Acyclovir is a nucleoside‑analogue antiviral drug that blocks viral DNA replication. It’s used mainly for herpes simplex virus (HSV) infections, varicella‑zoster virus (chickenpox and shingles), and in some cases for Epstein‑Barr virus (EBV) and CMV infections in immunocompromised patients.
Common Brand Names
| Region |
Brand / Trade Name |
Formulation |
| United States |
Valtrex |
Oral tablet (200 mg, 400 mg, 800 mg) |
| United States |
Zovirax |
Topical cream (5 % or 10 %), ointment (5 % or 10 %) |
| United States |
Zovirax |
Oral liquid (100 mg/5 mL) |
| Europe |
Virox |
Oral tablets (200 mg, 400 mg, 800 mg) |
| Europe |
Virox |
Topical gel/cream (5 % or 10 %) |
| Canada |
Acyclovir (generic) |
Oral tablets (200 mg, 400 mg) |
| Australia |
Aciclovir |
Oral tablets (200 mg, 400 mg, 800 mg) |
| Brazil |
Aciclovir |
Oral tablets (200 mg, 400 mg, 800 mg) |
| India |
Aciclovir |
Oral tablets (200 mg, 400 mg, 800 mg) |
| Other countries |
Various generic brand names (e.g., “Aciclovir” in many markets) |
Oral tablets/creams/ointments |
Note: The generic name is acyclovir in most regions. The “generic” version is often sold under the same name but is cheaper.
Typical Indications
| Condition |
Typical Course |
Common Dosage (Adults) |
| Oral/genital herpes |
7–10 days |
200 mg PO, 5×/day or 400 mg PO, 3×/day |
| Shingles (herpes zoster) |
7–10 days |
200 mg PO, 5×/day or 800 mg PO, 3×/day |
| Varicella (chickenpox) |
7–10 days |
200 mg PO, 5×/day or 400 mg PO, 3×/day |
| CMV prophylaxis (post‑transplant) |
60–90 days |
200 mg PO, 5×/day or 400 mg PO, 3×/day |
| Topical application for cold sores |
5 days |
5–10 % cream/gel, applied 5×/day |
(Dosage may differ for children, renal impairment, or pregnancy; always check a current prescribing info sheet.)
Key Safety Points
- Renal Function: Acyclovir is cleared by the kidneys. Dose adjustment is required in chronic kidney disease (CKD) or if creatinine clearance < 50 mL/min.
- Side Effects: Nausea, headache, abdominal pain, vomiting, mild rash. Rarely, nephrotoxicity (especially with intravenous use) or neurotoxicity (confusion, hallucinations) may occur.
- Drug Interactions:
- Cyclosporine: increases acyclovir serum levels.
- Digoxin: may increase digoxin levels (rare).
- Other nephrotoxic drugs (e.g., aminoglycosides) may worsen kidney injury.
- Contraindications: Severe renal impairment (CrCl < 15 mL/min) unless dose adjustment is done; hypersensitivity to acyclovir.
Quick FAQ
| Question |
Answer |
| Is acyclovir still the standard for HSV? |
Yes, it remains first‑line for most uncomplicated HSV infections. |
| Can it be taken with food? |
Yes, food does not affect absorption. |
| Is it safe during pregnancy? |
Category B (US) – generally considered safe, but consult your OB‑GYN. |
| Why is “Valtrex” used instead of generic? |
“Valtrex” is the brand of the oral formulation; the generic acyclovir is typically cheaper. |
| What is the difference between Valtrex and Zovirax? |
Valtrex is oral; Zovirax is topical or oral liquid. |
How to Store
- Oral tablets: Keep in a cool, dry place. Do not expose to moisture.
- Topical cream/gel: Store at room temperature (≤ 25 °C). Keep away from direct sunlight.
- Oral liquid: Refrigerate after opening. Shake well before each dose.
When to Seek Medical Attention
- Persistent high fever, seizures, or severe abdominal pain.
- Signs of kidney impairment (e.g., decreased urine output, swelling).
- Severe allergic reaction (rash, itching, swelling, difficulty breathing).
Bottom line: Acyclovir (under many brand names such as Valtrex, Zovirax, Virox, or Aciclovir) is a reliable antiviral for HSV, varicella, and shingles, with a good safety profile when renal function is considered. If you’re prescribed it, follow the dosing schedule, monitor kidney function if needed, and report any unusual side effects.