In this prospective randomized clinical study a total of 59 patients of both sexes (above 18 years of age) were enrolled. Thirty patients with acute
sinusitis were randomly allocated to two treatment groups, one group receiving 1000 mg
amoxicillin every 12 h for 10 days and the other group receiving 500 mg
amoxicillin every 8 h for 10 days. The median concentration of
amoxicillin in nasal secretions was 2.34 micrograms/ml in the 12-h administration group and 1.95 micrograms/ml in the 8-h administration group. Median bioavailability of
antibiotic at 8-24 h did not show any statistical differences between the two treatment schemes [probability (Z) = 0.2]. Twenty-nine patients with chronic
sinusitis were then randomly allocated to three groups, with patients receiving 1000 mg
amoxicillin at 12, 8 or 6 h before nasal and/or sinus surgery was carried out. The mean
amoxicillin concentrations in mucosal tissues removed intraoperatively ranged from 0.69 to 0.99 microgram/g samples. Statistical evaluation by analysis of variance did not show any statistically significant differences among the three treatment groups [probability (F) = 0.1705]. In all cases of acute and chronic
sinusitis,
amoxicillin concentrations exceeded minimum inhibitory concentration values for pathogens common in
sinusitis. Our results indicate that 1000 mg
amoxicillin administered twice daily produces tissue concentrations high enough to be clinically effective in patients with either acute or chronic
sinusitis.