Zovirax Side Effects: Common Issues and Red Flags

Zovirax (acyclovir) is a widely used antiviral for cold sores, genital herpes, and shingles. It comes as a cream, oral tablet, and IV solution. Side effects differ by form. The cream mostly causes local irritation. Pills and IV can cause systemic effects. Here’s a straight-to-the-point look at what you might feel and when to act.

Common, mild side effects

Topical Zovirax: burning, stinging, redness, dryness, or mild itching where you apply it. These usually fade after a few uses.

Oral Zovirax: nausea, vomiting, diarrhea, headache, dizziness, and tiredness are the most reported issues. They’re usually short-lived and go away after treatment ends.

IV acyclovir can cause similar symptoms plus local irritation at the infusion site. Doctors monitor patients closely when it’s given into a vein.

Serious side effects and warning signs

Kidney problems are the most important serious risk. Acyclovir can crystallize in the kidneys if you’re dehydrated or already have kidney disease. Watch for dark urine, much less urine, swelling in legs, or sudden fatigue. If you notice these, contact a doctor right away.

Mental changes are rare but possible, especially in older adults or those with kidney issues. Confusion, hallucinations, tremors, or seizures need urgent medical attention.

Allergic reactions can occur. Seek emergency care for hives, swelling of face or throat, or trouble breathing.

Other lab changes like low blood cell counts or abnormal liver tests are uncommon but checked if you’re on long or IV treatment.

Who’s at higher risk? People with chronic kidney disease, the elderly, anyone dehydrated, and those taking other nephrotoxic drugs (for example, certain antibiotics or cyclosporine). Probenecid and some drugs that affect kidney clearance can raise acyclovir levels. Tell your provider about all medicines you take.

Practical safety tips you can use today:

• Stay well hydrated while on acyclovir—drink enough water unless your doctor tells you otherwise.
• Take oral medicine with a full glass of water; follow the exact dose and schedule your prescriber gave you.
• Use cream only on external skin. Don’t put it in eyes or mouth. Stop if severe irritation appears.
• If you have kidney problems, your provider may lower the dose or check kidney tests during treatment.
• Report any sudden change in behavior, reduced urine, or severe rash right away.

Pregnancy and breastfeeding: acyclovir is often used in pregnancy when needed, but discuss risks and benefits with your doctor. For babies and older adults, dosing adjustments are common, so follow professional advice closely.

If you’re unsure about a symptom or drug interaction, call your healthcare provider. A quick question can prevent a serious problem. Zovirax helps many people, and with simple precautions you can keep side effects to a minimum.