Valtrex Side Effects

Generic name: valacyclovir

Medically reviewed by Drugs.com. Last updated on Jul 22, 2024.

Note: This document provides detailed information about Valtrex Side Effects associated with valacyclovir. Some dosage forms listed on this page may not apply specifically to the brand name Valtrex.

Applies to valacyclovir: oral tablet.

Serious side effects of Valtrex

Along with its needed effects, valacyclovir (the active ingredient contained in Valtrex) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking valacyclovir:

More common

• discouragement
• feeling sad or empty
• irritability
• lack of appetite
• loss of interest or pleasure
• tiredness
• trouble concentrating
• trouble sleeping

Rare

• 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
• shortness of breath
• yellow eyes or skin

Incidence not known

• actions that are out of control
• agitation
• anxiety
• back, leg, or stomach pains
• bleeding gums
• 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
• 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
• lightheadedness when getting up from a lying or sitting position
• light-colored stools
• loss of consciousness
• mood or mental changes
• nausea and vomiting
• nervousness
• pale color of 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
• 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
• 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
• tightness in the chest
• trembling or shaking of the hands or feet
• trouble in speaking
• troubled breathing
• unsteadiness, trembling, or other problems with muscle control or coordination
• unusual behavior
• unusual bleeding or bruising
• unusual tiredness or weakness
• upper right abdominal pain
• vomiting
• weight gain
• wheezing

Other side effects of Valtrex

Some side effects of valacyclovir may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• body aches or pain
• cramps
• difficulty in moving
• ear congestion
• heavy bleeding
• loss of voice
• muscle aches
• muscle pain or stiffness
• nasal congestion
• pain
• pain in joints
• sneezing
• sore throat
• stuffy or runny nose

Less common

• constipation
• diarrhea

Incidence not known

• blistering, peeling, or loosening of the skin
• hair loss or thinning of the hair
• hives or welts
• increased sensitivity of skin to sunlight
• red, irritated eyes
• redness or other discoloration of the skin
• severe sunburn

For healthcare professionals

Applies to valacyclovir: compounding powder, oral tablet.

General

The most common side effects reported were headache, nausea, and abdominal pain.^[Ref]

Nervous system

Cytomegalovirus (CMV) prophylaxis after renal or heart transplants:

• Very common (10% or more): Headache (up to 57%), somnolence (up to 21%)
• Common (1% to 10%): Dizziness, tremor

Other indications:

• Very common (10% or more): Headache (up to 38%)
• Common (1% to 10%): Dizziness, migraine
• Uncommon (0.1% to 1%): Somnolence
• Frequency not reported: Central nervous system (CNS) effects (including seizures, encephalopathy)
• Postmarketing reports: Seizures/convulsions, tremors, ataxia, coma, decreased consciousness, dizziness, dysarthria, encephalopathy^[Ref]

CNS side effects (including seizures, encephalopathy) have been reported in patients with or without reduced renal function and in patients with preexisting renal disease receiving doses higher than recommended for their level of renal function. Reversible neurological reactions (including dizziness, rarely decreased consciousness, and very rarely tremor, ataxia, dysarthria, convulsions, encephalopathy, coma) have been reported; such events were generally seen in patients with renal dysfunction or other predisposing factors. Neurological reactions occurred more often in organ transplant recipients receiving high doses (8 g/day) for CMV prophylaxis, compared with lower doses. Elderly patients were more likely to have CNS side effects.^[Ref]

Respiratory

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Increased cough (up to 57%), dyspnea (up to 36%)

Other indications:

• Very common (10% or more): Rhinitis (up to 26%), influenza syndrome (up to 20%), nasopharyngitis (up to 16%), pharyngitis (up to 12%)
• Common (1% to 10%): Upper respiratory tract infection, sinusitis, bronchitis, increased coughing
• Frequency not reported: Rhinorrhea
• Postmarketing reports: Dyspnea^[Ref]

Musculoskeletal

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Myalgia (up to 57%), back pain (up to 29%)
• Common (1% to 10%): Arthralgia

Other indications:

• Very common (10% or more): Back pain (up to 12%)
• Common (1% to 10%): Arthralgia, myalgia^[Ref]

Other

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Peripheral edema (up to 50%), asthenia (up to 43%), pain (up to 43%), general edema (up to 21%), chest pain (up to 21%)
• Common (1% to 10%): Fever, edema

Other indications:

• Very common (10% or more): Infection (up to 18%), pain (up to 11%), fever (up to 11%)
• Common (1% to 10%): Fatigue, asthenia, chills, elevated alkaline phosphatase, accidental injury, unevaluable reaction
• Frequency not reported: Abnormal alkaline phosphatase
• Postmarketing reports: Facial edema^[Ref]

Cardiovascular

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Pericardial effusion (up to 43%), hypertension (up to 21%)

Other indications:

• Postmarketing reports: Hypertension, tachycardia^[Ref]

Gastrointestinal

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Nausea (up to 21%), constipation (up to 21%)
• Common (1% to 10%): Diarrhea, abdominal pain, vomiting

Other indications:

• Very common (10% or more): Diarrhea (up to 19%), nausea (up to 16.5%), abdominal pain (up to 12%)
• Common (1% to 10%): Vomiting, constipation, dyspepsia, dry mouth, flatulence, tooth disorder, rectal disorder
• Postmarketing reports: Diarrhea, abdominal discomfort, vomiting^[Ref]

Psychiatric

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Depression (up to 21%), insomnia (up to 21%), sleep disorder (21%)
• Common (1% to 10%): Hallucination, confusion

Other indications:

• Common (1% to 10%): Depression, insomnia, nervousness
• Frequency not reported: CNS effects (including agitation, hallucinations, confusion, delirium)
• Postmarketing reports: Aggressive behavior, agitation, confusion, mania, psychosis, auditory and visual hallucinations, psychotic symptoms^[Ref]

CNS side effects (including agitation, hallucinations, confusion, delirium) have been reported in patients with or without reduced renal function and in patients with preexisting renal disease receiving doses higher than recommended for their level of renal function. Reversible neurological reactions (including confusion, hallucinations) have been reported; such events were generally seen in patients with renal dysfunction or other predisposing factors. Neurological reactions occurred more often in organ transplant recipients receiving high doses (8 g/day) for CMV prophylaxis, compared with lower doses. Elderly patients were more likely to have CNS side effects.^[Ref]

Hematologic

CMV prophylaxis after renal or heart transplants:

• Very common (10% or more): Anemia (up to 12%)
• Common (1% to 10%): Leukopenia, thrombocytopenia

Other indications:

• Very common (10% or more): Decreased neutrophil counts (up to 18%)
• Common (1% to 10%): Decreased WBCs, decreased platelet counts
• Uncommon (0.1% to 1%): Decreased hemoglobin
• Frequency not reported: Abnormal hemoglobin, abnormal WBCs
• Postmarketing reports: Thrombocytopenia, aplastic anemia, leukocytoclastic vasculitis, thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), leukopenia, thrombotic microangiopathy, microangiopathic hemolytic anemia^[Ref]

Decreased WBCs (less than 0.75 times the lower limit of normal [0.75 x LLN]), platelet count (less than 100,000/mm3) and hemoglobin (less than 0.8 x LLN) have been reported in up to 1.3%, up to 1.1%, and up to 0.8% of patients, respectively.

TTP/HUS (in some cases resulting in death) has occurred in patients with advanced HIV-1 disease (including those receiving this drug for prolonged periods), in allogeneic bone marrow transplant recipients, and in renal transplant recipients during clinical trials of this drug at doses of 8 g/day.

Leukopenia was primarily reported in immunocompromised patients.

Renal insufficiency, microangiopathic hemolytic anemia, and thrombocytopenia (sometimes in combination) have been reported in severely immunocompromised patients (especially those with advanced HIV disease) receiving high doses (8 g/day) of this drug for prolonged periods in clinical trials. Such findings have been seen in patients not treated with this drug who had the same underlying/concurrent conditions.^[Ref]

Hepatic

CMV prophylaxis after renal or heart transplants:

• Common (1% to 10%): Increased ALT, increased AST

Other indications:

• Very common (10% or more): Elevated AST (up to 16%), elevated ALT (up to 14%)
• Common (1% to 10%): Abnormal ALT, elevated AST
• Postmarketing reports: Hepatitis, liver enzyme abnormalities, reversible increases in liver function tests^[Ref]

Increased AST (greater than 2 times the upper limit of normal [2 x ULN]) has been reported in up to 4.1% of patients. Abnormal ALT (greater than 2 x ULN) has been reported in 1.8% of patients.^[Ref]

Dermatologic

CMV prophylaxis after renal or heart transplants:

• Common (1% to 10%): Pruritus

Other indications:

• Common (1% to 10%): Rash, acne, pruritus
• Frequency not reported: Herpes simplex
• Postmarketing reports: Erythema multiforme, rashes (including photosensitivity), alopecia, pruritus, urticaria, angioedema, drug reaction with eosinophilia and systemic symptoms (DRESS)^[Ref]

Hypersensitivity

Other indications:

• Common (1% to 10%): Allergic reaction
• Postmarketing reports: Acute hypersensitivity reactions (including anaphylaxis, angioedema, dyspnea, pruritus, rash, urticaria), anaphylaxis^[Ref]

Metabolic

Other indications:

• Common (1% to 10%): Anorexia
• Frequency not reported: Dehydration

Genitourinary

Other indications:

• Common (1% to 10%): Dysmenorrhea, urinary tract infection
• Postmarketing reports: Hematuria^[Ref]

Renal

Other indications:

• Uncommon (0.1% to 1%): Increased serum creatinine
• Frequency not reported: Abnormal serum creatinine
• Postmarketing reports: Renal failure/renal insufficiency, renal pain, renal impairment, acute renal failure, intratubular precipitation of acyclovir (aciclovir) crystals in the kidney^[Ref]

Increased serum creatinine (greater than 1.5 x ULN) has been reported in up to 0.7% of patients.

Renal pain may have been associated with renal failure.

Renal insufficiency, microangiopathic hemolytic anemia, and thrombocytopenia (sometimes in combination) have been reported in severely immunocompromised patients (especially those with advanced HIV disease) receiving high doses (8 g/day) of this drug for prolonged periods in clinical trials. Such findings have been seen in patients not treated with this drug who had the same underlying/concurrent conditions.^[Ref]

Ocular

Other indications:

• Postmarketing reports: Visual abnormalities^[Ref]

Frequently asked questions

• What are the most common skin conditions? (with photos)
• What would be the benefits of taking valacyclovir vs acyclovir?

Further information

Valtrex side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer