What is mechanism of action?

mechanism of action is DNA Polymerase Inhibitors [MoA]

Acyclovir

Check Coverage RestrictionsSee your patient's specific prior authorization requirements including coverage restrictions and step therapies

Or select your patient's insurance carrier from the list below:

Check Drug Interactions

Acyclovir Prescribing Information

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 re-evaluated to assess the need for continuation of therapy with acyclovir.

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.

Table 3. Dosage Modifications for Renal Impairment
Normal Dosage Regimen	Creatinine Clearance (mL/min/1.73m ²)	Adjusted Dosage Regimen Dose (mg)	Dosing Interval
200 mg every 4 hours	>10 0-10	200 200	every 4 hours, 5x daily 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 10-25 0-10	800 800 800	every 4 hours, 5x daily every 8 hours 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.

Bioequivalence of Dosage Forms:

acyclovir Suspension was shown to be bioequivalent to acyclovir Capsules (n = 20) and 1 acyclovir 800-mg capsule was shown to be bioequivalent to 4 acyclovir 200-mg capsules (n = 24).

Acyclovir is a synthetic nucleoside analogue active against herpes viruses. Acyclovir capsules are formulations for oral administration.

Each capsule contains 200 mg of acyclovir and the inactive ingredients: lactose monohydrate, sodium lauryl sulfate, sodium starch glycolate, and magnesium stearate. The capsule shell consists of FD&C Blue #1, gelatin, and titanium dioxide. The imprinting ink contains, FD&C Blue #1, FD&C Blue #2, FD&C Red #40, D&C Yellow #10, iron oxide black, pharmaceutical shellac glaze and propylene glycol.

Acyclovir is a white, crystalline powder with the molecular formula C

₈H

₁₁N

₅O

₃and a molecular weight of 225. The maximum solubility in water at 37degree 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

-purin-6-one; it has the following structural formula:

Referenced Image

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.

Table 1. Acyclovir Pharmacokinetic Characteristics (Range)
Parameter	Range
Plasma protein binding	9% to 33%
Plasma elimination half-life	2.5 to 3.3 hr
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.

Table 2. Acyclovir Peak and Trough Concentrations at Steady State
Parameter	200 mg	400 mg	800 mg
C _ss max	0.83 mcg/mL	1.21 mcg/mL	1.61 mcg/mL
C _ss trough	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 to 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

Geriatric Use:

Of 376 subjects who received acyclovir in a clinical study of herpes zoster treatment in immunocompetent subjects ≥ 50 years of age, 244 were 65 and over while 111 were 75 and over. No overall differences in effectiveness for time to cessation of new lesion formation or time to healing were reported between geriatric subjects and younger adult subjects. The duration of pain after healing was longer in patients 65 and over. Nausea, vomiting, and dizziness were reported more frequently in elderly subjects. 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. With respect to CNS adverse events observed during clinical practice, somnolence, hallucinations, confusion, and coma were reported more frequently in elderly patients (see CLINICAL PHARMACOLOGY, ADVERSE REACTIONS: Observed During Clinical Practice, and DOSAGE AND ADMINISTRATION).

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/m2 and 600 mg/m2 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.

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.

Report Adverse Event

Acyclovir

Acyclovir Prescribing Information

Acyclovir PubMed™ News