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The following information comes from DailyMed, an FDA label information provider.

Adverse Reactions

The following serious adverse reactions are discussed in greater detail in other sections of the labeling:

The most common adverse reactions reported in at least 1 indication by >10% of adult patients treated with valacyclovir hydrochloride and observed more frequently with valacyclovir hydrochloride compared to placebo are headache, nausea, and abdominal pain. The only adverse reaction reported in >10% of pediatric patients <18 years of age was headache.

6.1 Clinical Trials Experience in Adult Patients

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 studies for the treatment of cold sores, the adverse reactions reported by patients receiving valacyclovir hydrochloride 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 (>2 x ULN) were 1.8% for patients receiving valacyclovir hydrochloride 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 study for the treatment of initial episodes of genital herpes, the adverse reactions reported by ≥5% of patients receiving valacyclovir hydrochloride 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 studies for the episodic treatment of recurrent genital herpes, the adverse reactions reported by ≥5% of patients receiving valacyclovir hydrochloride 500 mg twice daily for 3 days (n = 402), valacyclovir hydrochloride 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 study for the suppression of recurrent genital herpes infections, the adverse reactions reported by patients receiving valacyclovir hydrochloride 1 gram once daily (n = 269), valacyclovir hydrochloride 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-Infected Patients: In HIV-infected patients, frequently reported adverse reactions for valacyclovir hydrochloride (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 study for the reduction of transmission of genital herpes, the adverse reactions reported by patients receiving valacyclovir hydrochloride 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 studies for the treatment of herpes zoster, the adverse reactions reported by patients receiving valacyclovir hydrochloride 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.

a Data were not collected prospectively.LLN = Lower limit of normal.ULN = Upper limit of normal.
Laboratory AbnormalityHerpes ZosterGenital Herpes TreatmentGenital Herpes Suppression
ValacyclovirHydrochloride1 gram3 times daily(n = 967)Placebo(n = 195)ValacyclovirHydrochloride1 gramtwice daily(n = 1,194)ValacyclovirHydrochloride500 mgtwice daily(n = 1,159)Placebo(n = 439)ValacyclovirHydrochloride1 gramonce daily(n = 269)ValacyclovirHydrochloride500 mgonce daily(n = 266)Placebo(n =134)
  Hemoglobin    (<0.8 x LLN) 
   White blood cells    (<0.75 x LLN)
   Platelet count    (<100,000/mm3) 
   AST (SGOT)    (>2 x ULN) 
   Serum creatinine    (>1.5 x ULN)
0.8%

1.3%

1%

1%

0.2%
0%

0.6%

1.2%

0%

0%
0.3%

0.7%

0.3%

1%

0.7%
0.2%

0.6%

0.1%

a

0%
0%

0.2%

0.7%

0.5%

0%
0%

0.7%

0.4%

4.1%

0%
0.8%

0.8%

1.1%

3.8%

0%
0.8%

1.5%

1.5%

3%

0%

6.2 Clinical Trials Experience in Pediatric Patients

The safety profile of valacyclovir hydrochloride has been studied in 177 pediatric patients 1 month to <18 years of age. Sixty-five of these pediatric patients, 12 to <18 years of age, received oral tablets for 1 to 2 days for treatment of cold sores. The remaining 112 pediatric patients, 1 month to <12 years of age, participated in 3 pharmacokinetic and safety studies and received valacyclovir oral suspension. Fifty-one of these 112 pediatric patients 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 Patients 12 to <18 Years of Age (Cold Sores):  In clinical studies for the treatment of cold sores, the adverse reactions reported by adolescent patients receiving valacyclovir hydrochloride 2 grams twice daily for 1 day, or valacyclovir hydrochloride 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 Patients 1 Month to <12 Years of Age:  Adverse events reported in more than 1 subject across the 3 pharmacokinetic and safety studies in children 1 month to <12 years of age 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 valacyclovir hydrochloride. 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 valacyclovir hydrochloride.

General: Facial edema, hypertension, tachycardia.

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

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.

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