Zovirax: Acyclovir Medicine Used to Treat Herpes Virus Infections
Zovirax is an antiviral drug that slows the growth and spread of the herpes virus in the body.
What is Zovirax used for?
The medicine is used to treat:
- herpes simplex of the skin, mucous membranes;
- genital herpes infection;
- shingles (Herpes zoster);
- chickenpox (on the first day after the onset of a typical rash);
- severe immunodeficiency (including in the period after transplantation, with the use of immunosuppressive drugs, HIV-infected, against the background of chemotherapy).
How does it work?
The active ingredient of the drug is acyclovir, an antiviral agent. It is an analogue (synthetic) of a purine nucleoside with inhibitory activity against the human herpes virus, incl. herpes simplex virus (Herpes simplex) type I and II, herpes zoster virus and chickenpox (Varicella zoster), Epstein-Barr virus, cytomegalovirus.
Acyclovir is most active (as the activity decreases): against herpes simplex virus type I, herpes simplex virus type II, Varicella zoster virus (chickenpox, herpes zoster), Epstein-Barr virus, cytomegalovirus. The inhibitory activity against the above viruses is highly selective (highly selective). In a normal (uninfected) cell, the thymidine kinase enzyme does not use acyclovir as a substrate, due to which the toxic effect on the cells of the host organism is minimal. Thymidine kinase converts acyclovir to acyclovir monophosphate – a nucleoside analogue, which is sequentially converted by cell enzymes to diphosphate and triphosphate. Triphosphate integrates into viral DNA, interacts with viral DNA polymerase, resulting in the termination of the synthesis of the viral DNA chain.
How to take Zovirax?
The drug is taken orally.
The standard dose for infection with Herpes simplex type I and II is 200 mg every 4 hours during the day and 8-hour break at night (5 times a day) for five days.
The standard dose as part of complex therapy for severe immunodeficiency is 400 mg five times a day.
The standard dose to prevent recurrence of infection caused by Herpes simplex is 200 mg every 6 hours (four times a day), the maximum dose is 400 mg five times a day.
The standard dose for an infection caused by Varicella zoster is 800 mg every 4 hours during the day and an 8-hour break at night (five times a day) for 7-10 days.
Children over 2 years old – 20 mg / kg 4 times a day for five days.
The standard dose for an infection caused by Herpes zoster is 800 mg 4 times a day (every 6 hours during the day) for 5 days.
How quickly do Zovirax pills work?
It may take up to 2 hours to reach peak plasma concentrations after oral drug administration. It may take up to 3 days for symptom reduction; however, the medicine should be taken until the course prescribed by a doctor is completed. The drug works best when started within 48 hours of symptom onset.
Is Zovirax the same as acyclovir?
Acyclovir is a generic version of Zovirax. Therefore, these drugs wosk the same way and have the same efficiency.
Is Zovirax available over the counter?
The medicine is available over-the-counter (OTC).
Who should not use it?
Do not use the drug if you have any of the following conditions:
- hypersensitivity reactions to this medicine;
- age under three years.
With caution: pregnancy, dehydration, renal failure.
What are the side effects of Zovirax?
- Blood and lymphatic system: anemia, thrombocytopenia, lymphopenia;
- Immune system: anaphylaxis;
- Mental disorders and disorders of the nervous system: headache, dizziness, agitation, confusion, tremors, attacks, dysarthria, hallucinations, psychotic symptoms, convulsions, drowsiness, encephalopathy, coma. These neurological symptoms are generally reversible and usually occur in patients with renal failure or other risk factors;
- Respiratory system and chest organs: shortness of breath;
- Gastroenterological system: nausea, vomiting, diarrhea, abdominal pain;
- Hepatobiliary system: a reversible increase in the level of bilirubin and liver enzymes, jaundice, hepatitis;
- Skin and subcutaneous tissue: itching, rashes (including photosensitivity), angioedema, urticaria, accelerated diffuse hair loss. Since hair loss can be associated with a large number of diseases and drugs used, a clear connection with acyclovir has not been established;
- Kidneys and urinary system: increased levels of creatinine and urea in the blood, acute renal failure, pain in the kidneys. Kidney pain can be associated with renal failure and crystalluria;
- General disorders: fatigue, fever.
Can it interact with other drugs?
There is no clinically significant interaction of acyclovir with other drugs.
The medicine is mainly excreted by the kidneys by tubular secretion, therefore, any drugs with a similar mechanism of excretion can increase the concentration of acyclovir in blood plasma.
Probenecid and cimetidine lengthen the T½ of acyclovir and increase the AUC value, but due to the wide therapeutic index of acyclovir, there is no need to adjust the dose of the drug.
When used with an immunosuppressant in the treatment of patients after organ transplantation (mycophenolate mofetil) in the blood plasma, the level of acyclovir and the inactive metabolite of mycophenolate mofetil also increases, but taking into account the wide therapeutic index of acyclovir, dose adjustment is not required.
An experimental study of 5 men indicates that concomitant therapy with acyclovir increases the AUC of fully administered theophylline by about 50%. It is recommended to measure the concentration of theophylline in blood plasma when combined with acyclovir.
Can you use too much Zovirax?
You should take the medicine in doses prescribed by a doctor. If you take too much medication, you can get an overdose.
Symptoms. The medicine is only partially absorbed in the gastrointestinal tract. There were cases of inadvertent ingestion of up to 20 g of acyclovir by patients without a toxic effect. In case of an accidental repeated overdose of oral acyclovir within several days, gastroenterological (nausea, vomiting) and neurological symptoms (headache and confusion) occur.
Treatment. The patient must be examined to identify symptoms of intoxication. Since the level of the medicine in the blood is well eliminated by hemodialysis, the latter is used in case of an overdose.
Can I use this drug during pregnancy and breastfeeding?
No controlled clinical trials have been conducted regarding the safety of this drug in pregnant women. Use is possible only in cases where the expected benefit to the body for the mother outweighs the likely risk to the fetus.
The drug passes into breast milk, therefore, its use by nursing patients is not recommended.
Are there any special instructions?
The dosage regimen for patients with impaired renal function should be adjusted.
Deterioration of kidney function can be detected with dehydration, combined use with other nephrotoxic drugs, or with a history of kidney disease. Special care should be taken in patients taking large doses of acyclovir (for example, in Herpes encephalitis), especially in dehydrated patients or patients with impaired renal function.
The medicine does not affect the ability to drive vehicles and work with mechanisms.