Valtrex (Valtrex)
Antiviral Treatment
Valacyclovir is used to treat cold sores (herpes labialis), shingles (herpes zoster), and genital herpes. It is also used to control genital herpes outbreak in patients with human immunodeficiency virus-1 (HIV-1). This medicine is also used to treat cold sores and chickenpox in children.
Table of Contents
Valtrex Product Information
Valacyclovir is used to treat cold sores (herpes labialis), shingles (herpes zoster), and genital herpes. It is also used to control genital herpes outbreak in patients with human immunodeficiency virus-1 (HIV-1).
This medicine is also used to treat cold sores and chickenpox in children.
In your body, valacyclovir becomes the anti-herpes medicine, acyclovir. Although valacyclovir will not cure shingles or genital herpes, it does help relieve the pain and discomfort and helps the sores heal faster.
This medicine is available only with your doctor\'s prescription.
In your body, valacyclovir becomes the anti-herpes medicine, acyclovir. Although valacyclovir will not cure shingles or genital herpes, it does help relieve the pain and discomfort and helps the sores heal faster.
Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. If you are taking valacyclovir for the treatment of chickenpox, cold sores, shingles, or genital herpes, it is best to start taking valacyclovir as soon as possible after the first sign of the rash or blisters appear, usually within one day. This medicine comes with a patient information leaflet. Read and follow the instructions carefully. Ask your doctor if you have any questions. You may take this medicine with or without food. Drink extra fluids so you will pass more urine while you are using this medicine. This will keep your kidneys working well and help prevent kidney problems. To help clear up your infection, keep taking valacyclovir for the full time of treatment, even if your symptoms begin to clear up after a few days. Do not miss any doses. However, do not use this medicine more often or for a longer time than your doctor ordered.
Valacyclovir starts working as soon as it's taken, with noticeable effects on symptoms like cold sores within 2-3 days.
The effects of valacyclovir can reduce the duration of cold sore outbreaks by approximately one day, and contribute to lesion healing within 4 days for 3-5 day regimens.
Valtrex Quick View
| Active Ingredient | Valacyclovir (becomes acyclovir in the body) |
|---|---|
| Manufacturer | GlaxoSmithKline |
| Type | Antiviral (Anti-herpesvirus agent) |
| Onset | Within 1-3 hours (peak therapeutic concentrations), with noticeable effects within 2-3 days. |
| Duration | The drug is eliminated from the body within 13-18 hours, but its effects on viral replication can last longer, contributing to faster healing. |
| Food Interaction | Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco. |
| Alcohol | Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco. |
| Prescription | Prescription only |
Valtrex Side Effects
Common Side Effects
- Discouragement
- Feeling sad or empty
- Irritability
- Lack of appetite
- Loss of interest or pleasure
- Tiredness
- Trouble concentrating
- Trouble sleeping
- Body aches or pain
- Cramps
- Difficulty in moving
- Ear congestion
- Heavy bleeding
- Loss of voice
- Muscle pain or stiffness
- Pain
- Sneezing
- Stuffy or runny nose
Uncommon Side Effects
- Constipation
- Diarrhea
- Hair loss or thinning of the hair
- Increased sensitivity of skin to sunlight
- Redness or other discoloration of the skin
- Severe sunburn
Rare Side Effects
- Black, tarry stools
- Chest pain
- Chills
- Cough
- Decreased frequency or output of urine
- Fever
- Flu-like symptoms
- Headache
- Lower back or side pain
- Reduced mental alertness
- Trouble breathing
- Yellow eyes or skin
- Actions that are out of control
- Agitation
- Anxiety
- Back, leg, or stomach pains
- Bleeding gums
- Blistering, peeling, or loosening of the skin
- Blood in urine or stools
- Blurred vision
- Change in consciousness
- Change in mental status
- Changes in behavior, especially in interactions with other people
- Changes in patterns and rhythms of speech
- Chest pain or tightness
- Dark or bloody urine
- Difficult or labored breathing
- Difficulty speaking
- Difficulty swallowing
- Dizziness
- Drowsiness
- Dry mouth
- Fast, pounding, or irregular heartbeat or pulse
- Feeling that others are watching you or controlling your behavior
- Feeling that others can hear your thoughts
- Feeling, seeing, or hearing things that are not there
- General tiredness and weakness
- Hyperventilation
- Increased thirst
- Itching
- Joint or muscle pain
- Lightheadedness when getting up from a lying or sitting position
- Light-colored stools
- Loss of consciousness
- Mood or mental changes
- Nausea and vomiting
- Nervousness
- Painful or difficult urination
- Pale skin
- Pinpoint red spots on the skin
- Pounding in the ears
- Puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
- Red irritated eyes
- Red skin lesions, often with a purple center
- Redness of the skin
- Restlessness
- Seeing, hearing, or feeling things that are not there
- Seizures
- Severe mood or mental changes
- Shakiness and unsteady walk
- Shakiness in the legs, arms, hands, or feet
- Skin rash
- Slurred speech
- Sore throat
- Sores, ulcers, or white spots on the lips or in the mouth
- Stiff neck
- Swelling of the face, fingers, or lower legs
- Swollen or painful glands
- Talking, feeling, and acting with excitement
- Trembling or shaking of the hands or feet
- Trouble in speaking
- Unsteadiness, trembling, or other problems with muscle control or coordination
- Unusual behavior
- Unusual bleeding or bruising
- Unusual tiredness or weakness
- Upper right abdominal or stomach pain
- Vomiting
- Weight gain
Important Warning: Check with your doctor immediately if any of the following side effects occur: Discouragement, feeling sad or empty, irritability, lack of appetite, loss of interest or pleasure, tiredness, trouble concentrating, trouble sleeping, black, tarry stools, chest pain, chills, cough, decreased frequency or output of urine, fever, flu-like symptoms, headache, lower back or side pain, reduced mental alertness, trouble breathing, yellow eyes or skin. Also, check with your doctor right away if you have bloody urine, decreased amount of urine, increased thirst, lower back or side pain, loss of appetite, nausea or vomiting, swelling of the face, fingers, or lower legs, trouble breathing, or weight gain. These may be symptoms of serious kidney problems. This medicine may cause nervous system problems. Check with your doctor right away if you have aggressive behavior, confusion, coma, hallucinations, shaky movements, speech problems, or unsteady movement. This medicine may cause serious skin reactions, including acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis. Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, fever, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots on the lips or in the mouth, swollen glands, trouble breathing, unusual bleeding or bruising, or unusual tiredness or weakness.
More Information About Valtrex
Storage
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing. Keep out of the reach of children. Do not keep outdated medicine or medicine no longer needed. Ask your healthcare professional how you should dispose of any medicine you do not use. Store the oral liquid in the refrigerator. Throw away unused oral liquid after 28 days.
Contraindications
Allergies to valacyclovir or acyclovir. Use with caution in patients with bone marrow transplant, HIV or AIDS, kidney transplant, or severe skin reactions to valacyclovir or acyclovir. Kidney disease (eg, patients receiving dialysis) may require a dose adjustment.
Drug Interactions
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases: Dichlorphenamide, Emtricitabine, Fexinidazole, Foscarnet, Leflunomide, Mycophenolate Mofetil, Nitisinone, Tenofovir Alafenamide, Teriflunomide, Vadadustat. Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you: Fosphenytoin, Phenytoin, Valproic Acid.
Valtrex FAQs
Valacyclovir (Valtrex) is an antiviral medication used to treat infections caused by herpes simplex virus (cold sores, genital herpes) and varicella zoster virus (shingles, chickenpox).
Valacyclovir starts working as soon as you take it. For cold sores, it can reduce the duration of the outbreak by about one day, with noticeable effects within 2-3 days. For shingles, it typically takes about 2 to 3 days to make a noticeable difference in symptoms.
It is generally advised to discuss the use of alcohol with your healthcare professional while taking Valacyclovir. When taken together, Valacyclovir and alcohol can increase symptoms such as dizziness, drowsiness, impaired judgment, and coordination problems.
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Content last updated: 14 Apr 2026
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