VALACYCLOVIR HYDROCHLORIDE
| VALACYCLOVIR HYDROCHLORIDe (val-a-cy'clo-vir) Valtrex Classifications: antiviral; Therapeutic: antiviral Prototype: Acyclovir Pregnancy Category: B |
Availability
500 mg tablets
Action
An antiviral agent hydrolyzed in the intestinal wall or liver to acyclovir; interferes with viral DNA synthesis. Because of increased GI absorption, the plasma level of this drug is substantially higher than that of acyclovir when both are taken orally.
Therapeutic Effect
Active against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), varicella zoster virus, and cytomegalovirus. Inhibits viral replication.
Uses
Herpes zoster (shingles) in immunocompetent adults. Treatment and suppression of recurrent genital herpes; suppression of recurrent herpes in HIV-positive patients; treatment of cold sores.
Contraindications
Hypersensitivity to or intolerance of valacyclovir or acyclovir; children <2 y.
Cautious Use
Renal impairment, patients receiving nephrotoxic drugs, advanced HIV disease, allogeneic bone marrow transplant and renal transplant recipients, treatment of disseminated herpes zoster, immunocompromised patients, pregnancy (category B); lactation.
Route & Dosage
| Herpes Zoster Adult: PO 1 g (2 x 500 mg) t.i.d. for 7 d, start within 48 h of onset of zoster rash Renal Impairment Clcr 30–49 mL/min: 1 g q12h; 10–29 mL/min: 1 g q24h; <10 mL/min: 500 mg q24h Treatment of Recurrent Genital Herpes Adult: PO 500 mg b.i.d. x 3 d Renal Impairment Clcr ≤29 mL/min: 500 mg q.d. Suppression of Recurrent Genital Herpes Adult: PO 1 g q.d. Treatment of Cold Sores Adult: PO 2 g 12 h x 2 doses |
Administration
Oral- Start drug as soon as possible after diagnosis of herpes zoster, preferably within 48 h of onset of rash.
- Note: Dosage reduction is recommended for patients with renal impairment.
- Give valacyclovir after hemodialysis.
- Store at 15°–30° C (59°–86° F).
Adverse Effects (≥1%)
CNS: Headache, weakness, somnolence, dizziness, fatigue, lethargy, confusion. GI: Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, flatulence. Urogenital: Glomerulonephritis, renal tubular damage, acute renal failure. Skin: Rash, urticaria, pruritus.Interactions
Drug: Probenecid, cimetidine decrease valacyclovir elimination. Zidovudine may cause increased drowsiness and lethargy.Pharmacokinetics
Absorption: Rapidly absorbed from GI tract; 54% reaches systemic circulation as acyclovir. Peak: 1.5 h. Distribution: 13.5–17.9% bound to plasma proteins; distributes into plasma, cerebrospinal fluid, saliva, and major body organs; crosses placenta; excreted in breast milk. Metabolism: Rapidly converted to acyclovir during first pass through intestine and liver. Elimination: 40–50% in urine. Half-Life: 2.5–3.3 h.Nursing Implications
Assessment & Drug Effects
- Monitor kidney function in patients with kidney impairment or those receiving potentially nephrotoxic drugs.
- Monitor for S&S of hypersensitivity; if present, withhold drug and notify physician.
Patient & Family Education
- Be aware of potential adverse effects and do not discontinue drug until full course is completed.
- Note: Post-herpes pain is likely to be present for several months after completion of therapy.
Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; 
Canadian drug name; 
Prototype drug