valacyclovir hydrochloride

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valacyclovir hydrochloride (valaciclovir (UK))

Apo-Valacyclovir, Valtrex

Pharmacologic class: Acyclic purine nucleoside analog

Therapeutic class: Antiviral

Pregnancy risk category B

Action

Rapidly converts to acyclovir, which interferes with viral DNA synthesis and replication

Availability

Caplets: 500 mg, 1 g

Indications and dosages

Herpes zoster (shingles)

Adults: 1 g P.O. t.i.d. for 7 days. Therapy should begin at first sign or symptom of herpes zoster, within 48 hours of onset of zoster rash.

Genital herpes

Adults: For initial episode, 1 g P.O. b.i.d. for 10 days. For recurrent episodes, 500 mg P.O. b.i.d. for 3 days. For chronic suppression, 1 g P.O. daily for no more than 1 year; in patients with history of fewer than nine yearly recurrences, 500 mg P.O. daily for no more than 1 year.

To reduce risk of genital herpes in immunocompetent patients

Adults: 500 mg P.O. daily for source partner, along with counseling regarding safe sex practices

Herpes labialis

Adults: 2 g b.i.d. for 1 day taken 12 hours apart. Begin therapy at first symptom of lesion.

Dosage adjustment

• Renal impairment

Off-label uses

• Cytomegalovirus prophylaxis

Contraindications

• Hypersensitivity to drug, its components, or acyclovir

Precautions

Use cautiously in:
• renal impairment, concurrent use of nephrotoxic drugs, inadequately hydrated patients
• elderly patients
• pregnant or breastfeeding patients
• children.

Administration

• Be aware that therapy may be ineffective if begun more than 72 hours after initial genital herpes outbreak, or more than 24 hours after symptom onset in herpes recurrence.

Adverse reactions

CNS: headache, dizziness, depression, agitation, hallucinations, confusion, encephalopathy

GI: nausea, vomiting, diarrhea, abdominal pain

GU: dysmenorrhea, acute renal failure

Hematologic: anemia, leukopenia, thrombocytopenia, hemolytic uremic syndrome/thrombotic thrombocytopenic purpura/(HUS/TTP)

Musculoskeletal: joint pain

Other: hypersensitivity reaction

Interactions

Drug-drug.Cimetidine, probenecid: increased valacyclovir blood level

Drug-diagnostic tests.Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase: increased levels

Patient monitoring

Monitor CBC. Stay alert for signs and symptoms of blood dyscrasias. Discontinue drug if clinical signs and symptoms and laboratory findings consistent with HUS/TTP occur.
• Assess liver and kidney function tests.

Patient teaching

• Inform patient that herpes transmission can occur even when he is asymptomatic.
• Tell patient and significant other that no cure exists for herpes. Urge them to practice safe sex.
• Inform pregnant patient of risk of neonatal herpes infection.
• Instruct pregnant patient or female of childbearing age to tell health care provider that she has herpes. After delivery, tell her to inform neonatal care providers.

Instruct patient to promptly report unusual bleeding or bruising, urinary changes, or serious adverse CNS reactions.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.

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