April 26, 2017
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(acyclovir) Tablets, Capsules, and Suspension



Route of Administration Dosage Form / Strength Clinically Relevant Non-medicinal Ingredients
Oral Oral suspension 200 mg/5 mL Tablets 200 mg ZOVIRAX® 200 mg Tablets contain lactose. For a complete listing see Dosage Forms, Composition and Packaging section.

Drug Substance

Proper name: acyclovir

Chemical name: 9-[(2-hydroxyethoxy)methyl]guanine

Other name: acycloguanosine

Molecular formula: C8H11N503

Molecular mass: 225.2 Structural formula:

ZOVIRAX® (Acyclovir) - Structural Formula Illustration

Physicochemical properties: Acyclovir is a white, crystalline powder with a maximum solubility in water of 1.3 mg/mL at 25°C.

What are the possible side effects of acyclovir (Zovirax)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

  • pain in your lower back;
  • urinating less than usual or not at all;
  • easy bruising or bleeding; or
  • unusual weakness.

Less serious side effects may include:

  • nausea, vomiting, diarrhea, loss of appetite, stomach pain;
  • headache, feeling light-headed; or
  • swelling in your hands or...

Read All Potential Side Effects and See Pictures of Zovirax »

What are the precautions when taking acyclovir (Zovirax)?

Before taking acyclovir, tell your doctor or pharmacist if you are allergic to it; or to valacyclovir; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney problems, conditions related to a weakened immune system (such as HIV disease, bone marrow transplant, kidney transplant).

This drug may rarely make you dizzy or drowsy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.

Before having surgery, tell your doctor or dentist about all...

Read All Potential Precautions of Zovirax »

Last reviewed on RxList: 1/7/2016
This monograph has been modified to include the generic and brand name in many instances.

Zovirax - User Reviews

Zovirax User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Zovirax sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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