Acyclovir

What is acyclovir?

Acyclovir is the most prescribed. antiviral drugs in the world. It first became available by prescription in 1983.

Acyclovir is a synthetic compound with a similar molecular structure to purinate nucleosides. It has been shown to stop the growth of herpes simplex virus (HSV), varicella zoster virus (VZV) (the cause of chickenpox and shingles), Epstein-Barr virus (EBV, the cause of glandular gland). fever), and to a lesser extent Cytomegalovirus (CMV).

Indications for treatment with acyclovir.

Acyclovir is used to treat:

• Primary Herpes Simplex
• Recurrent episodes of genital herpes
• Suppression of HSV infections
• The first days of shingles infections.

Dosing regimens for acyclovir

Herpes Simplex

• For an initial outbreak in adults and children over 2 years of age, oral acyclovir 200 mg, or 400 mg three times a day, five times a day for 10 days, should be taken. Half the adult dose should be used for children under 2 years of age.
• For recurrent episodes, treatment should be started as soon as possible. sign and continued for 5 days.
• If long-term suppressive therapy is necessary, 400 mg twice daily is administered.

Acyclovir is also available as a cold sore cream for lips and face, and as an ophthalmic ointment for eye infections. Should be applied at the first sign of recurring infection, often a tingling sensation. It is then rubbed into the affected area every four hours during waking hours for 5 days. Not suitable for use inside the mouth or other mucous membranes

Varicella zoster

Acyclovir is an important treatment for Herpes zoster (shingles), but it can also be used to treat chickenpox (chickenpox) in adults or serious infections in children.

The best results are achieved if treatment begins within 48 hours of the start of the procedure. eruption. Oral acyclovir 800 mg five times a day for 7 days accelerates the rate of healing of blisters. In zoster infections, it also reduces the severity and duration of pain and may prevent postherpes. neuralgia.

Intravenous acyclovir achieves higher blood levels compared to oral acyclovir. It is recommended for serious infections:

• Immunocompromised patients with chickenpox, disseminated herpes zoster or severe herpes simplex
• Acute herpes zoster when it affects the trigeminal nerve (forehead and eyelids)
• Extensive eczema herpetic
• Herpes infection of the brain (encephalitis)
• Herpes infections in newborns.

Intravenous acyclovir is administered over 1 hour every 8 hours for 7 days at a dose of 5 mg/kg for HSV and 10 mg/kg for VZV.

Mechanism of action of acyclovir.

To be effective, acyclovir must first be switched to acyclovir monophosphate for a enzyme that is only found in viruses, called thymidine kinase (TK). It is then converted to its active triphosphate form by humans. enzymes found inside cells.

CMV does not produce thymidine kinase, so the antiviral activity of acyclovir in CMV infections is poor.

Acyclovir triphosphate (AT) is the active form of the medication. Reduces virus production DNA by competing with a natural compound, deoxyguanosine triphosphate, for the viral enzyme DNA polymerase. Incorporation of AT into viral DNA completely prevents the synthesis of new DNA.

Viral DNA polymerase binds 10 to 30 times more strongly to AT than cellular DNA polymerase. This means that acyclovir is not toxic.

Unfortunately, only about 15-20% of the acyclovir dose is absorbed through the intestinal wall, meaning it must be taken frequently as it is only active for two to three hours in the bloodstream.

Acyclovir Side Effects

Side effects are rare from acyclovir, but include nausea or vomiting, diarrhea, headache, fever, confusion, lymphadenopathy, generalized muscle pain and itchy skin.

Acyclovir should be used with caution in patients with kidney disease. The dose should be reduced to prevent buildup of the medication and decrease the risk of the medication damaging the kidneys or nervous system. Acyclovir may also cause abnormal liver function blood tests and, rarely, a decrease in white blood cell count.

A pregnancy registry of more than 1,000 women who received acyclovir before or during early pregnancy did not show increased rates of miscarriage or birth defects in offspring. However, as with any medication, it should only be given during pregnancy if the benefits are believed to outweigh the risk.

Other antiviral agents used in herpes infections

Valacyclovir is a prodrug of acyclovir and has better bioavailability. It can also be used to treat HSV and HZV. It is used to prevent CMV infection after an organ transplant. The usual doses are:

• HZV: 1 g three times a day for 7 days.
• HSV: 500 mg twice daily for 5 days.

Famciclovir is used for HSV and HZV. The usual doses are:

• HZV: 500 mg three times a day for 10 days.
• HSV: 125–250 mg three times a day for 5 days
• Long-term suppression: 250 mg twice daily
• Recurrent HSV of the lips: a single dose of 500 mg at the first signs of blisters
• Recurrent genital HSV: 100 mg twice daily for 1 day at the first signs of blisters.