearate. The cream contains propylene glycol, cetyl alcohol, white petroleum jelly, poloxamer 407, purified water. Eye ointment - white petroleum jelly. Powder for infusion - sodium hydroxide and water for injection (after dilution).

Pharmacologic Properties

Pharmacodynamics

Acyclovir, the active substance of Zovirax, is a synthetic analog of purine nucleoside with pronounced antiviral action. After penetration into infected cells, acyclovir is phosphorylated by viral thymidine kinase to acyclovir monophosphate and then by cellular enzymes to acyclovir triphosphate. This active form competitively inhibits viral DNA polymerase, preventing the synthesis of new viral DNA, which stops viral replication. The drug is highly selective to viral enzymes, minimally affecting human DNA, which ensures its safety.

Zovirax is active against herpes simplex virus types 1 and 2 (HPV-1, HPV-2), varicella-zoster virus (VZV), as well as partially against Epstein-Barr virus and cytomegalovirus. When applied topically (cream, ointment), it quickly relieves itching, pain and inflammation, accelerating the healing of rashes. When administered systemically (tablets, infusions), the drug reduces the viral load and prevents the spread of infection. The effect is noticeable after 1-3 days with topical treatment and after 3-7 days with systemic therapy.

Pharmacokinetics

Aciclovir absorption

Acyclovir when taken orally is partially absorbed from the gastrointestinal tract, with a bioavailability of 15-30%. Maximum concentration in plasma is reached in 1.5-2 hours. When administered intravenously, bioavailability is 100%, and peak concentration is observed immediately after infusion. When applied topically (cream, ointment), systemic absorption is minimal (less than 0.5%). Food intake does not affect absorption.

Distribution

Acyclovir is weakly bound to blood plasma proteins (9-33%). The volume of distribution is about 0.7 l/kg, which ensures penetration into the skin, mucous membranes, lungs, kidneys and cerebrospinal fluid. The drug passes through the blood-brain barrier and placental barrier, and is also excreted in breast milk.

Metabolism

Acyclovir is minimally metabolized in the liver (10-15%). The main metabolite, 9-(carboxymethoxymethoxymethyl)guanine (CMMG), is formed with the participation of alcohol dehydrogenase and aldehyde dehydrogenase enzymes and has no significant activity.

Excretion

Half-life of acyclovir is 2.5-3 hours during oral and intravenous administration. The drug is excreted mainly through kidneys (about 85-90% in unchanged form) by tubular filtration and tubule secretion. Complete excretion takes about 24 hours, but in renal insufficiency this period increases.

Indications for Use

Zovirax is prescribed for the treatment of the following conditions:

• Infections of the skin and mucous membranes caused by HPV-1 and HPV-2 (labial and genital herpes);
• Shingles (herpes zoster), including the acute phase;
• Prevention of herpes recurrences in normal and immunocompromised patients;
• Herpetic keratitis and conjunctivitis (eye ointment);
• Severe herpetic infections in immunocompromised patients (infusions).

The drug is effective in controlling symptoms and preventing complications.

Contraindications

The use of Zovirax is prohibited in:

• Hypersensitivity to acyclovir, valacyclovir or auxiliary components;
• Severe renal insufficiency (creatinine clearance less than 10 ml/min) without dose adjustment;
• Children under 2 years of age (for tablets) or under 3 months of age (for infusions);
• Dehydration or severe hypovolemia (for infusions).

With caution prescribe in neurological disorders, hepatic insufficiency, pregnancy.

Method of Administration and Dosage

How to take

Zovirax tablets are taken orally, drinking water (100-150 ml), regardless of meals. Cream is applied in a thin layer on the affected areas 5 times a day every 4 hours. Eye ointment is placed in the conjunctival sac 5 times a day. Infusion solution is prepared and administered intravenously slowly (1 hour) by medical personnel.

Dosages for adults and children

Adults

Tablets: for herpes of the skin and mucous membranes - 200 mg 5 times a day for 5 days; for shingles - 800 mg 5 times a day for 7 days; prophylaxis - 200 mg 4 times a day. Cream: 5 times a day for 4-10 days. Infusions: 5-10 mg/kg every 8 hours for 5-7 days.

Children over 2 years of age

Tablets: 20 mg/kg (maximum 800 mg) 4-5 times daily for 5 days. Cream: as in adults. Infusions: 250 mg/m² every 8 hours for children older than 3 months.

Dose adjustment for certain conditions

In renal insufficiency: creatinine clearance 25-50 ml/min - 800 mg 3 times a day; 10-25 ml/min - 800 mg 2 times a day. In hepatic insufficiency correction is usually not required.

Side Effects

Possible adverse reactions include:

• Gastrointestinal tract: nausea, vomiting, diarrhea, abdominal pain;
• Nervous system: headache, dizziness, confusion;
• Skin: rash, itching, photosensitization;
• Hematopoietic system: leukopenia, thrombocytopenia (rare);
• Allergic reactions: urticaria, angioedema;
• Other: creatinine increase, fatigue.

The side effects are more often mild and reversible.

Overdose

Symptoms of overdose

Doses above 20 g (tablets) or 100 mg/kg (infusions) may cause nausea, convulsions, renal failure, and confusion.

First aid measures

Stop administration, call a doctor. Gastric lavage (for tablets), give activated charcoal. Hemodialysis is required for infusions.

Drug Interactions

Influence on the effect of other drugs

Zovirax has no significant effect on the metabolism of other drugs. Probenecid and cimetidine slow down the excretion of acyclovir, increasing its concentration. Nephrotoxic drugs increase the risk of renal impairment.

Compatibility with alcohol and food

Alcohol does not affect efficacy but may increase dizziness. Food does not alter absorption.

Special Precautions

Use in pregnancy and breastfeeding

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

Influence on driving and mechanisms

The drug may cause dizziness, 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 2 years of age tablets are not used; infusions - from 3 months.