Penetration of loracarbef into the maxillary sinus: a pharmacokinetic assessment

Loracarbef, a beta-lactam antibiotic of the carbacephem class, is active in vitro against pathogens associated with acute maxillary sinusitis. To study the extent and duration of maxillary sinus fluid penetration after administration of loracarbef, 20 patients (10 men, 10 women; average age, 41 +/- 13 years) with acute sinusitis were treated with loracarbef 400 mg every 12 hours for 10 days. A lavage catheter was inserted into the maxillary sinus, and 150-microL sinus fluid samples were obtained at 0 (baseline), 0.5, 1, 1.5, 2, and 2.5 hours after the first dose and at 24 and 48 hours (12 hours after the second and fourth doses, respectively). Venous blood samples were obtained at the same times. Maxillary fluid and serum samples were frozen immediately at -20 degrees C to -70 degrees C until later bioassay using a direct agar diffusion method. Excluding missing data or inappropriately timed samples, the mean (+/- SD) sinus fluid concentrations were 0.16 +/- 0.12 microgram/mL at baseline, 0.23 +/- 0.17 microgram/mL at 0.5 hour, 1.11 +/- 1.44 micrograms/mL at 1 hour, 1.63 +/- 2.07 micrograms/mL at 1.5 hours, 1.75 +/- 2.01 micrograms/mL at 2 hours, and 1.60 +/- 1.96 micrograms/mL at 2.5 hours after dose. The mean sinus fluid concentration before the third dose (approximately 12 hours after the second dose) was 1.01 +/- 0.89 microgram/mL and before the fifth dose (approximately 12 hours after the fourth dose) was 0.88 +/- 0.90 microgram/mL. Taking the highest sinus fluid concentration measured in each patient, the mean peak sinus fluid concentration was 2.12 +/- 1.98 micrograms/mL (range, 0 to 6.7 micrograms/mL). The pretherapy peripheral leukocyte count appeared to have a statistically significant association (P < 0.01) with loracarbef sinus fluid penetration as estimated by the sinus fluid area under the concentration-time curve at 0 to 2.5 hours. Loracarbef 400 mg twice daily achieved sinus fluid concentrations that appeared to exceed the minimum concentration required to inhibit 90% of relevant acute sinusitis pathogens throughout the 12-hour interdose interval in most patients with acute maxillary sinusitis.