Do NOT use Valtrex if:

• you are allergic to any ingredient in Valtrex or to acyclovir.

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Valtrex. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have had a bone marrow or kidney transplant
• if you have HIV or AIDS
• if you have kidney problems.

Some medicines may interact with Valtrex. However, no specific interactions with Valtrex are known at this time.

Important safety information:

• Valtrex may cause dizziness. This effect may be worse if you take it with alcohol or certain medicines. Use Valtrex with caution. Do not drive or perform other possible unsafe tasks until you know how you react to it.
• Safer sex practices can lower the chances of passing genital herpes to your partner. Do not have sexual contact with your partner when you have any symptoms or outbreak of genital herpes. Use a condom made of latex or polyurethane whenever you have sexual contact.
• Lab tests, including complete blood cell counts, kidney function, and liver function, may be performed while you use Valtrex. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• Use Valtrex with caution in the elderly; they may be more sensitive to its effects, especially kidney and nervous system problems.
• Valtrex should be used with extreme caution in children younger 2 years; safety and effectiveness in these children have not been confirmed.
• Pregnancy and breast-feeding: If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Valtrex while you are pregnant. Valtrex is found in breast milk. If you are or will be breast-feeding while you use Valtrex, check with your doctor. Discuss any possible risks to your baby.

All medicines may cause side effects, but many people have no, or minor, side effects.

Check with your doctor if any of these most common side effects persist or become bothersome:

Dizziness; headache; nausea; stomach pain; vomiting.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); aggressive behavior; bloody or dark urine; change in the amount of urine produced; confusion; depression; fatigue; fever; hallucinations; joint pain; lower back pain; pale skin; painful menstrual periods; pinpoint bruises; seizures; severe abdominal pain; shaky movements; speech problems; swelling of the face, hands, feet, or entire body; unsteady movement; unusual bruising or bleeding from the nose or mouth; weakness; yellowing of the skin or eyes.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.