Therapeutic Drug Monitoring of Levoffoxacin in an Obese Adolescent: A Case Report.

Objectives: To describe the pharmacokinetics of levofloxacin in an obese adolescent patient in the pediatric intensive care unit.

Methods: A single-patient medical record review was conducted.

Results: A 168-kg, 15-year-old female with past medical history of Prader-Willi syndrome and asthma initially presented with respiratory distress secondary to asthma exacerbation. She failed non-invasive ventilation and was subsequently intubated for respiratory failure and progressed to high-frequency oscillatory ventilation. On hospital day 1 (HD 1) an infectious workup was begun because of a fever, worsening clinical status, and initiation of vasopressors and an empiric antimicrobial regimen of cefepime and clindamycin. The urine culture subsequently grew Escherichia coli and the respiratory culture grew Pseudomonas aeruginosa. She continued to be febrile, which was thought to be due to an intra-abdominal abscess. On HD 14, the antimicrobial regimen was changed to levofloxacin because of continued fevers and no significant clinical improvement. Levofloxacin was initiated at 1000 mg IV every 24 hours. Levofloxacin serum levels were obtained at 0.5, 3.5, and 11.5 hours after infusion, which were 8.61, 5.76, and 2.7 mg/L, respectively. These concentrations translated into a peak level of 8.79 mg/L, a half-life of 6.4 hours, and an AUC of 80 mg·hr/L, which are discordant from the expected peak of 16 mg/L, a half-life of 8 hours, and an AUC of 120 mg·hr/L. Based on these values, the levofloxacin regimen was adjusted to 1000 mg IV every 12 hours, and repeat levels 0.5, 3.5, and 11.5 hours after infusion were 9.91, 6.56, and 3.27 mg/L, respectively, corresponding to a peak of 10.5 mg/L, a half-life of 5.18 hours, and an AUC of 200 mg·hr/L. After the adjustment in levofloxacin regimen, she became afebrile, WBC resolution and improvement in her overall clinical status, and she received a total duration for levofloxacin of 21 days.

Conclusion: A levofloxacin regimen of 1000 mg IV every 12 hours was successful in providing for an appropriate AUC exposure and was associated with a successful clinical outcome in this morbidly obese adolescent.