Acyclovir (Aciclovir)

Acyclovir. Acivir

Acyclovir (acivir) is an antiviral agent (virostatic), an acyclic analogue of guanine, natural component of DNA, a synthetic nucleoside analogue of thymidine. The enzyme thymidine kinase of infected by virus cells actively converts (by phosphorylation) Acyclovir into its more active forms Acyclovir triphosphate. Acyclovir triphosphate penetrates the infected cells and inhibits the enzyme called  DNA-polymerase and  competitive substitutes deoxyguanosine triphosphate in the synthesis of DNA viruses. Acyclovir embeds into viral DNA and blocks viral replication. 

The high selectivity and low toxicity to humans is associated with absence of thymidine kinase in healthy cells of macroorganism. Therefore acyclovir does not act on healthy human cells.

Acyclovir is active against herpes simplex virus Herpes simplex types 1 and 2, the virus that causes chickenpox, Varicella zoster, Epstein-Barr virus. Acylcovir oral possesses moderate activity against cytomegalovirus.
In Herpes Simplex infection, Acyclovir prevents the formation of new rash elements,  reduces the likelihood of cutaneous dissemination and visceral complications, speeds up the formation of crusts, reduces pain in the acute phase of herpes zoster infection.

After oral administration nearly 20% of acyclovir is absorbed into the blood circulation. Only a small amount of acyclovir binds to plasma proteins by 9-33%. Acyclovir penetrates placental barrier and is found in breast milk. The metabolite of acyclovir is 9-(carboxy methoxymethyl) guanine. Acyclovir is excreted with urine in unchanged form and in the form of metabolite (10-15%). The average half life period is 3 hours.

 Indication

• Treatment of infections of skin and mucous membranes caused by Herpes simplex virus types 1 and 2, both primary and recurrent (including herpes labialis, genital herpes, acute primary genital infection).
• Treatment of infections caused by viruses Varicella zoster (including chickenpox, shingles, herpes zoster).
• Treatment and prevention of infections of skin and mucous membranes caused by Herpes simplex virus types 1 and 2 in patients with immunodeficiencies.
• Prevention of diseases caused by the virus Herpes simplex, after transplantation.
• Oral acyclovir can also be used for encephalitis and herpes eczema

Acyclovir comes in the form of tablets 200mg, 400mg, 800mg. Tablets should be taken whole swallowing with sufficient amount of water. Do not crash or split the tablets unless is prescribed by your doctor. The recommended dose for treatment of Herpes simplex infection type 1 and 2 is 200mg 5 times daily (every 4 hours) for a period of 5 days. Try to take the medication at the same time each day to maintain the constant level of medication in your blood.

Contraindications

• Known reactions of hypersensitivity to allergy to acyclovir or valacyclovir (Valtrex)
• Severe kidney diseases (renal failure, acute glomerulonephritis, pyelonephritis)
• Liver diseases in active phase
• Treatment of infections caused by bacteria or fungi
• Pregnancy  (acyclovir is a pregnancy category B meaning that is probably safe to use the medication during pregnancy. However, there are no clinical data confirming the safety of acyclovir for pregnant women)
• Breastfeeding (acycolvir can pass through breast milk)

Acyclovir oral can cause renal damage. Make sure to consult your doctor if you develop any kidney dysfunction during the treatment.

In very rare cases Acyclovir may cause thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). This conditions is characterized by very low platelets and erythrocytes blood levels.  If you develop unusual bruising, hemorrhage or unexplained fever seek immediate medical attention.

Acyclovir oral does not cure genital herpes. It helps only to relieve the symptoms of the disease. You need to avoid sexual intercourse during the treatment.

Try to begin taking Acyclovir oral as soon as the first symptoms occur. It's much more effective if treatment starts at the beginning of the disease.
Acyclovir oral tablets should be used with caution in elderly patients.

Side effects

• Digestive system: nausea, vomiting, diarrhea, abdominal pain, reversible increase in bilirubin and liver enzymes.
• Hemopoietic system: anemia, leukopenia, thrombocytopenia.
• Urinary system: increasing urea and creatinine in blood, renal failure in rare cases
• Central nervous system: headache, reversible neurological disorders, dizziness, confusion, hallucinations, drowsiness, convulsions, coma. Typically, these side effects were observed in patients with renal insufficiency who took the drug in doses exceeding recommended.
• Allergic reactions: rash, photosensitivity, urticaria, pruritus, in rare cases - shortness of breath, angioedema, anaphylaxis.
• Other: fatigue; alopecia

Drug interaction

• Acyclovir may increase blood levels of Phenytoin and increase the risk of side effects
• Uricosuric drug Probenicid may increase Acyclovir blood levels
• Acyclovir may increase blood levels of antiviral drug tenofovir