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Valtrex Side Effects Center
Medical Editor: John P. Cunha, DO, FACOEP<
Valtrex (valacyclovir) is an antiviral medication used to treat infections with herpes zoster (shingles), herpes simplex genitalis (genital herpes), and herpes labialis (cold sores). Valtrex is available in generic form. It is taken as caplets that may be taken with or without food. Side effects of Valtrex may include headache, dizziness, tired feeling, depression, nausea, vomiting, stomach pain, joint pain, menstrual pain, skin rash, stuffy nose, or sore throat.
Probenecid (Benemid) and cimetidine (Tagamet) may reduce the kidney's clearance of Valtrex, leading to higher concentrations in the blood. This may lead to side effects of Valtrex. Valtrex showed no effects on the fetus in animal studies; however, there has been no adequate evaluation of Valtrex or (acyclovir) in pregnant women. Valtrex should only be used during pregnancy when the benefits to the mother outweigh risks to the fetus. The safety of Valtrex in breastfeeding infants has not been established. Methods other than breastfeeding should be considered if Valtrex must be taken while nursing.
Our Valtrex Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Valtrex in Detail - Patient Information: Side Effects
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.
Stop taking valacyclovir and call your doctor right away if you have any of the following signs of a serious side effect that can harm red blood cells:
- fever, easy bruising or bleeding;
- red spots on the skin (not related to herpes or chickenpox);
- bloody diarrhea, vomiting;
- pale or yellowed skin;
- weakness or fainting; or
- urinating less than usual or not at all.
Call your doctor at once if you have any of these other serious side effects:
- pain in your lower back;
- drowsiness, mood changes, increased thirst, loss of appetite, nausea and vomiting;
- swelling, weight gain, feeling short of breath;
- confusion, agitation, aggression, hallucinations, trouble concentrating;
- feeling shaky or unsteady;
- problems with speech or vision; or
- seizure (convulsions).
Less serious side effects may include:
- nausea, stomach pain;
- headache, dizziness, tired feeling, depression;
- joint pain;
- menstrual pain;
- mild skin rash; or
- stuffy nose, sore throat.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
Read the entire detailed patient monograph for Valtrex (Valacyclovir Hydrochloride)
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Valtrex Overview - Patient Information: Side Effects
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: mental/mood changes (such as agitation, confusion, hallucinations), trouble speaking, shaky/unsteady movements, change in the amount of urine.
This medication may rarely cause a life-threatening disorder that affects the blood cells, kidneys, and other parts of the body. This disorder is more likely to occur if you have conditions related to a weakened immune system (such as HIV disease, bone marrow transplant, kidney transplant). Get medical help right away if you have any serious side effects, including: extreme tiredness, slow/fast/irregular heartbeat, easy bruising/bleeding, new fever, bloody/dark urine, severe stomach/abdominal pain, yellowing eyes/skin, sudden vision changes, loss of consciousness, seizures.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Valtrex (Valacyclovir Hydrochloride)
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Valtrex FDA Prescribing Information: Side Effects
The following serious adverse reactions are discussed in greater detail in other sections of the labeling:
- Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome [see WARNINGS AND PRECAUTIONS].
- Acute Renal Failure [see WARNINGS AND PRECAUTIONS].
- Central Nervous System Effects [see WARNINGS AND PRECAUTIONS].
The most common adverse reactions reported in at least 1 indication by greater than 10% of adult subjects treated with VALTREX and observed more frequently with VALTREX compared to placebo are headache, nausea, and abdominal pain. The only adverse reaction reported in greater than 10% of pediatric subjects aged less than 18 years was headache.
Clinical Trials Experience In Adult Subjects
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.
Cold Sores (Herpes Labialis)
In clinical trials for the treatment of cold sores, the adverse reactions reported by subjects receiving VALTREX 2 grams twice daily (n = 609) or placebo (n = 609) for 1 day, respectively, included headache (14%, 10%) and dizziness (2%, 1%). The frequencies of abnormal ALT (greater than 2 x ULN) were 1.8% for subjects receiving VALTREX compared with 0.8% for placebo. Other laboratory abnormalities (hemoglobin, white blood cells, alkaline phosphatase, and serum creatinine) occurred with similar frequencies in the 2 groups.
Initial Episode: In a clinical trial for the treatment of initial episodes of genital herpes, the adverse reactions reported by greater than or equal to 5% of subjects receiving VALTREX 1 gram twice daily for 10 days (n = 318) or oral acyclovir 200 mg 5 times daily for 10 days (n = 318), respectively, included headache (13%, 10%) and nausea (6%, 6%). For the incidence of laboratory abnormalities see Table 2.
Recurrent Episodes: In 3 clinical trials for the episodic treatment of recurrent genital herpes, the adverse reactions reported by greater than or equal to 5% of subjects receiving VALTREX 500 mg twice daily for 3 days (n = 402), VALTREX 500 mg twice daily for 5 days (n = 1,136) or placebo (n = 259), respectively, included headache (16%, 11%, 14%) and nausea (5%, 4%, 5%). For the incidence of laboratory abnormalities see Table 2.
Suppressive Therapy: Suppression of Recurrent Genital Herpes in Immunocompetent Adults: In a clinical trial for the suppression of recurrent genital herpes infections, the adverse reactions reported by subjects receiving VALTREX 1 gram once daily (n = 269), VALTREX 500 mg once daily (n = 266), or placebo (n = 134), respectively, included headache (35%, 38%, 34%), nausea (11%, 11%, 8%), abdominal pain (11%, 9%, 6%), dysmenorrhea (8%, 5%, 4%), depression (7%, 5%, 5%), arthralgia (6%, 5%, 4%), vomiting (3%, 3%, 2%), and dizziness (4%, 2%, 1%). For the incidence of laboratory abnormalities see Table 2.
Suppression of Recurrent Genital Herpes in HIV-1-Infected Subjects: In HIV-1-infected subjects, frequently reported adverse reactions for VALTREX (500 mg twice daily; n = 194, median days on therapy = 172) and placebo (n = 99, median days on therapy = 59), respectively, included headache (13%, 8%), fatigue (8%, 5%), and rash (8%, 1%). Post-randomization laboratory abnormalities that were reported more frequently in valacyclovir subjects versus placebo included elevated alkaline phosphatase (4%, 2%), elevated ALT (14%, 10%), elevated AST (16%, 11%), decreased neutrophil counts (18%, 10%), and decreased platelet counts (3%, 0%), respectively.
Reduction of Transmission: In a clinical trial for the reduction of transmission of genital herpes, the adverse reactions reported by subjects receiving VALTREX 500 mg once daily (n = 743) or placebo once daily (n = 741), respectively, included headache (29%, 26%), nasopharyngitis (16%, 15%), and upper respiratory tract infection (9%, 10%).
In 2 clinical trials for the treatment of herpes zoster, the adverse reactions reported by subjects receiving VALTREX 1 gram 3 times daily for 7 to 14 days (n = 967) or placebo (n = 195), respectively, included nausea (15%, 8%), headache (14%, 12%), vomiting (6%, 3%), dizziness (3%, 2%), and abdominal pain (3%, 2%). For the incidence of laboratory abnormalities see Table 2.
Table 2: Incidence (%) of Laboratory Abnormalities in
Herpes Zoster and Genital Herpes Trial Populations
|Laboratory Abnormality||Herpes Zoster||Genital Herpes Treatment||Genital Herpes Suppression|
|VALTREX 1 gram 3 Times Daily
(n = 967)
(n = 195)
|VALTREX 1 gram Twice Daily
(n = 1,194)
|VALTREX 500 mg Twice Daily
(n = 1,159)
(n = 439)
|VALTREX 1 gram Once Daily
(n = 269)
|VALTREX 500 mg Once Daily
(n = 266)
(n = 134)
|Hemoglobin ( < 0.8 x LLN)||0.8%||0%||0.3%||0.2%||0%||0%||0.8%||0.8%|
|White blood cells ( < 0.75 x LLN)||1.3%||0.6%||0.7%||0.6%||0.2%||0.7%||0.8%||1.5%|
|Platelet count ( < 100,000/mm³)||1.0%||1.2%||0.3%||0.1%||0.7%||0.4%||1.1%||1.5%|
|AST (SGOT) ( > 2 x ULN)||1.0%||0%||1.0%||a||0.5%||4.1%||3.8%||3.0%|
|Serum creatinine ( > 1.5 x ULN)||0.2%||0%||0.7%||0%||0%||0%||0%||0%|
|a Data were not collected prospectively.
LLN = Lower limit of normal.
ULN = Upper limit of normal.
Clinical Trials Experience In Pediatric Subjects
The safety profile of VALTREX has been studied in 177 pediatric subjects aged 1 month to less than 18 years. Sixty-five of these pediatric subjects, aged 12 to less than 18 years, received oral caplets for 1 to 2 days for treatment of cold sores. The remaining 112 pediatric subjects, aged 1 month to less than 12 years, participated in 3 pharmacokinetic and safety trials and received valacyclovir oral suspension. Fifty-one of these 112 pediatric subjects received oral suspension for 3 to 6 days. The frequency, intensity, and nature of clinical adverse reactions and laboratory abnormalities were similar to those seen in adults.
Pediatric Subjects Aged 12 To Less Than 18 Years (Cold Sores)
In clinical trials for the treatment of cold sores, the adverse reactions reported by adolescent subjects receiving VALTREX 2 grams twice daily for 1 day, or VALTREX 2 grams twice daily for 1 day followed by 1 gram twice daily for 1 day (n = 65, across both dosing groups), or placebo (n = 30), respectively, included headache (17%, 3%) and nausea (8%, 0%).
Pediatric Subjects Aged 1 Month To Less Than 12 Years
Adverse events reported in more than 1 subject across the 3 pharmacokinetic and safety trials in children aged 1 month to less than 12 years were diarrhea (5%), pyrexia (4%), dehydration (2%), herpes simplex (2%), and rhinorrhea (2%). No clinically meaningful changes in laboratory values were observed.
In addition to adverse events reported from clinical trials, the following events have been identified during postmarketing use of VALTREX. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to VALTREX.
CNS Symptoms: Aggressive behavior; agitation; ataxia; coma; confusion; decreased consciousness; dysarthria; encephalopathy; mania; and psychosis, including auditory and visual hallucinations, seizures, tremors [see WARNINGS AND PRECAUTIONS, Use In Specific Populations].
Eye: Visual abnormalities.
Hepatobiliary Tract and Pancreas: Liver enzyme abnormalities, hepatitis.
Read the entire FDA prescribing information for Valtrex (Valacyclovir Hydrochloride)
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