Zovirax (acyclovir) and Valtrex (valacyclovir) are antiviral medications commonly prescribed to treat infections caused by certain viruses, including:
- Herpes zoster, the virus responsible for chickenpox and shingles
- Herpes simplex, which causes cold sores and genital herpes
Mechanism of Action
Viruses attack by taking over a cell’s nucleus, forcing it to make viral DNA instead of normal cellular DNA. Acyclovir works as a nucleoside analog, mimicking the nucleoside guanosine. When acyclovir replaces guanosine in viral DNA, it halts DNA replication, effectively stopping the virus.
Valacyclovir converts into acyclovir in the body, allowing it to be taken less frequently than acyclovir.
Effectiveness
Both medications are most effective when started as early as possible after symptoms appear, ideally within 72 hours.
Forms and Dosages
Acyclovir:
- Oral Forms:
- Tablet
- Capsule
- Suspension
- Liquid
- Oral Dosages:
- Chickenpox: 800 mg four times per day for five days
- Genital herpes or cold sores: 200 mg five times a day for ten days
- Shingles: 800 mg five times a day for 7 to 10 days
- Injectable Form:
- Given intravenously, usually in hospital settings, for severe infections affecting the brain.
- Topical Form:
- Cream or ointment: Applied to lip or genital lesions five times per day for four days
Valacyclovir:
- Form:
- Tablet
- Dosages:
- Chickenpox: Dose determined by patient’s weight, usually not over 1000 mg three times a day
- Cold sores: 1000 mg twice a day for one day
- Genital herpes: 1000 mg twice a day for ten days
- Shingles: 1000 mg three times a day for ten days
Acyclovir vs. Valacyclovir: Conclusion
Neither acyclovir nor valacyclovir cures viral infections, but both treat the symptoms and discomfort of acute herpes infections. They also reduce the period during which patients are contagious.Did you know? QuickMD can treat viral infections from the comfort of your home and provide you with an online prescription for valacyclovir (or acyclovir).
