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INTRODUCTION

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valacyclovir (val-a-sye-kloe-veer)

Valtrex

Classification

Therapeutic: antivirals

Pharmacologic: purine analogues

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Indications
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Treatment of herpes zoster (shingles). Treatment/suppression of genital herpes. Reduction of transmission of genital herpes. Treatment of chickenpox. Treatment of herpes labialis (cold sores).

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Action
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Rapidly converted to acyclovir. Acyclovir interferes with viral DNA synthesis. Therapeutic Effects: Inhibited viral replication, ↓ viral shedding, reduced time to healing of lesions. Reduced transmission of genital herpes.

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Adverse Reactions/Side Effects
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CNS: headache, dizziness, weakness. GI: nausea, abdominal pain, anorexia, constipation, diarrhea. Hemat: THROMBOTIC THROMBOCYTOPENIC PURPURA/HEMOLYTIC UREMIC SYNDROME (VERY HIGH DOSES IN IMMUNOSUPPRESSED PATIENTS).

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PHYSICAL THERAPY IMPLICATIONS

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Examination and Evaluation
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  • Monitor signs of thrombotic thrombocytopenic purpura (purplish spots on the skin, decreased consciousness, fatigue, weakness, shortness of breath on exertion, tachycardia) and hemolytic uremic syndrome (bloody diarrhea and vomiting, decreased urine output). Report these signs to the physician immediately.

  • Assess dizziness or weakness that might affect gait, balance, or other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

  • Assess skin and mucosal lesions to help document whether drug therapy is successful in controlling infection.

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Interventions
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  • Avoid contact with cutaneous or mucosal lesions when treating patient.

  • Always wash hands thoroughly and disinfect equipment (whirlpools, electrotherapeutic devices, treatment tables, and so forth) to help prevent the spread of infection. Use universal precautions as indicated for specific patients.

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Patient/Client-Related Instruction
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  • Advise patient to take medication as directed. Valacyclovir should not be used more frequently or longer than prescribed.

  • Remind patient that valacyclovir does not cure herpes infections. The virus lies dormant in the ganglia, and valacyclovir will not prevent the spread of infection to others.

  • Instruct patient and family/caregivers to report other troublesome side effects, including severe or prolonged headache or GI problems (nausea, diarrhea, constipation, loss of appetite, abdominal pain).

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Pharmacokinetics
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Absorption: 54% bioavailable as acyclovir after oral administration of valacyclovir.

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Distribution: CSF concentrations of acyclovir are 50% of plasma concentrations. Acyclovir crosses placenta; enters breast milk.

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Metabolism and Excretion: Rapidly converted to acyclovir via intestinal/hepatic metabolism.

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Half-life: 2.5–3.3 hr; up to 14 hr in renal impairment (acyclovir).

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TIME/ACTION PROFILE (blood levels*)

ROUTE ONSET PEAK DURATION
PO unknown 1.5–2.5 hr 8–24 hr

*Acyclovir.

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Contraindications/Precautions
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Contraindicated in: Hypersensitivity to valacyclovir or acyclovir.

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Use Cautiously in: Renal impairment (dose reduction/↑ dosing interval recommended if CCr <50 mL/min); Geri: Dose ↓ may be necessary; OB/Lactation: Pregnancy, lactation; Pedi: Children <2 yr (safety not established).

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