Classifications: antiinfective; antiviral
Prototype: Acyclovir
Pregnancy Category: B


500 mg tablets


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 Effects

Active against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), varicella zoster virus, and cytomegalovirus. Inhibits viral replication.


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.


Hypersensitivity to or intolerance of valacyclovir or acyclovir; pregnancy (category B).

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, lactation. Safety and efficacy in children are not established.

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



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.


Drug: Probenecid, cimetidine decrease valacyclovir elimination. Zidovudine may cause increased drowsiness and lethargy.


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% excreted in urine. Half-Life: 2.5–3.3 h.

Nursing Implications

Assessment & Drug Effects

Patient & Family Education

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug