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Background: Tenofovir DF (TDF) is a nucleotide reverse transcriptase inhibitor approved for the treatment of HIV-infected adults. TDF pharmacokinetics have been previously evaluated in older children after single and multiple doses using multiples of a 75-mg tablet formulation. This study evaluated the single dose pharmacokinetics of tenofovir in pediatrics using an investigational liquid formulation.

Methods: Single-dose pharmacokinetics of tenofovir were studied in HIV-infected children between 2 and 8 years of age currently receiving a stable HAART regimen. We enrolled 12 subjects and stratified them by age: ages 2 to <4 (n = 3), 4 to <6 (n = 5), and 6 to <8 years (n = 4). Each subject received a single administration of TDF oral suspension at a dose of 8 mg/kg actual body weight together with a standardized breakfast. Blood sampling was performed over 24 hours. Tenofovir was measured in serum using LC/MS/MS and pharmacokinetics parameters were calculated by noncompartmental methods.

Results: All 12 subjects (7 males, 5 females) completed the study. Median (range) age and weight were 4.7 (2.8 to 8.4) years and 18.4 (14.8 to 27.5) kg, respectively. Tenofovir pharmacokinetics were similar across the ages and age groups studied. No adverse events or notable changes in serum chemistries or hematologic parameters were observed. Tenofovir exposures approximated those observed in adults following administration of TDF 300 mg (AUC ~3000 ng h/mL, Cmax ~325 ng/mL). The terminal elimination half-life of tenofovir was slightly shorter in pediatrics versus what has been observed following single dose administration in adults (median value ~ 17 hours). Pharmacokinetics parameters follow:

*Median

Conclusions: A TDF dose of 8 mg/kg of a suspension administered to pediatric patients 2 to 8 years of age results in tenofovir exposures generally comparable to those observed in HIV-infected adults receiving 300 mg once daily.

Keywords: Tenofovir DF; Pharmacokinetics; Pediatrics