Acyclovir

ADVERSE REACTIONS Herpes Simplex: Short-Term Administration: The most frequent adverse events reported during clinical trials of treatment of genital herpes with acyclovir 200mg 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 400mg (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 800mg 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 20mg/kg 4 times daily for 5 to 7 days or 800mg 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: Alopecia, erythema multiforme, photosensitive rash, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria. Special Senses: Visual abnormalities. Urogenital: Renal failure, renal pain (may be associated with renal failure), elevated blood urea nitrogen, elevated creatinine, hematuria (see WARNINGS ).

CONTRAINDICATIONS

DESCRIPTION Acyclovir is a synthetic nucleoside analogue active against herpesviruses. Acyclovir Tablets are formulations for oral administration. Each 800-mg tablet of acyclovir contains 800mg of acyclovir and the inactive ingredients FD&C Blue No. 2, magnesium stearate, microcrystalline cellulose, povidone, and sodium starch glycolate. Each 400-mg tablet of acyclovir contains 400mg of acyclovir and the inactive ingredients magnesium stearate, microcrystalline cellulose, povidone and sodium starch glycolate. Acyclovir is a white, crystalline powder with the molecular formula C8H11N5O3 and a molecular weight of 225. The maximum solubility in water at 37°C is 2.5mg/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: structure

DOSAGE AND ADMINISTRATION Acute Treatment of Herpes Zoster: 800mg every 4 hours orally, 5 times daily for 7 to 10 days. Genital Herpes: Treatment of Initial Genital Herpes: 200mg every 4 hours, 5 times daily for 10 days. Chronic Suppressive Therapy for Recurrent Disease: 400mg 2 times daily for up to 12 months, followed by re-evaluation. Alternative regimens have included doses ranging from 200mg 3 times daily to 200mg 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: 200mg 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): 20mg/kg per dose orally 4 times daily (80mg/kg/day) for 5 days. Children over 40kg should receive the adult dose for chickenpox. Adults and Children over 40 kg: 800mg 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 Tablets should be modified as shown in Table 3. Table 3. Dosage Modification for Renal Impairment Normal Dosage Regimen Creatinine Clearance (mL/min/1.73 m 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.

INDICATIONS AND USAGE Herpes Zoster Infections: Acyclovir is indicated for the acute treatment of herpes zoster (shingles). Genital Herpes: Acyclovir is indicated for the treatment of initial episodes and the management of recurrent episodes of genital herpes. Chickenpox: Acyclovir is indicated for the treatment of chickenpox (varicella).

WARNINGS

OVERDOSAGE

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 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. 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 bio availability 10 % to 20 % * * Bio availability decreases with increasing dose.

VIROLOGY Mechanism of Antiviral Action: Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts acyclovir into acyclovir mono phosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In vitro, acyclovir triphosphate stops replication of herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation into 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 Activities: The quantitative relationship between the in vitro susceptibility of herpes viruses 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 (IC 50 ), vary greatly depending upon a number of factors. Using plaque-reduction assays, the IC 50 against herpes simplex virus isolates ranges from 0.02 to 13.5mcg/mL for HSV-1 and from 0.01 to 9.9mcg/mL for HSV-2. The IC 50 for acyclovir against most laboratory strains and clinical isolates of VZV ranges from 0.12 to 10.8mcg/mL. Acyclovir also demonstrates activity against the Oka vaccine strain of VZV with a mean IC 50 of 1.35mcg/mL. Drug Resistance: Resistance of HSV and VZV to acyclovir can result from qualitative and quantitative changes in the viral TK and/or DNA polymerase. Clinical isolates of HSV and VZV with reduced susceptibility to acyclovir have been recovered from immunocompromised patients, especially with advanced HIV infection. While most of the acyclovir-resistant mutants isolated thus far from immunocompromised patients have been found to be TK-deficient mutants, other mutants involving the viral TK gene (TK partial and TK altered) and DNA polymerase have been isolated. TK-negative mutants may cause severe disease in infants and immunocompromised adults. The possibility of viral resistance to acyclovir should be considered in patients who show poor clinical response during therapy.

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 bio availability 10 % to 20 % * * Bio availability decreases with increasing dose.

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Acyclovir Acyclovir ACYCLOVIR ACYCLOVIR MICROCRYSTALLINE CELLULOSE POVIDONE K30 SODIUM STARCH GLYCOLATE TYPE A POTATO MAGNESIUM STEARATE FD&C BLUE NO. 2 Light Blue Caplet Shaped S042

ANDA209366

Acyclovir

Acyclovir

50090-6335

HUMAN PRESCRIPTION DRUG

ORAL

ACYCLOVIR Label Image

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 SS C max 0.83 mcg /mL 1.21 mcg /mL 1.61 mcg /mL SS C trough 0.46 mcg /mL 0.63 mcg /mL 0.83 mcg /mL

Information for Patients: Patients are instructed to consult with their physician if they experience severe or troublesome adverse reactions, they become pregnant or intend to become pregnant, they intend to breastfeed while taking orally administered acyclovir, or they have any other questions. Patients should be advised to maintain adequate hydration. Herpes Zoster: There are no data on treatment initiated more than 72 hours after onset of the zoster rash. Patients should be advised to initiate treatment as soon as possible after a diagnosis of herpes zoster. Genital Herpes Infections: Patients should be informed that acyclovir is not a cure for genital herpes. There are no data evaluating whether acyclovir will prevent transmission of infection to others. Because genital herpes is a sexually transmitted disease, patients should avoid contact with lesions or intercourse when lesions and/or symptoms are present to avoid infecting partners. Genital herpes can also be transmitted in the absence of symptoms through asymptomatic viral shedding. If medical management of a genital herpes recurrence is indicated, patients should be advised to initiate therapy at the first sign or symptom of an episode. Chickenpox: Chickenpox in otherwise healthy children is usually a self-limited disease of mild to moderate severity. Adolescents and adults tend to have more severe disease. Treatment was initiated within 24 hours of the typical chickenpox rash in the controlled studies, and there is no information regarding the effects of treatment begun later in the disease course.

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 ).

Nursing Mothers: Acyclovir concentrations have been documented in breast milk in 2 women following oral administration of acyclovir and ranged from 0.6 to 4.1 times corresponding plasma levels. These concentrations would potentially expose the nursing infant to a dose of acyclovir up to 0.3mg/kg/day. Acyclovir should be administered to a nursing mother with caution and only when indicated.

Pediatric Use: Safety and effectiveness of oral formulations of acyclovir in pediatric patients younger than 2 years of age have not been established.

Pregnancy: Teratogenic Effects: Pregnancy Category B. Acyclovir administered during organogenesis was not teratogenic in the mouse (450mg/kg/day, p.o.), rabbit (50mg/kg/day, s.c. and IV), or rat (50mg/kg/day, s.c.). These exposures resulted in plasma levels 9 and 18, 16 and 106, and 11 and 22 times, respectively, human levels. There are no adequate and well-controlled studies in pregnant women. A prospective epidemiologic registry of acyclovir use during pregnancy was established in 1984 and completed in April 1999. There were 749 pregnancies followed in women exposed to systemic acyclovir during the first trimester of pregnancy resulting in 756 outcomes. The occurrence rate of birth defects approximates that found in the general population. However, the small size of the registry is insufficient to evaluate the risk for less common defects or to permit reliable or definitive conclusions regarding the safety of acyclovir in pregnant women and their developing fetuses. Acyclovir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

HOW SUPPLIED Product: 50090-6335 NDC: 50090-6335-0 35 TABLET in a BOTTLE NDC: 50090-6335-2 70 TABLET in a BOTTLE NDC: 50090-6335-3 40 TABLET in a BOTTLE

PRECAUTIONS