Names and pronunciation
(val-a-sye′kloh-vir) Valtrex
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Drug reference
(val-a-sye′kloh-vir) Valtrex
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Func. class.: Antiviral
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Chem. class.: Synthetic purine nucleoside analog
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Do not confuse: valACYclovir/valGANciclovir Valtrex/Valcyte
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ACTION: Interferes with DNA synthesis by conversion to acyclovir, thereby causing decreased viral replication, time of lesional healing
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USES: Treatment or suppression of herpes zoster (shingles), genital herpes, herpes labialis (cold sores), varicella, varicella zoster
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CONTRAINDICATIONS: Hyper sensitivity to this product or acyclovir, valGANciclovir Precautions: Pregnancy, breastfeeding, geriatric patients, hepatic/renal disease, electrolyte imbalance, dehydration, pen ciclovir, famciclovir, ganciclovir, hyper sensitivity, varicella
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SIDE EFFECTS CNS: Tremors, lethargy, dizziness, headache, weakness, depression, hallu cinations, seizures, encephalopathy GU: Crystalluria, renal failure ENDO: Dysmenorrhea GI: Nausea, vomiting, diarrhea, abdomi nal pain, constipation, increased AST HEMA: Thrombocytopenic purpura, hemolytic uremic syndrome INTEG: Rash MISC: Dehydration V
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INTERACTIONS Increase: blood levels of valACYclovir— cimetidine, probenecid; only significant with renal disease Drug/Lab Test Increase: LFTs, creatinine Decrease: WBC, platelets
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DOSAGE AND ROUTES Herpes zoster (shingles) • Adult: PO 1 g tid × 1 wk start within 72 hr of rash onset Genital herpes (suppressive, initial) • Adult: PO 1 g bid × 10 days initially start at earliest sign or recurrence Genital herpes (recurrent episodes) • Adult: PO 500 mg bid × 3 days start at earliest sign or recurrence Genital herpes (suppressive therapy), long term • Adult: PO 1 g/day with normal im- mune function; 500 mg/day for those with ≤9 recurrences/yr; 500 mg bid for HIV- infected patients with CD4 count ≥100 Reduction of transmission • Adult: PO 500 mg/day for source partner up to 20 mo Herpes labialis • Adult/child ≥12 yr: PO 2 g bid × 1 day at first sign of lesions Varicella (chickenpox) • Adolescent and child ≥2 yr: PO 20 mg/ kg/dose tid × 5 days, max 3 g/day Renal dose • Adult: PO CCr 30-49 mL/min, 1 g q12hr (for regimens 1 g q8hr); 1 g q12hr × 1 day (herpes labialis); CCr 10-29 mL/min, 1 g q24hr (genital herpes/herpes zos- ter); 500 mg q24hr (recurrent genital herpes); CCr <10 mL/min, 500 mg q24hr (genital herpes/herpes zoster), 500 mg q24hr (recurrent genital herpes)
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Available forms: Tabs 500 mg, 1 g
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Administer: • As soon as possible (herpes labialis, genital herpes); within 24 hr of rash (varicella) • Within 72 hr of outbreak (herpes zoster), within 24 hr (chickenpox) • Without regard to food • Caps may be made into susp by pharmacy • Store at room temperature; protect from light, moisture
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Assess: • Infection: characteristics of lesions; therapy should be started at 1st sign or symptom of herpes; most effective within 72 hr of outbreak; C&S prior to product therapy; product may be taken as soon as culture is taken; repeat C&S after treat ment; determine presence of other sexu ally transmitted diseases • Thrombocytopenic purpura, hemolytic uremic syndrome; may be fatal • CNS/psychologic status: assess cogni tion, sleep patterns, mood affect • Renal studies: I&O, BUN/creatinine, GFR; hemolytic uremic syndrome (de creased output, fatigue, pallor) may occur in transplants (renal, bone marrow) or advanced HIV • Bowel pattern before, during treatment • Skin eruptions: rash • Allergies before treatment, reaction to each medication • Pregnancy/breastfeeding: use only if benefits outweigh fetal risk; cautious use in breastfeeding, excreted in breast milk
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Evaluate: • Therapeutic response: absence of itching, painful lesions; crusting and healed lesions
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CLINICAL CONSIDERATIONS
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Patient and caregiver information: • To take as prescribed; if dose is missed, to take as soon as remembered up to 2 hr before next dose; not to double dose; to take without regard to meals • That product may be taken orally be fore infection occurs; that product should be taken when itching or pain occurs, usually before eruptions • To discuss all Rx, OTC, herbal supple ments taken with health care professional • That adequate hydration is needed to prevent crystalluria • That partners need to be told that patient has herpes, they can become infected; that condoms must be worn to prevent reinfections • That product does not cure infection, just controls symptoms; that product does not prevent infection of others • To report CNS changes (tremors, weakness, lethargy, hallucinations, sei- zures) immediately • Pregnancy/breastfeeding: Identify if pregnancy is planned or suspected or if breastfeeding
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PHARMACOKINETICS Onset unknown, Peak 1.5-2.5 hr, dura tion up to 24 hr; half-life 21⁄2-31⁄2 hr; converted to acyclovir in intestine, liver, crosses placenta, enters breast milk; excreted in urine primarily as acyclovir; protein binding 13.5%-17.9%
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• Adult/child ≥12 yr: PO 2 g bid × 1 day at first sign of lesions Varicella (chickenpox)
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• Adolescent and child ≥2 yr: PO 20 mg/ kg/dose tid × 5 days, max 3 g/day Renal dose
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