1.1 Adult Patients

Cold Sores (Herpes Labialis)

VALTREX is indicated for treatment of cold sores (herpes labialis). The efficacy of VALTREX initiated after the development of clinical signs of a cold sore (e.g., papule, vesicle, or ulcer) has not been established.

Genital Herpes

Initial Episode: VALTREX is indicated for treatment of the initial episode of genital herpes in immunocompetent adults. The efficacy of treatment with VALTREX when initiated more than 72 hours after the onset of signs and symptoms has not been established.

Recurrent Episodes: VALTREX is indicated for treatment of recurrent episodes of genital herpes in immunocompetent adults. The efficacy of treatment with VALTREX when initiated more than 24 hours after the onset of signs and symptoms has not been established.

Suppressive Therapy: VALTREX is indicated for chronic suppressive therapy of recurrent episodes of genital herpes in immunocompetent and in HIV-1−infected adults. The efficacy and safety of VALTREX for the suppression of genital herpes beyond 1 year in immunocompetent patients and beyond 6 months in HIV-1−infected patients have not been established.

Reduction of Transmission: VALTREX is indicated for the reduction of transmission of genital herpes in immunocompetent adults. The efficacy of VALTREX for the reduction of transmission of genital herpes beyond 8 months in discordant couples has not been established. The efficacy of VALTREX for the reduction of transmission of genital herpes in individuals with multiple partners and non‑heterosexual couples has not been established. Safer sex practices should be used with suppressive therapy (see current Centers for Disease Control and Prevention [CDC] Sexually Transmitted Diseases Treatment Guidelines).

Herpes Zoster

VALTREX is indicated for the treatment of herpes zoster (shingles) in immunocompetent adults. The efficacy of VALTREX when initiated more than 72 hours after the onset of rash and the efficacy and safety of VALTREX for treatment of disseminated herpes zoster have not been established.

1.2 Pediatric Patients

Cold Sores (Herpes Labialis)

VALTREX is indicated for the treatment of cold sores (herpes labialis) in pediatric patients aged greater than or equal to 12 years. The efficacy of VALTREX initiated after the development of clinical signs of a cold sore (e.g., papule, vesicle, or ulcer) has not been established.

Chickenpox

VALTREX is indicated for the treatment of chickenpox in immunocompetent pediatric patients aged 2 to less than 18 years. Based on efficacy data from clinical trials with oral acyclovir, treatment with VALTREX should be initiated within 24 hours after the onset of rash [see Clinical Studies ( 14.4)] .

1.3 Limitations of Use

The efficacy and safety of VALTREX have not been established in:

• Immunocompromised patients other than for the suppression of genital herpes in HIV‑1−infected patients with a CD4+ cell count greater than or equal to 100 cells/mm 3.
• Patients aged less than 12 years with cold sores (herpes labialis).
• Patients aged less than 2 years or greater than or equal to 18 years with chickenpox.
• Patients aged less than 18 years with genital herpes.
• Patients aged less than 18 years with herpes zoster.
• Neonates and infants as suppressive therapy following neonatal herpes simplex virus (HSV) infection.

2.1 Adult Dosing Recommendations

Cold Sores (Herpes Labialis)

The recommended dosage of VALTREX for treatment of cold sores is 2 grams twice daily for 1 day taken 12 hours apart. Therapy should be initiated at the earliest symptom of a cold sore (e.g., tingling, itching, or burning).

Genital Herpes

Initial Episode: The recommended dosage of VALTREX for treatment of initial genital herpes is 1 gram twice daily for 10 days. Therapy was most effective when administered within 48 hours of the onset of signs and symptoms.

Recurrent Episodes: The recommended dosage of VALTREX for treatment of recurrent genital herpes is 500 mg twice daily for 3 days. Initiate treatment at the first sign or symptom of an episode.

Suppressive Therapy: The recommended dosage of VALTREX for chronic suppressive therapy of recurrent genital herpes is 1 gram once daily in patients with normal immune function. In patients with a history of 9 or fewer recurrences per year, an alternative dose is 500 mg once daily.

In HIV‑1−infected patients with a CD4+ cell count greater than or equal to 100 cells/mm 3, the recommended dosage of VALTREX for chronic suppressive therapy of recurrent genital herpes is 500 mg twice daily.

Reduction of Transmission: The recommended dosage of VALTREX for reduction of transmission of genital herpes in patients with a history of 9 or fewer recurrences per year is 500 mg once daily for the source partner.

Herpes Zoster

The recommended dosage of VALTREX for treatment of herpes zoster is 1 gram 3 times daily for 7 days. Therapy should be initiated at the earliest sign or symptom of herpes zoster and is most effective when started within 48 hours of the onset of rash.

2.2 Pediatric Dosing Recommendations

Cold Sores (Herpes Labialis)

The recommended dosage of VALTREX for the treatment of cold sores in pediatric patients aged greater than or equal to 12 years is 2 grams twice daily for 1 day taken 12 hours apart. Therapy should be initiated at the earliest symptom of a cold sore (e.g., tingling, itching, or burning).

Chickenpox

The recommended dosage of VALTREX for treatment of chickenpox in immunocompetent pediatric patients aged 2 to less than 18 years is 20 mg/kg administered 3 times daily for 5 days. The total dose should not exceed 1 gram 3 times daily. Therapy should be initiated at the earliest sign or symptom [see Use in Specific Populations ( 8.4), Clinical Pharmacology ( 12.3), Clinical Studies ( 14.4)] .

2.3 Extemporaneous Preparation of Oral Suspension

Ingredients and Preparation per USP‑NF

VALTREX tablets 500 mg, cherry flavor, and Suspension Structured Vehicle USP-NF (SSV). Valacyclovir oral suspension (25 mg/mL or 50 mg/mL) should be prepared in lots of 100 mL.

Instructions for Preparing Suspension at Time of Dispensing

• Prepare SSV according to the USP-NF.
• Using a pestle and mortar, grind the required number of VALTREX 500-mg tablets until a fine powder is produced (5 VALTREX tablets for 25-mg/mL suspension; 10 VALTREX tablets for 50-mg/mL suspension).
• Gradually add approximately 5-mL aliquots of SSV to the mortar and triturate the powder until a paste has been produced. Ensure that the powder has been adequately wetted.
• Continue to add approximately 5-mL aliquots of SSV to the mortar, mixing thoroughly between additions, until a concentrated suspension is produced, to a minimum total quantity of 20 mL SSV and a maximum total quantity of 40 mL SSV for both the 25-mg/mL and 50-mg/mL suspensions.
• Transfer the mixture to a suitable 100-mL measuring flask.
• Transfer the cherry flavor* to the mortar and dissolve in approximately 5 mL of SSV. Once dissolved, add to the measuring flask.
• Rinse the mortar at least 3 times with approximately 5-mL aliquots of SSV, transferring the rinsing to the measuring flask between additions.
• Make the suspension to volume (100 mL) with SSV and shake thoroughly to mix.
• Transfer the suspension to an amber glass medicine bottle with a child-resistant closure.
• The prepared suspension should be labeled with the following information “Shake well before using. Store suspension between 2° to 8°C (36° to 46°F) in a refrigerator. Discard after 28 days.”

*The amount of cherry flavor added is as instructed by the suppliers of the cherry flavor.

2.4 Patients with Renal Impairment

Dosage recommendations for adult patients with reduced renal function are provided in Table 1  [see Use in Specific Populations ( 8.5, 8.6), Clinical Pharmacology ( 12.3)] . Data are not available for the use of VALTREX in pediatric patients with a creatinine clearance less than 50 mL/min/1.73 m 2.

Hemodialysis

Patients requiring hemodialysis should receive the recommended dose of VALTREX after hemodialysis. During hemodialysis, the half-life of acyclovir after administration of VALTREX is approximately 4 hours. About one-third of acyclovir in the body is removed by dialysis during a 4-hour hemodialysis session.

Peritoneal Dialysis

There is no information specific to administration of VALTREX in patients receiving peritoneal dialysis. The effect of chronic ambulatory peritoneal dialysis (CAPD) and continuous arteriovenous hemofiltration/dialysis (CAVHD) on acyclovir pharmacokinetics has been studied. The removal of acyclovir after CAPD and CAVHD is less pronounced than with hemodialysis, and the pharmacokinetic parameters closely resemble those observed in patients with end-stage renal disease (ESRD) not receiving hemodialysis. Therefore, supplemental doses of VALTREX should not be required following CAPD or CAVHD.

5.1 Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome (TTP/HUS)

TTP/HUS, in some cases resulting in death, has occurred in patients with advanced HIV-1 disease and also in allogeneic bone marrow transplant and renal transplant recipients participating in clinical trials of VALTREX at doses of 8 grams per day. Treatment with VALTREX should be stopped immediately if clinical signs, symptoms, and laboratory abnormalities consistent with TTP/HUS occur.

5.2 Acute Renal Failure

Cases of acute renal failure have been reported in:

• Elderly patients with or without reduced renal function. Caution should be exercised when administering VALTREX to geriatric patients, and dosage reduction is recommended for those with impaired renal function [see Dosage and Administration ( 2.4), Use in Specific Populations ( 8.5)].
• Patients with underlying renal disease who received higher-than-recommended doses of VALTREX for their level of renal function. Dosage reduction is recommended when administering VALTREX to patients with renal impairment [see Dosage and Administration ( 2.4), Use in Specific Populations ( 8.6)].
• Patients receiving other nephrotoxic drugs. Caution should be exercised when administering VALTREX to patients receiving potentially nephrotoxic drugs.
• Patients without adequate hydration. Precipitation of acyclovir in renal tubules may occur when the solubility (2.5 mg/mL) is exceeded in the intratubular fluid. Adequate hydration should be maintained for all patients.

In the event of acute renal failure and anuria, the patient may benefit from hemodialysis until renal function is restored [see Dosage and Administration ( 2.4), Adverse Reactions ( 6.3)] .

5.3 Central Nervous System Effects

Central nervous system adverse reactions, including agitation, hallucinations, confusion, delirium, seizures, and encephalopathy, have been reported in both adult and pediatric patients with or without reduced renal function and in patients with underlying renal disease who received higher-than-recommended doses of VALTREX for their level of renal function. Elderly patients are more likely to have central nervous system adverse reactions. VALTREX should be discontinued if central nervous system adverse reactions occur [see Adverse Reactions ( 6.3), Use in Specific Populations ( 8.5, 8.6)].

6.1 Clinical Trials Experience in Adult Subjects

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Cold Sores (Herpes Labialis)

In clinical trials for the treatment of cold sores, the adverse reactions reported by subjects receiving VALTREX 2 grams twice daily (n = 609) or placebo (n = 609) for 1 day, respectively, included headache (14%, 10%) and dizziness (2%, 1%). The frequencies of abnormal ALT (greater than 2 x ULN) were 1.8% for subjects receiving VALTREX compared with 0.8% for placebo. Other laboratory abnormalities (hemoglobin, white blood cells, alkaline phosphatase, and serum creatinine) occurred with similar frequencies in the 2 groups.

Genital Herpes

Initial Episode: In a clinical trial for the treatment of initial episodes of genital herpes, the adverse reactions reported by greater than or equal to 5% of subjects receiving VALTREX 1 gram twice daily for 10 days (n = 318) or oral acyclovir 200 mg 5 times daily for 10 days (n = 318), respectively, included headache (13%, 10%) and nausea (6%, 6%). For the incidence of laboratory abnormalities see Table 2.

Recurrent Episodes: In 3 clinical trials for the episodic treatment of recurrent genital herpes, the adverse reactions reported by greater than or equal to 5% of subjects receiving VALTREX 500 mg twice daily for 3 days (n = 402), VALTREX 500 mg twice daily for 5 days (n = 1,136), or placebo (n = 259), respectively, included headache (16%, 11%, 14%) and nausea (5%, 4%, 5%). For the incidence of laboratory abnormalities see Table 2.

Suppressive Therapy: Suppression of Recurrent Genital Herpes in Immunocompetent Adults: In a clinical trial for the suppression of recurrent genital herpes infections, the adverse reactions reported by subjects receiving VALTREX 1 gram once daily (n = 269), VALTREX 500 mg once daily (n = 266), or placebo (n = 134), respectively, included headache (35%, 38%, 34%), nausea (11%, 11%, 8%), abdominal pain (11%, 9%, 6%), dysmenorrhea (8%, 5%, 4%), depression (7%, 5%, 5%), arthralgia (6%, 5%, 4%), vomiting (3%, 3%, 2%), and dizziness (4%, 2%, 1%). For the incidence of laboratory abnormalities see Table 2.

            Suppression of Recurrent Genital Herpes in HIV-1-Infected Subjects: In HIV-1-infected subjects, frequently reported adverse reactions for VALTREX (500 mg twice daily; n = 194, median days on therapy = 172) and placebo (n = 99, median days on therapy = 59), respectively, included headache (13%, 8%), fatigue (8%, 5%), and rash (8%, 1%). Post-randomization laboratory abnormalities that were reported more frequently in valacyclovir subjects versus placebo included elevated alkaline phosphatase (4%, 2%), elevated ALT (14%, 10%), elevated AST (16%, 11%), decreased neutrophil counts (18%, 10%), and decreased platelet counts (3%, 0%), respectively.

Reduction of Transmission: In a clinical trial for the reduction of transmission of genital herpes, the adverse reactions reported by subjects receiving VALTREX 500 mg once daily (n = 743) or placebo once daily (n = 741), respectively, included headache (29%, 26%), nasopharyngitis (16%, 15%), and upper respiratory tract infection (9%, 10%).

Herpes Zoster

In 2 clinical trials for the treatment of herpes zoster, the adverse reactions reported by subjects receiving VALTREX 1 gram 3 times daily for 7 to 14 days (n = 967) or placebo (n = 195), respectively, included nausea (15%, 8%), headache (14%, 12%), vomiting (6%, 3%), dizziness (3%, 2%), and abdominal pain (3%, 2%). For the incidence of laboratory abnormalities see Table 2.

6.2 Clinical Trials Experience in Pediatric Subjects

The safety profile of VALTREX has been studied in 177 pediatric subjects aged 1 month to less than 18 years. Sixty-five of these pediatric subjects, aged 12 to less than 18 years, received oral tablets for 1 to 2 days for treatment of cold sores. The remaining 112 pediatric subjects, aged 1 month to less than 12 years, participated in 3 pharmacokinetic and safety trials and received valacyclovir oral suspension. Fifty-one of these 112 pediatric subjects received oral suspension for 3 to 6 days. The frequency, intensity, and nature of clinical adverse reactions and laboratory abnormalities were similar to those seen in adults.

Pediatric Subjects Aged 12 to Less than 18 Years (Cold Sores)

In clinical trials for the treatment of cold sores, the adverse reactions reported by adolescent subjects receiving VALTREX 2 grams twice daily for 1 day, or VALTREX 2 grams twice daily for 1 day followed by 1 gram twice daily for 1 day (n = 65, across both dosing groups), or placebo (n = 30), respectively, included headache (17%, 3%) and nausea (8%, 0%).

Pediatric Subjects Aged 1 Month to Less than 12 Years

Adverse events reported in more than 1 subject across the 3 pharmacokinetic and safety trials in children aged 1 month to less than 12 years were diarrhea (5%), pyrexia (4%), dehydration (2%), herpes simplex (2%), and rhinorrhea (2%). No clinically meaningful changes in laboratory values were observed.

6.3 Postmarketing Experience

In addition to adverse events reported from clinical trials, the following events have been identified during postmarketing use of VALTREX. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to VALTREX.

General

Facial edema, hypertension, tachycardia.

Allergic

Acute hypersensitivity reactions including anaphylaxis, angioedema, dyspnea, pruritus, rash, and urticaria [see Contraindications ( 4)] .

Central Nervous System ( CNS) Symptoms

Aggressive behavior; agitation; ataxia; coma; confusion; decreased consciousness; dysarthria; encephalopathy; mania; and psychosis, including auditory and visual hallucinations, seizures, tremors [see Warnings and Precautions ( 5.3), Use in Specific Populations ( 8.5, 8.6)] .

Eye

Visual abnormalities.

Gastrointestinal

Diarrhea.

Hepatobiliary Tract and Pancreas

Liver enzyme abnormalities, hepatitis.

Renal

Renal failure, renal pain (may be associated with renal failure) [see Warnings and Precautions ( 5.2), Use in Specific Populations ( 8.5, 8.6)] .

Hematologic

Thrombocytopenia, aplastic anemia, leukocytoclastic vasculitis, TTP/HUS [see Warnings and Precautions ( 5.1)] .

Skin

Erythema multiforme, rashes including photosensitivity, alopecia.

8.1 Pregnancy

Risk Summary

Clinical data over several decades with valacyclovir and its metabolite, acyclovir, in pregnant women, have not identified a drug associated risk of major birth defects. There are insufficient data on the use of valacyclovir regarding miscarriage or adverse maternal or fetal outcomes (see Data). There are risks to the fetus associated with untreated herpes simplex during pregnancy (see Clinical Considerations).

In animal reproduction studies, no evidence of adverse developmental outcomes was observed with valacyclovir when administered to pregnant rats and rabbits at system exposures (AUC) 4 (rats) and 7 (rabbits) times the human exposure at the maximum recommended human dose (MRHD) (see Data).

The estimated background risk of major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

8.2 Lactation

Risk Summary

Although there is no information on the presence of valacyclovir in human milk, its metabolite, acyclovir, is present in human milk following oral administration of valacyclovir. Based on published data, a 500-mg maternal dose of VALTREX twice daily would provide a breastfed child with an oral acyclovir dosage of approximately 0.6 mg/kg/day (see Data). There is no data on the effects of valacyclovir or acyclovir on the breastfed child or on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for VALTREX and any potential adverse effects on the breastfed child from VALTREX or from the underlying maternal condition.

Data

Following oral administration of a 500-mg dose of VALTREX to 5 lactating women, peak acyclovir concentrations (C max) in breast milk ranged from 0.5 to 2.3 times (median 1.4) the corresponding maternal acyclovir serum concentrations. The acyclovir breast milk AUC ranged from 1.4 to 2.6 times (median 2.2) maternal serum AUC. A 500-mg maternal dose of VALTREX twice daily would provide a breastfed child with an oral acyclovir dosage of approximately 0.6 mg/kg/day. Unchanged valacyclovir was not detected in maternal serum, breast milk or infant urine.

8.4 Pediatric Use

VALTREX is indicated for treatment of cold sores in pediatric patients aged greater than or equal to 12 years and for treatment of chickenpox in pediatric patients aged 2 to less than 18 years [see Indications and Usage ( 1.2), Dosage and Administration ( 2.2)] .

The use of VALTREX for treatment of cold sores is based on 2 double‑blind, placebo‑controlled clinical trials in healthy adults and adolescents (aged greater than or equal to 12 years) with a history of recurrent cold sores [see Clinical Studies ( 14.1)] .

The use of VALTREX for treatment of chickenpox in pediatric patients aged 2 to less than 18 years is based on single‑dose pharmacokinetic and multiple‑dose safety data from an open‑label trial with valacyclovir and supported by efficacy and safety data from 3 randomized, double‑blind, placebo‑controlled trials evaluating oral acyclovir in pediatric subjects with chickenpox [see Dosage and Administration ( 2.2), Adverse Reactions ( 6.2), Clinical Pharmacology ( 12.3), Clinical Studies ( 14.4)] .

The efficacy and safety of valacyclovir have not been established in pediatric patients:

• aged less than 12 years with cold sores
• aged less than 18 years with genital herpes
• aged less than 18 years with herpes zoster
• aged less than 2 years with chickenpox
• for suppressive therapy following neonatal HSV infection.

The pharmacokinetic profile and safety of valacyclovir oral suspension in children aged less than 12 years were studied in 3 open‑label trials. No efficacy evaluations were conducted in any of the 3 trials.

Trial 1 was a single‑dose pharmacokinetic, multiple‑dose safety trial in 27 pediatric subjects aged 1 to less than 12 years with clinically suspected varicella‑zoster virus (VZV) infection [see Dosage and Administration ( 2.2), Adverse Reactions ( 6.2), Clinical Pharmacology ( 12.3), Clinical Studies ( 14.4)] .

Trial 2 was a single‑dose pharmacokinetic and safety trial in pediatric subjects aged 1 month to less than 6 years who had an active herpes virus infection or who were at risk for herpes virus infection. Fifty‑seven subjects were enrolled and received a single dose of 25 mg/kg valacyclovir oral suspension. In infants and children aged 3 months to less than 6 years, this dose provided comparable systemic acyclovir exposures to that from a 1‑gram dose of valacyclovir in adults (historical data). In infants aged 1 month to less than 3 months, mean acyclovir exposures resulting from a 25‑mg/kg dose were higher (C max: ↑30%, AUC: ↑60%) than acyclovir exposures following a 1‑gram dose of valacyclovir in adults. Acyclovir is not approved for suppressive therapy in infants and children following neonatal HSV infections; therefore, valacyclovir is not recommended for this indication because efficacy cannot be extrapolated from acyclovir.

Trial 3 was a single‑dose pharmacokinetic, multiple‑dose safety trial in 28 pediatric subjects aged 1 to less than 12 years with clinically suspected HSV infection. None of the subjects enrolled in this trial had genital herpes. Each subject was dosed with valacyclovir oral suspension 10 mg/kg twice daily for 3 to 5 days. Acyclovir systemic exposures in pediatric subjects following valacyclovir oral suspension were compared with historical acyclovir systemic exposures in immunocompetent adults receiving the solid oral dosage form of valacyclovir or acyclovir for the treatment of recurrent genital herpes. The mean projected daily acyclovir systemic exposures in pediatric subjects across all age‑groups (1 to less than 12 years) were lower (C max: ↓20%, AUC: ↓33%) compared with the acyclovir systemic exposures in adults receiving valacyclovir 500 mg twice daily but were higher (daily AUC: ↑16%) than systemic exposures in adults receiving acyclovir 200 mg 5 times daily. Insufficient data are available to support valacyclovir for the treatment of recurrent genital herpes in this age‑group because clinical information on recurrent genital herpes in young children is limited; therefore, extrapolating efficacy data from adults to this population is not possible. Moreover, valacyclovir has not been studied in children aged 1 to less than 12 years with recurrent genital herpes.

8.5 Geriatric Use

Of the total number of subjects in clinical trials of VALTREX, 906 were 65 and over, and 352 were 75 and over. In a clinical trial of herpes zoster, the duration of pain after healing (post-herpetic neuralgia) was longer in subjects 65 and older compared with younger adults. Elderly patients are more likely to have reduced renal function and require dose reduction. Elderly patients are also more likely to have renal or CNS adverse events [see Dosage and Administration ( 2.4), Warnings and Precautions ( 5.2, 5.3), Clinical Pharmacology ( 12.3)] .

8.6 Renal Impairment

Dosage reduction is recommended when administering VALTREX to patients with renal impairment [see Dosage and Administration ( 2.4), Warnings and Precautions ( 5.2, 5.3)].

12.1 Mechanism of Action

Valacyclovir is an antiviral drug active against α-herpes viruses [see Microbiology ( 12.4)].

12.3 Pharmacokinetics

The pharmacokinetics of valacyclovir and acyclovir after oral administration of VALTREX have been investigated in 14 volunteer trials involving 283 adults and in 3 trials involving 112 pediatric subjects aged 1 month to less than 12 years.

Pharmacokinetics in Adults

Absorption and Bioavailability: After oral administration, valacyclovir hydrochloride is rapidly absorbed from the gastrointestinal tract and nearly completely converted to acyclovir and L-valine by first-pass intestinal and/or hepatic metabolism.

The absolute bioavailability of acyclovir after administration of VALTREX is 54.5% ± 9.1% as determined following a 1-gram oral dose of VALTREX and a 350-mg intravenous acyclovir dose to 12 healthy volunteers. Acyclovir bioavailability from the administration of VALTREX is not altered by administration with food (30 minutes after an 873 Kcal breakfast, which included 51 grams of fat).

Acyclovir pharmacokinetic parameter estimates following administration of VALTREX to healthy adult volunteers are presented in Table 3. There was a less than dose-proportional increase in acyclovir maximum concentration (C max) and area under the acyclovir concentration-time curve (AUC) after single-dose and multiple-dose administration (4 times daily) of VALTREX from doses between 250 mg to 1 gram.

There is no accumulation of acyclovir after the administration of valacyclovir at the recommended dosage regimens in adults with normal renal function.

Distribution: The binding of valacyclovir to human plasma proteins ranges from 13.5% to 17.9%. The binding of acyclovir to human plasma proteins ranges from 9% to 33%.

Metabolism: Valacyclovir is converted to acyclovir and L-valine by first-pass intestinal and/or hepatic metabolism. Acyclovir is converted to a small extent to inactive metabolites by aldehyde oxidase and by alcohol and aldehyde dehydrogenase. Neither valacyclovir nor acyclovir is metabolized by cytochrome P450 enzymes. Plasma concentrations of unconverted valacyclovir are low and transient, generally becoming non-quantifiable by 3 hours after administration. Peak plasma valacyclovir concentrations are generally less than 0.5 mcg/mL at all doses. After single-dose administration of 1 gram of VALTREX, average plasma valacyclovir concentrations observed were 0.5, 0.4, and 0.8 mcg/mL in subjects with hepatic dysfunction, renal insufficiency, and in healthy subjects who received concomitant cimetidine and probenecid, respectively.

Elimination: The pharmacokinetic disposition of acyclovir delivered by valacyclovir is consistent with previous experience from intravenous and oral acyclovir. Following the oral administration of a single 1-gram dose of radiolabeled valacyclovir to 4 healthy subjects, 46% and 47% of administered radioactivity was recovered in urine and feces, respectively, over 96 hours. Acyclovir accounted for 89% of the radioactivity excreted in the urine. Renal clearance of acyclovir following the administration of a single 1-gram dose of VALTREX to 12 healthy subjects was approximately 255 ± 86 mL/min which represents 42% of total acyclovir apparent plasma clearance.

The plasma elimination half‑life of acyclovir typically averaged 2.5 to 3.3 hours in all trials of VALTREX in subjects with normal renal function.

Specific Populations

Patients with Renal Impairment: Reduction in dosage is recommended in patients with renal impairment [see Dosage and Administration ( 2.4), Use in Specific Populations ( 8.5, 8.6)].

Following administration of VALTREX to subjects with ESRD, the average acyclovir half‑life is approximately 14 hours. During hemodialysis, the acyclovir half‑life is approximately 4 hours. Approximately one‑third of acyclovir in the body is removed by dialysis during a 4‑hour hemodialysis session. Apparent plasma clearance of acyclovir in subjects on dialysis was 86.3 ± 21.3 mL/min/1.73 m 2 compared with 679.16 ± 162.76 mL/min/1.73 m 2 in healthy subjects.

Patients with Hepatic Impairment: Administration of VALTREX to subjects with moderate (biopsy‑proven cirrhosis) or severe (with and without ascites and biopsy-proven cirrhosis) liver disease indicated that the rate but not the extent of conversion of valacyclovir to acyclovir is reduced, and the acyclovir half‑life is not affected. Dosage modification is not recommended for patients with cirrhosis.

Patients with HIV-1 Disease: In 9 subjects with HIV-1 disease and CD4+ cell counts less than 150 cells/mm 3 who received VALTREX at a dosage of 1 gram 4 times daily for 30 days, the pharmacokinetics of valacyclovir and acyclovir were not different from that observed in healthy subjects.

Geriatric Patients: After single-dose administration of 1 gram of VALTREX in healthy geriatric subjects, the half‑life of acyclovir was 3.11 ± 0.51 hours compared with 2.91 ± 0.63 hours in healthy younger adult subjects. The pharmacokinetics of acyclovir following single- and multiple‑dose oral administration of VALTREX in geriatric subjects varied with renal function. Dose reduction may be required in geriatric patients, depending on the underlying renal status of the patient [see Dosage and Administration ( 2.4), Use in Specific Populations ( 8.5, 8.6)] .

Pediatric Patients: Acyclovir pharmacokinetics have been evaluated in a total of 98 pediatric subjects (aged 1 month to less than 12 years) following administration of the first dose of an extemporaneous oral suspension of valacyclovir [see Adverse Reactions ( 6.2), Use in Specific Populations ( 8.4)] . Acyclovir pharmacokinetic parameter estimates following a 20‑mg/kg dose are provided in Table 4.

Drug Interaction Studies

When VALTREX is coadministered with antacids, cimetidine and/or probenecid, digoxin, or thiazide diuretics in patients with normal renal function, the effects are not considered to be of clinical significance (see below). Therefore, when VALTREX is coadministered with these drugs in patients with normal renal function, no dosage adjustment is recommended.

Antacids: The pharmacokinetics of acyclovir after a single dose of VALTREX (1 gram) were unchanged by coadministration of a single dose of antacids (Al 3+ or Mg ++).

Cimetidine: Acyclovir C max and AUC following a single dose of VALTREX (1 gram) increased by 8% and 32%, respectively, after a single dose of cimetidine (800 mg).

Cimetidine plus Probenecid: Acyclovir C max and AUC following a single dose of VALTREX (1 gram) increased by 30% and 78%, respectively, after a combination of cimetidine and probenecid, primarily due to a reduction in renal clearance of acyclovir.

Digoxin: The pharmacokinetics of digoxin were not affected by coadministration of VALTREX 1 gram 3 times daily, and the pharmacokinetics of acyclovir after a single dose of VALTREX (1 gram) was unchanged by coadministration of digoxin (2 doses of 0.75 mg).

Probenecid: Acyclovir C max and AUC following a single dose of VALTREX (1 gram) increased by 22% and 49%, respectively, after probenecid (1 gram).

Thiazide Diuretics: The pharmacokinetics of acyclovir after a single dose of VALTREX (1 gram) were unchanged by coadministration of multiple doses of thiazide diuretics.

12.4 Microbiology

Mechanism of Action

Valacyclovir is a deoxynucleoside analogue DNA polymerase inhibitor. Valacyclovir hydrochloride is rapidly converted to acyclovir, which has demonstrated antiviral activity against HSV types 1 (HSV‑1) and 2 (HSV‑2) and VZV both in cell culture and in vivo.

Acyclovir is a synthetic purine deoxynucleoside that is phosphorylated intracellularly by the viral encoded thymidine kinase (TK; pUL23) of HSV or VZV into acyclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In biochemical assays, acyclovir triphosphate inhibits replication of α-herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase. The greater antiviral activity of acyclovir against HSV compared with VZV is due to its more efficient phosphorylation by the viral TK.

Antiviral Activity

The quantitative relationship between the cell culture susceptibility of herpesviruses to antivirals and the clinical response to therapy has not been established in humans, and virus sensitivity testing has not been standardized. Sensitivity testing results, expressed as the concentration of drug required to inhibit by 50% the growth of virus in cell culture (EC 50), vary greatly depending upon a number of factors. Using plaque‑reduction assays, the EC 50 values against herpes simplex virus isolates range from 0.09 to 60 microM (0.02 to 13.5 mcg/mL) for HSV‑1 and from 0.04 to 44 microM (0.01 to 9.9 mcg/mL) for HSV‑2. The EC 50 values for acyclovir against most laboratory strains and clinical isolates of VZV range from 0.53 to 48 microM (0.12 to 10.8 mcg/mL). Acyclovir also demonstrates activity against the Oka vaccine strain of VZV with a mean EC 50 value of 6 microM (1.35 mcg/mL).

Resistance

In Cell Culture: Acyclovir-resistant HSV-1, HSV-2, and VZV strains were isolated in cell culture. Acyclovir-resistant HSV and VZV resulted from mutations in the viral thymidine kinase (TK, pUL23) and DNA polymerase (POL; pUL30) genes. Frameshifts were commonly isolated and result in premature truncation of the HSV TK product with consequent decreased susceptibility to acyclovir. Mutations in the viral TK gene may lead to complete loss of TK activity (TK negative), reduced levels of TK activity (TK partial), or alteration in the ability of viral TK to phosphorylate the drug without an equivalent loss in the ability to phosphorylate thymidine (TK altered). In cell culture, acyclovir resistance-associated substitutions in TK of HSV-1 and HSV-2 were observed ( Table 5).

HSV-Infected Patients: Clinical HSV-1 and HSV-2 isolates obtained from patients who failed treatment for their α-herpes virus infections were evaluated for genotypic changes in the TK and POL genes and for phenotypic resistance to acyclovir ( Table 6). HSV isolates with frameshift mutations and resistance-associated substitutions in TK and POL were identified. The listing of substitutions in the HSV TK and POL leading to decreased susceptibility to acyclovir is not all inclusive and additional changes will likely be identified in HSV variants isolated from patients who fail acyclovir-containing regimens. The possibility of viral resistance to acyclovir should be considered in patients who fail to respond or experience recurrent viral shedding during therapy.

Note: Many additional pathways to acyclovir resistance likely exist.

Cross-Resistance

Cross-resistance has been observed among HSV isolates carrying frameshift mutations and resistance-associated substitutions, which confer reduced susceptibility to penciclovir (PCV), famciclovir (FCV), and foscarnet (FOS) ( Table 7).

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

The data presented below include references to the steady‑state acyclovir AUC observed in humans treated with 1 gram of VALTREX given orally 3 times a day to treat herpes zoster. Plasma drug concentrations in animal studies are expressed as multiples of human exposure to acyclovir [see Clinical Pharmacology ( 12.3)] .

Carcinogenesis

Valacyclovir was noncarcinogenic in lifetime carcinogenicity bioassays at single daily doses (gavage) of valacyclovir giving plasma acyclovir concentrations equivalent to human levels in the mouse bioassay and 1.4 to 2.3 times human levels in the rat bioassay. There was no significant difference in the incidence of tumors between treated and control animals, nor did valacyclovir shorten the latency of tumors.

Mutagenesis

Valacyclovir was tested in 5 genetic toxicity assays. An Ames assay was negative in the absence or presence of metabolic activation. Also negative were an in vitro cytogenetic study with human lymphocytes and a rat cytogenetic study.

In the mouse lymphoma assay, valacyclovir was not mutagenic in the absence of metabolic activation. In the presence of metabolic activation (76% to 88% conversion to acyclovir), valacyclovir was mutagenic.

Valacyclovir was mutagenic in a mouse micronucleus assay.

Impairment of Fertility

Valacyclovir did not impair fertility or reproduction in male or female rats at acyclovir exposures (AUC) 6 times higher than in humans given the MRHD. Testicular atrophy occurred in male rats (orally dosed for 97 days at 18 times the MRHD) and was reversible.

14.1 Cold Sores (Herpes Labialis)

Two double‑blind, placebo‑controlled clinical trials were conducted in 1,856 healthy adults and adolescents (aged greater than or equal to 12 years) with a history of recurrent cold sores. Subjects self‑initiated therapy at the earliest symptoms and prior to any signs of a cold sore. The majority of subjects initiated treatment within 2 hours of onset of symptoms. Subjects were randomized to VALTREX 2 grams twice daily on Day 1 followed by placebo on Day 2, VALTREX 2 grams twice daily on Day 1 followed by 1 gram twice daily on Day 2, or placebo on Days 1 and 2.

The mean duration of cold sore episodes was about 1 day shorter in treated subjects as compared with placebo. The 2-day regimen did not offer additional benefit over the 1-day regimen.

No significant difference was observed between subjects receiving VALTREX or placebo in the prevention of progression of cold sore lesions beyond the papular stage.

14.2 Genital Herpes Infections

Initial Episode

Six hundred forty-three immunocompetent adults with first-episode genital herpes who presented within 72 hours of symptom onset were randomized in a double-blind trial to receive 10 days of VALTREX 1 gram twice daily (n = 323) or oral acyclovir 200 mg 5 times a day (n = 320). For both treatment groups the median time to lesion healing was 9 days, the median time to cessation of pain was 5 days, and the median time to cessation of viral shedding was 3 days.

Recurrent Episodes

Three double-blind trials (2 of them placebo-controlled) in immunocompetent adults with recurrent genital herpes were conducted. Subjects self-initiated therapy within 24 hours of the first sign or symptom of a recurrent genital herpes episode.

In 1 trial, subjects were randomized to receive 5 days of treatment with either VALTREX 500 mg twice daily (n = 360) or placebo (n = 259). The median time to lesion healing was 4 days in the group receiving VALTREX 500 mg versus 6 days in the placebo group, and the median time to cessation of viral shedding in subjects with at least 1 positive culture (42% of the overall trial population) was 2 days in the group receiving VALTREX 500 mg versus 4 days in the placebo group. The median time to cessation of pain was 3 days in the group receiving VALTREX 500 mg versus 4 days in the placebo group. Results supporting efficacy were replicated in a second trial.

In a third trial, subjects were randomized to receive VALTREX 500 mg twice daily for 5 days (n = 398) or VALTREX 500 mg twice daily for 3 days (and matching placebo twice daily for 2 additional days) (n = 402). The median time to lesion healing was about 4½ days in both treatment groups. The median time to cessation of pain was about 3 days in both treatment groups.

Suppressive Therapy

Two clinical trials were conducted, one in immunocompetent adults and one in HIV-1-infected adults.

A double‑blind, 12‑month, placebo‑ and active‑controlled trial enrolled immunocompetent adults with a history of 6 or more recurrences per year. Outcomes for the overall trial population are shown in Table 8.

Subjects with 9 or fewer recurrences per year showed comparable results with VALTREX 500 mg once daily.

In a second trial, 293 HIV‑1−infected adults on stable antiretroviral therapy with a history of 4 or more recurrences of ano‑genital herpes per year were randomized to receive either VALTREX 500 mg twice daily (n = 194) or matching placebo (n = 99) for 6 months. The median duration of recurrent genital herpes in enrolled subjects was 8 years, and the median number of recurrences in the year prior to enrollment was 5. Overall, the median pretrial HIV‑1 RNA was 2.6 log 10 copies/mL. Among subjects who received VALTREX, the pretrial median CD4+ cell count was 336 cells/mm 3; 11% had less than 100 cells/mm 3, 16% had 100 to 199 cells/mm 3, 42% had 200 to 499 cells/mm 3, and 31% had greater than or equal to 500 cells/mm 3. Outcomes for the overall trial population are shown in Table 9.

Reduction of Transmission of Genital Herpes

A double‑blind, placebo‑controlled trial to assess transmission of genital herpes was conducted in 1,484 monogamous, heterosexual, immunocompetent adult couples. The couples were discordant for HSV‑2 infection. The source partner had a history of 9 or fewer genital herpes episodes per year. Both partners were counseled on safer sex practices and were advised to use condoms throughout the trial period. Source partners were randomized to treatment with either VALTREX 500 mg once daily or placebo once daily for 8 months. The primary efficacy endpoint was symptomatic acquisition of HSV‑2 in susceptible partners. Overall HSV‑2 acquisition was defined as symptomatic HSV‑2 acquisition and/or HSV‑2 seroconversion in susceptible partners. The efficacy results are summarized in Table 10.

14.3 Herpes Zoster

Two randomized, double‑blind clinical trials in immunocompetent adults with localized herpes zoster were conducted. VALTREX was compared with placebo in subjects aged less than 50 years and with oral acyclovir in subjects aged greater than 50 years. All subjects were treated within 72 hours of appearance of zoster rash. In subjects aged less than 50 years, the median time to cessation of new lesion formation was 2 days for those treated with VALTREX compared with 3 days for those treated with placebo. In subjects aged greater than 50 years, the median time to cessation of new lesions was 3 days in subjects treated with either VALTREX or oral acyclovir. In subjects aged less than 50 years, no difference was found with respect to the duration of pain after healing (post‑herpetic neuralgia) between the recipients of VALTREX and placebo. In subjects aged greater than 50 years, among the 83% who reported pain after healing (post‑herpetic neuralgia), the median duration of pain after healing (95% CI) in days was: 40 (31, 51), 43 (36, 55), and 59 (41, 77) for 7‑day VALTREX, 14‑day VALTREX, and 7‑day oral acyclovir, respectively.

14.4 Chickenpox

The use of VALTREX for treatment of chickenpox in pediatric subjects aged 2 to less than 18 years is based on single‑dose pharmacokinetic and multiple‑dose safety data from an open‑label trial with valacyclovir and supported by safety and extrapolated efficacy data from 3 randomized, double‑blind, placebo‑controlled trials evaluating oral acyclovir in pediatric subjects.

The single‑dose pharmacokinetic and multiple‑dose safety trial enrolled 27 pediatric subjects aged 1 to less than 12 years with clinically suspected VZV infection. Each subject was dosed with valacyclovir oral suspension, 20 mg/kg 3 times daily for 5 days. Acyclovir systemic exposures in pediatric subjects following valacyclovir oral suspension were compared with historical acyclovir systemic exposures in immunocompetent adults receiving the solid oral dosage form of valacyclovir or acyclovir for the treatment of herpes zoster. The mean projected daily acyclovir exposures in pediatric subjects across all age‑groups (1 to less than 12 years) were lower (C max: ↓13%, AUC: ↓30%) than the mean daily historical exposures in adults receiving valacyclovir 1 gram 3 times daily, but were higher (daily AUC: ↑50%) than the mean daily historical exposures in adults receiving acyclovir 800 mg 5 times daily. The projected daily exposures in pediatric subjects were greater (daily AUC approximately 100% greater) than the exposures seen in immunocompetent pediatric subjects receiving acyclovir 20 mg/kg 4 times daily for the treatment of chickenpox. Based on the pharmacokinetic and safety data from this trial and the safety and extrapolated efficacy data from the acyclovir trials, oral valacyclovir 20 mg/kg 3 times a day for 5 days (not to exceed 1 gram 3 times daily) is recommended for the treatment of chickenpox in pediatric patients aged 2 to less than 18 years. Because the efficacy and safety of acyclovir for the treatment of chickenpox in children aged less than 2 years have not been established, efficacy data cannot be extrapolated to support valacyclovir treatment in children aged less than 2 years with chickenpox. Valacyclovir is also not recommended for the treatment of herpes zoster in children because safety data up to 7 days’ duration are not available [see Use in Specific Populations ( 8.4)] .