How Effective Is Valacyclovir for Herpes?

Valacyclovir (Valacyclovir) is a guanine analogue antiviral drug used clinically for the treatment of herpes simplex and shingles infections in sexually transmitted diseases. It is a prodrug of acyclovir and can be converted into acyclovir in the body.

Chinese name: Valacyclovir
Foreign name: Valacyclovir

Exterior: White to off-white crystalline powder
Drug classification: Antiviral drugs

Valacyclovir Basic Information

Chinese name: VAcyclovir

Chinese alias: Wannellovir

English name: Valacyclovir

English alias: L-Valine 2- (guanin-9-ylmethoxy) ethyl ester

CAS number: 124832-26-4

Molecular formula: C ₁₃ H ₂₀ N ₆ O ₄

Molecular weight: 324.33600

Exact mass: 324.15500

PSA: 151.14000

LogP: 0.48390

Physical and chemical properties of valacyclovir

Appearance and properties: white to off-white crystalline powder

Density: 1.55 g / cm ³

Flash point: 309.7ºC

Valacyclovir safety properties

Customs code: 3002909099 ^[1]

Related drug leaflet information for valacyclovir

Pharmacological effects of valacyclovir

This product is a prodrug of acyclovir, which is the hydrochloride salt of acyclovir and valine. After oral absorption, it can be quickly and completely converted into acyclovir. In virus-infected cells, it is activated by deoxyglycoside kinase and further phosphorylated into triphosphate. By inhibiting DNA polymerase, and under the action of DNA polymerase, The growing DNA strands bind and terminate the virus's replication, thereby achieving antiviral effects. This product has a broad antiviral spectrum and has a strong inhibitory effect on herpes zoster virus, herpes simplex virus, EB virus and cytomegalovirus, with significant curative effects.

Pharmacokinetics

This drug has good water solubility. After oral absorption, it is rapidly hydrolyzed into acyclovir by hydrolase in the liver. Valacyclovir cannot be detected in the plasma, but the plasma concentration of acyclovir is very high. Compared with lovir, and 3 to 5 times higher than oral acyclovir. The bioavailability of this medicine is 65%, which is significantly higher than that of acyclovir. Taking it after meals does not affect its bioavailability. The drug and plasma protein binding rate is 13.5% to 17.9%, which can be secreted by milk. The catabolism of this drug is carried out in the liver and intestinal wall. Due to the rapid decomposition into acyclovir, the half-life of this drug is less than 30min, while the half-life of acyclovir is about 3h at normal renal function. It is widely distributed in 14 tissues throughout the body, and can reach small intestine, liver, kidney and other tissues, especially the highest concentration in lymph nodes and skin, and the lowest concentration in brain tissue. It can be cleared from all tissues after 24 hours, and the entire dose is excluded from urine and feces after 48 hours. Metabolites are mainly eliminated from the urine. Among them, acyclovir accounts for 46% to 59%, and 8-hydroxyaciclovir accounts for 25% to 30%. After oral and intravenous injection of the same prodrug, unmetabolized prodrugs accounted for 0.5% and 6%, respectively, indicating that the drug is more suitable for oral administration. The blood concentration is close to the intravenous infusion of ACV, and the toxic effect on the kidney is also lighter, which can shorten the time of postherpetic neuralgia faster.

medicine interactions

1. Combined with cimetidine, it can increase the risk of poisoning with this drug, especially when renal insufficiency occurs. 2. Combined with probenecid, it can increase the risk of poisoning of this medicine, especially when renal insufficiency occurs.

Dosage form and specifications

Tablets: 100mg, 125mg, 200mg, 300mg, 500mg.

Valacyclovir indication

Applicable to diseases of viral infection, such as herpes simplex, chicken pox, shingles, initial and recurrent genital herpes, hepatitis, viral meningitis, etc., and can be used to prevent immune damage and immunosuppressive patients such as acquired immunity Defective Syndrome (AIDS), Viral Infection in Organ Transplant Patients. Under the guidance of a doctor, this product can be used for all indications of acyclovir (such as viral hepatitis B, herpes zoster, etc.) primary genital herpes, shingles.

Valacyclovir contraindications

1. People who are allergic to this medicine and acyclovir. 2. Pregnant women. Children under 3.2 are disabled.

Valacyclovir precautions

1. Use with caution: (1) renal insufficiency; (2) lactating women; (3) not recommended for immunodeficiency patients. 2. Cross-allergy: People who are allergic to other guanine antiviral drugs (such as acyclovir, ganciclovir, famciclovir) can also be allergic to this drug. 3. The effect of the drug on pregnancy: This drug is not teratogenic to animals, but the Centers for Disease Control and Prevention does not recommend this drug to pregnant women to treat genital herpes simplex infection and other sexually transmitted diseases.

Valacyclovir adverse reactions

The incidence of adverse reactions is similar to that of acyclovir. Headache, nausea, diarrhea, abdominal pain, fatigue and other reactions are common, but it does not cause changes in blood routine, liver and kidney function. According to domestic reports, due to the small dosage of this product, the incidence of adverse reactions is lower than the latter. The incidence of adverse reactions of the two drugs is 3.47% and 6.32%, respectively. Elevated ALT, AST, rash, urticaria, and occasional renal impairment may be seen when using this product. It has been reported that some patients with severely impaired immune function may develop thrombocytopenic purpura after using high doses of this product . In patients with initial (n = 323) or relapsed (n = 1618) genital herpes, the product is administered orally 0.5 to 1 g twice a day, twice daily for 5 to 10 days. Common adverse reactions are headache, nausea and diarrhea, 2% The above-mentioned patients have the characteristics of mild and low incidence of adverse reactions, and there is no significant difference in the incidence of adverse reactions between oral administration of this product and placebo (n = 259). 1. Digestive system: A few have mild gastrointestinal symptoms, such as upset stomach, loss of appetite, nausea, vomiting, abdominal pain, diarrhea, constipation, etc. 2. Nervous / mental system: headache, fatigue, dizziness. 3. Blood system: can cause anemia, leukopenia, granulocytopenia, thrombotic thrombocytopenic purpura. 4. Urinary system: can cause renal dysfunction. 5. Cardiovascular system: arrhythmia, tachycardia, vasodilation. 6. Others: itchy skin, joint pain, myalgia, photophobia, eye pain.

Valacyclovir dosage

Oral: 1. Herpes zoster: 0.3g each time, 2 times a day for 10 consecutive days, the total dosage is 6g (minimum dosage is 1.8g, treatment course is 3 days). 2. Herpes simplex: 0.3g each time, 2 times a day for 7 consecutive days, the total dosage is 4.2g (minimum dosage is 1.8g, treatment course is 3 days). 3. Genital herpes: 0.3g each time, twice a day for 5 to 10 days. 4. Condyloma acuminatum: 0.3g each time, twice a day for 9 to 27 days ^[2] .