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Author: Admin | 2025-04-28
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 ssmax 0.83 mcg/mL 1.21 mcg/mL 1.61 mcg/mL C sstrough 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 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 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 tablets significantly reduced the duration of acute infection and duration of lesion healing. The duration of pain
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