Acyclovir - Acyclovir capsule prescribing information
INDICATIONS AND USAGE
Herpes Zoster Infections
Acyclovir capsules are indicated for the acute treatment of herpes zoster (shingles).
Genital Herpes
Acyclovir capsules are indicated for the treatment of initial episodes and the management of recurrent episodes of genital herpes.
Chickenpox
Acyclovir capsules are indicated for the treatment of chickenpox (varicella).
DOSAGE AND ADMINISTRATION
Acute Treatment of Herpes Zoster
800 mg every 4 hours orally, 5 times daily for 7 to 10 days.
Genital Herpes
Treatment of Initial Genital Herpes
200 mg every 4 hours, 5 times daily for 10 days.
Chronic Suppressive Therapy for Recurrent Disease
400 mg 2 times daily for up to 12 months, followed by re-evaluation. Alternative regimens have included doses ranging from 200 mg 3 times daily to 200 mg 5 times daily.
The frequency and severity of episodes of untreated genital herpes may change over time. After 1 year of therapy, the frequency and severity of the patient’s genital herpes infection should be reevaluated to assess the need for continuation of therapy with acyclovir capsules.
Intermittent Therapy
200 mg every 4 hours, 5 times daily for 5 days. Therapy should be initiated at the earliest sign or symptom (prodrome) of recurrence.
Treatment of Chickenpox
Children (2 years of age and older)
20 mg/kg per dose orally 4 times daily (80 mg/kg/day) for 5 days. Children over 40 kg should receive the adult dose for chickenpox.
Adults and Children over 40 kg
800 mg 4 times daily for 5 days.
Intravenous acyclovir is indicated for the treatment of varicella-zoster infections in immunocompromised patients.
When therapy is indicated, it should be initiated at the earliest sign or symptom of chickenpox. There is no information about the efficacy of therapy initiated more than 24 hours after onset of signs and symptoms.
Patients With Acute or Chronic Renal Impairment
In patients with renal impairment, the dose of acyclovir capsules should be modified as shown in Table 3:
Creatinine | Adjusted Dosage Regimen | ||
Normal Dosage Regimen | Clearance (mL/min/1.73 m 2 ) | Dose (mg) | Dosing Interval |
200 mg every 4 hours | >10 | 200 | every 4 hours, 5x daily |
0-10 | 200 | every 12 hours | |
400 mg every 12 hours | >10 0-10 | 400 200 | every 12 hours every 12 hours |
800 mg every 4 hours | >25 | 800 | every 4 hours, 5x daily |
10-25 | 800 | every 8 hours | |
0-10 | 800 | every 12 hours | |
Hemodialysis
For patients who require hemodialysis, the mean plasma half-life of acyclovir during hemodialysis is approximately 5 hours. This results in a 60% decrease in plasma concentrations following a 6-hour dialysis period. Therefore, the patient’s dosing schedule should be adjusted so that an additional dose is administered after each dialysis.
Peritoneal Dialysis
No supplemental dose appears to be necessary after adjustment of the dosing interval.
CONTRAINDICATIONS
Acyclovir capsules are contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to acyclovir, valacyclovir, or any component of the formulation (see WARNINGS and ADVERSE REACTIONS ).
ADVERSE REACTIONS
Herpes Simplex
Short-Term Administration
The most frequent adverse events reported during clinical trials of treatment of genital herpes with acyclovir 200 mg administered orally 5 times daily every 4 hours for 10 days were nausea and/or vomiting in 8 of 298 patient treatments (2.7%). Nausea and/or vomiting occurred in 2 of 287 (0.7%) patients who received placebo.
Long-Term Administration
The most frequent adverse events reported in a clinical trial for the prevention of recurrences with continuous administration of 400 mg (two 200-mg capsules) 2 times daily for 1 year in 586 patients treated with acyclovir were nausea (4.8%) and diarrhea (2.4%). The 589 control patients receiving intermittent treatment of recurrences with acyclovir for 1 year reported diarrhea (2.7%), nausea (2.4%), and headache (2.2%).
Herpes Zoster
The most frequent adverse event reported during 3 clinical trials of treatment of herpes zoster (shingles) with 800 mg of oral acyclovir 5 times daily for 7 to 10 days in 323 patients was malaise (11.5%). The 323 placebo recipients reported malaise (11.1%).
Chickenpox
The most frequent adverse event reported during 3 clinical trials of treatment of chickenpox with oral acyclovir at doses of 10 to 20 mg/kg 4 times daily for 5 to 7 days or 800 mg 4 times daily for 5 days in 495 patients was diarrhea (3.2%). The 498 patients receiving placebo reported diarrhea (2.2%).
Observed During Clinical Practice
In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of acyclovir. 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 either their seriousness, frequency of reporting, potential causal connection to acyclovir, or a combination of these factors.
General
Anaphylaxis, angioedema, fever, headache, pain, peripheral edema.
Nervous
Aggressive behavior, agitation, ataxia, coma, confusion, decreased consciousness, delirium, dizziness, dysarthria, encephalopathy, hallucinations, paresthesia, psychosis, seizure, somnolence, tremors. These symptoms may be marked, particularly in older adults or in patients with renal impairment (see PRECAUTIONS ).
Digestive
Diarrhea, gastrointestinal distress, nausea.
Hematologic and Lymphatic
Anemia, leukocytoclastic vasculitis, leukopenia, lymphadenopathy, thrombocytopenia.
Hepatobiliary Tract and Pancreas
Elevated liver function tests, hepatitis, hyperbilirubinemia, jaundice.
Musculoskeletal
Myalgia.
Skin and Subcutaneous Tissue Disorders
Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalized exanthematous pustulosis (AGEP), and drug reaction with eosinophilia and systemic symptoms (DRESS), erythema multiforme (EM), rashes including photosensitivity, alopecia, pruritus, urticaria (see CONTRAINDICATIONS and WARNINGS ).
Special Senses
Visual abnormalities.
Urogenital
Renal failure, renal pain (may be associated with renal failure), elevated blood urea nitrogen, elevated creatinine, hematuria (see WARNINGS ).
Drug Interactions
Coadministration of probenecid with intravenous acyclovir has been shown to increase the mean acyclovir half-life and the area under the concentration-time curve. Urinary excretion and renal clearance were correspondingly reduced.
DESCRIPTION
Acyclovir is a synthetic nucleoside analogue active against herpes viruses. Acyclovir capsules are a formulation for oral administration. Each capsule of acyclovir contains 200 mg of acyclovir and the inactive ingredients colloidal silicon dioxide, croscarmellose sodium, magnesium stearate and microcrystalline cellulose. The capsule shell consists of FD&C blue #1, gelatin and titanium dioxide. The capsule black imprinting ink contains the following inactive ingredients: ammonium hydroxide, black iron oxide, n-butyl, ethyl alcohol, isopropyl alcohol, potassium hydroxide, propylene glycol and shellac.
Acyclovir is a white, crystalline powder with the molecular formula C 8 H 11 N 5 O 3 and a molecular weight of 225.2. The maximum solubility in water at 37°C is 2.5 mg/mL. The pka’s of acyclovir are 2.27 and 9.25.
The chemical name of acyclovir is 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl]-6 H -purin-6-one; it has the following structural formula:
CLINICAL PHARMACOLOGY
Pharmacokinetics
The pharmacokinetics of acyclovir after oral administration have been evaluated in healthy volunteers and in immunocompromised patients with herpes simplex or varicella-zoster virus infection. Acyclovir pharmacokinetic parameters are summarized in Table 1.
Parameter | Range |
Plasma protein binding | 9% to 33% |
Plasma elimination half-life | 2.5 to 3.3 h |
Average oral bioavailability | 10% to 20%• |
•Bioavailability decreases with increasing dose.
In one multiple-dose, crossover study in healthy subjects (n = 23), it was shown that increases in plasma acyclovir concentrations were less than dose proportional with increasing dose, as shown in Table 2. The decrease in bioavailability is a function of the dose and not the dosage form.
Parameter | 200 mg | 400 mg | 800 mg |
 | 0.83 mcg/mL | 1.21 mcg/mL | 1.61 mcg/mL |
 | 0.46 mcg/mL | 0.63 mcg/mL | 0.83 mcg/mL |
There was no effect of food on the absorption of acyclovir (n = 6); therefore, acyclovir capsules may be administered with or without food.
The only known urinary metabolite is 9-[(carboxymethoxy)methyl]guanine.
Special Populations
Adults With Impaired Renal Function
The half-life and total body clearance of acyclovir are dependent on renal function. A dosage adjustment is recommended for patients with reduced renal function (see DOSAGE AND ADMINISTRATION ).
Geriatrics
Acyclovir plasma concentrations are higher in geriatric patients compared with younger adults, in part due to age-related changes in renal function. Dosage reduction may be required in geriatric patients with underlying renal impairment (see PRECAUTIONS: Geriatric Use ).
Pediatrics
In general, the pharmacokinetics of acyclovir in pediatric patients is similar to that of adults. Mean half-life after oral doses of 300 mg/m 2 and 600 mg/m 2 in pediatric patients aged 7 months to 7 years was 2.6 hours (range 1.59 to 3.74 hours).
Drug Interactions
Coadministration of probenecid with intravenous acyclovir has been shown to increase the mean acyclovir half-life and the area under the concentration-time curve. Urinary excretion and renal clearance were correspondingly reduced.
Clinical Trials
Initial Genital Herpes
Double-blind, placebo-controlled studies have demonstrated that orally administered acyclovir significantly reduced the duration of acute infection and duration of lesion healing. The duration of pain and new lesion formation was decreased in some patient groups.
Recurrent Genital Herpes
Double-blind, placebo-controlled studies in patients with frequent recurrences (6 or more episodes per year) have shown that orally administered acyclovir given daily for 4 months to 10 years prevented or reduced the frequency and/or severity of recurrences in greater than 95% of patients.
In a study of patients who received acyclovir 400 mg twice daily for 3 years, 45%, 52%, and 63% of patients remained free of recurrences in the first, second, and third years, respectively. Serial analyses of the 3-month recurrence rates for the patients showed that 71% to 87% were recurrence free in each quarter.
Herpes Zoster Infections
In a double-blind, placebo-controlled study of immunocompetent patients with localized cutaneous zoster infection, acyclovir (800 mg 5 times daily for 10 days) shortened the times to lesion scabbing, healing, and complete cessation of pain, and reduced the duration of viral shedding and the duration of new lesion formation.
In a similar double-blind, placebo-controlled study, acyclovir (800 mg 5 times daily for 7 days) shortened the times to complete lesion scabbing, healing, and cessation of pain; reduced the duration of new lesion formation; and reduced the prevalence of localized zoster-associated neurologic symptoms (paresthesia, dysesthesia, or hyperesthesia).
Treatment was begun within 72 hours of rash onset and was most effective if started within the first 48 hours.
Adults greater than 50 years of age showed greater benefit.
Chickenpox
Three randomized, double-blind, placebo-controlled trials were conducted in 993 pediatric patients aged 2 to 18 years with chickenpox. All patients were treated within 24 hours after the onset of rash. In 2 trials, acyclovir was administered at 20 mg/kg 4 times daily (up to 3,200 mg per day) for 5 days. In the third trial, doses of 10, 15, or 20 mg/kg were administered 4 times daily for 5 to 7 days. Treatment with acyclovir shortened the time to 50% healing; reduced the maximum number of lesions; reduced the median number of vesicles; decreased the median number of residual lesions on day 28; and decreased the proportion of patients with fever, anorexia, and lethargy by day 2. Treatment with acyclovir did not affect varicella-zoster virus-specific humoral or cellular immune responses at 1 month or 1 year following treatment.
HOW SUPPLIED
Acyclovir Capsules USP 200 mg are available for oral administration as hard gelatin capsules with a white opaque body and an aqua blue opaque cap. “APO 042” is imprinted on each capsule in black ink. They are supplied as follows:
Bottles of 100 (60505-0042-6)
Bottles of 500 (60505-0042-5)
Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature] and protect from moisture.
Manufactured by: Manufactured for:
Apotex Inc. Apotex Corp.
Toronto, Ontario Weston, Florida
Canada M9L 1T9 33326
Revised: November 2025
Rev. 5
