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 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 >10 200 every 4 hours, 5x daily 0 to 10 200 every 12 hours 400 mg every 12 hours >10 400 every 12 hours 0 to 10 200 every 12 hours 800 mg every 4 hours >25 800 every 4 hours, 5x daily 10 to 25 800 every 8 hours 0 to 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.

ily 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: 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 ).

mcg/ml 0.83 mcg/ml there was no effect of food on the absorption of acyclovir (n = 6); therefore, acyclovir tablets 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 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.