Acyclovir: instructions, indications, contraindications
Acyclovir is a modern highly effective drug designed to combat viral infections.It helps to quickly cope with diseases caused by the herpes simplex virus( Herpes simplex), and is also prescribed for herpes zoster and chickenpox.
Active ingredient and pharmacy forms of Acyclovir
Active ingredient that destroys viruses is acyclovir-2-amino-1,9-dihydro-9- [(2-hydroxyethoxy) methyl] -6H-purine-6-OH( as sodium salt).The chemical formula of this substance is C8H11N5O3.It is an artificially synthesized analogue of deoxyguanidine( DNA nucleotide).This compound is able to directly affect the enzyme system of viruses, blocking the replication of DNA of these infectious agents of a non-cellular nature.
This product is manufactured by pharmacological companies in the form of 5% ointment for application to the skin and mucous membranes and 3% ophthalmic ointment( supplied in tubes of 5 g).It can also be purchased in the form of tablets for oral administration( in contour packs - 10 pieces of 200 or 400 mg).At what diseases is Acyclovir prescribed?
Important: for HIV infection Acyclovir is ineffective, but the drug may be administered in case of unspecified immunodeficiency to prevent recurrence of herpes.
The use of acyclovir is indicated for infectious diseases caused by the introduction of the herpes simplex virus( reference to the 2nd article from the file) .
These include:
- herpetic eczema;
- vesicular form of herpetic dermatitis;
- herpetic eye damage( keratitis);
- anogenital herpetic infection;
- viral gingivostomatitis;
- pharyngutzillite.
In addition, Acyclovir is widely used in pathologies such as shingles and chicken pox.
Methods of application of Acyclovir and recommended dosages
Acyclovir in the form of tablets for oral administration is prescribed for the treatment of viral lesions of mucous membranes and skin.
For adults and children older than 2 years, the recommended single dose is 200 mg( 1 tablet).Multiplicity of the drug - 5 times a day.It is advisable to strictly maintain the time intervals between doses - 4 hours in the daytime and 8 hours at night.
Acyclovir tablets are intended for course therapy.Usually appointed a 5-day course.
If the immunodeficiency state is diagnosed, a single dose is twice as much as 400 mg, and the frequency of reception is similar.The necessary duration of the course treatment is established by the doctor, taking into account the severity of clinical manifestations and the dynamics of the process.
If the patient's immune status is normal, but there is a need to prevent the recurrence of herpes infection, the administration of 200 mg of Acyclovir 4 times a day is indicated for preventive purposes.In the prevention of relapses between doses, it is necessary to observe 6-hour intervals.
The daily allowable dose of this drug for the treatment of herpetic diseases is 2000 mg.
When treating varicella( "chicken pox") adults should take 800 mg of Acyclovir 5 times a day.The duration of the course is from 1 to 1.5 weeks.The child's dosage is determined from the calculation of 20 mg / kg.Multiplicity of admission for children - 4 times a day, and the course continues for 5 days.
Note: if the weight of the child is from 40 kg and above, he is given the same dose of the drug as the adult.
Tablets should preferably be taken during meals or immediately after.
Important: for children under 2 years of age Acyclovir is not prescribed!
In the treatment of ophthalmic diseases of viral genesis( herpetic keratitis) 3% ointment Acyclovir is used.A small( 1 cm) strip is placed in conjunctival sacs of both eyes 5 times a day.The drug should be taken until complete recovery, continuing the course of 3 more days after complete relief of symptoms.
Note: during the course of treatment with the use of ophthalmic ointment is advisable to temporarily give up contact lenses.At a low immune status it is recommended to use forms for external topical application in parallel and to take tablets.
Mechanism of action and pharmacodynamics Acyclovir
The active substance Acyclovir blocks the multiplication of the infectious agent.The highest activity of the drug exhibits herpes viruses of type 1 and type 2.
Important: has demonstrated experimentally in clinical trials that Acyclovir is capable of stopping the reproduction of the Epstein-Barr virus and cytomegalovirus.
In herpetic dermatitis, the drug is able to prevent the appearance of new rashes, reduce the likelihood of the spread of the pathogen and the defeat of the virus of internal organs.Acyclovir significantly speeds up the drying process of the blisters on the skin and mucous membranes.It is noted that in the acute course of shingles, the drug significantly reduces the intensity of the pain syndrome.
The active substance of the drug penetrates into the cell affected by the virus, where it is converted to monophosphate.This metabolite is transformed into diphosphate with the participation of the enzyme guanylate cyclase.In the next step, an active form of triphosphate is formed - triphosphate, which blocks the process of replication of foreign DNA.
Note: Acyclovir acts selectively without harming the hereditary apparatus of healthy cells.
After oral ingestion of tablets, up to 20% of the active ingredient is absorbed into the gastrointestinal tract.The level of bioavailability varies from 15% to 30%.Up to 33% of the drug is conjugated to serum proteins.The greatest concentration in the blood is fixed in most cases after a half to two hours after taking Acyclovir tablets, and the half-life is about 3 hours.Both unchanged substance and its metabolites are excreted mainly in urine;Only about 2% are excreted by the intestine.
After laying the ophthalmic ointment, the active ingredient freely penetrates the epithelium of the cornea.Due to this, a therapeutic concentration is created in the intraocular fluid.
Ointment for external use also easily penetrates through the epithelium of the skin and mucous membranes.
After topical application, acyclovir is not absorbed into the blood.
Contraindications Acycledovir and possible side effects
The antiviral drug is tolerated without any problems by the vast majority of patients.Contraindication to the use of Acyclovir is the individual hypersensitivity of the patient's body to the active substance.
In some cases( very rarely) the following side effects are noted:
- allergic reactions;
- headache;
- nausea;
- intestinal disorders;
- shortness of breath;
- abdominal pain.
Against the background of prolonged use of ophthalmic ointment, inflammation of the conjunctiva( conjunctivitis) and eyelids( blepharitis) can not be ruled out.
Frequent excess of therapeutic dosages when taking tablets theoretically can cause renal dysfunction.
Interaction of Acyclovir with other drugs
At present, there is no data on the clinically significant antagonism of Acyclovir with other drugs.The therapeutic effect is enhanced by a parallel intake with drugs that stimulate immunity.
Probenecid is able to slow the process of removing the antiviral agent from the body.
To prevent functional impairment of the kidneys, do not take Acyclovir together with drugs that have nephrotoxic properties.
Can Acyclovir be administered to pregnant and lactating women?
During pregnancy, Acyclovir in tablets should not be used, since the drug that has entered the blood stream will bypass the hematoplacental barrier.Ointment can be used as directed by a doctor.If it is necessary to take
course medication for oral intake during breastfeeding, it is advisable to convert the baby to artificial mixtures.There are no contraindications for the use of the ointment during lactation.
How to store the drug, and what is its expiration date?
Shelf life for both tablets and ointments is 3 years.After the tube is opened, the ointment can be used for a month.
Oily forms should be stored at a temperature between + 15 ° and + 25 ° C.
The tablets should be kept in places that are shielded from sunlight and protected from moisture.
Keep out of the reach of children!
Vladimir Plisov, medical reviewer
