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Valtrex Drug Interactions

by on July 2, 2012

Certain drugs and medications are known to interact with Valtrex (valacyclovir),  most of which are moderate or minor interactions.

Significant Drug Interactions

Some drugs that can cause significant drug interactions when taken with Valtrex include:

Antiulcer drugs: Combining Valtrex with antiulcer drugs, particularly cimetidine, can lead to increased blood levels of Valtrex. Usually, the increase in drug levels will not cause any problems as such dose adjustment may not be necessary. However, the risk for side effects may increase if you have impaired kidney function. Discuss with your healthcare provider this drug combination especially if you have kidney problems.

  • cimetidine (Tagamet)

Antigout drugs: Combining Valtrex with antigout drugs, particularly probenecid, can lead to increased blood levels of Valtrex. Usually, the increase in drug levels will not cause any problems as such dose adjustment may not be necessary. However, the risk for side effects may increase if you have impaired kidney function. Discuss with your healthcare provider this drug combination especially if you have kidney problems.

  • probenecid (Benemid)

Antiviral drugs: Taking Valtrex with other antiviral drugs can increase the level of either drug in your blood, causing an increased risk of side effects. Dose adjustments may be necessary. In addition, combining antiviral drugs can lead to serious damage to the liver.

  • adefovir (Hepsera)
  • cidofovir (Vistide)
  • foscarnet (Foscavir)
  • tenofovir (Viread)

Drugs for Herpetic Infections: Valtrex is a ‘prodrug’ of acyclovir which means that the body converts it into acyclovir. Do not take any medication that contains acyclovir while taking Valtrex. It can lead potentially dangerous levels of acyclovir in the blood.

  • acyclovir (Zoverax)

Since Valtrex can cause harm to the kidneys, the risk is further increased when it is combined with other medications that are known to harm the kidneys. Some of the medications that are known to harm the kidneys include:

  • lithium (Eskalith, Lithobid)
  • methotrexate (Rheumatrex, Trexal)
  • pain medications
    • aspirin (Anacin, Excedrin)
    • acetaminophen (Tylenol)
    • diclofenac (Voltaren)
    • ibuprofen (Advil, Motrin)
    • indomethacin (Indocin)
    • naproxen (Aleve, Naprosyn)
  • medications for ulcerative colitis
    • mesalamine (Pentasa)
    • sulfasalazine (Azulfidine)
  • immunosuppressant drugs
    • sirolimus (Rapamune)
    • tacrolimus (Prograf)
  • antibiotics injections
    • amphotericin B (Fungizone, Amphotec)
    • amikacin (Amikin)
    • bacitracin (Baci-IM)
    • capreomycin (Capastat)
    • gentamicin (Garamycin)
    • kanamycin (Kantrex)
    • streptomycin
    • vancomycin (Vancocin, Vancoled)
  • chemotherapeutic agents
    • aldesleukin (Proleukin)
    • carmustine (Gliadel)
    • cisplatin (Platinol)
    • ifosfamide (Ifex)
    • oxaliplatin (Eloxatin)
    • plicamycin (Mithracin)
    • streptozocin (Zanosar)
    • tretinoin (Vesanoid)

This medication guide may not include all drugs that can potentially interact with Valtrex. Be sure to discuss with your healthcare provider or pharmacist all medications (both prescription and nonprescription) that you take to avoid any drug interactions.

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