The growing resistance of Streptococcus pneumoniae to
penicillin can be overcome by increasing the dose of the
penicillin administered. This generated the recommendation that the adult dose of
amoxicillin for the treatment of acute
maxillary sinusitis (AMS) be increased from 1.5 g/day to 4.0 g/day. The objective of this study was to investigate whether the higher dose of
amoxicillin is more effective than the previously recommended dose in eradicating S. pneumoniae from the nasopharynx of patients who present with AMS. Nasopharyngeal cultures obtained from 58 patients with AMS were studied: 30 received
amoxicillin 1.5 g/day given in divided doses three times a day for 10 days (
amoxicillin/clavulanic acid 4:1 formulation) and 28 were treated with
amoxicillin 4.0 g/day given in divided doses twice a day for 10 days (
amoxicillin/clavulanic acid 16:1 formulation). Seventy-one potentially pathogenic organisms were isolated: S. pneumoniae (27 isolates), Haemophilus influenzae non-type b (25), Moraxella catarrhalis (5), Streptococcus pyogenes (5) and Staphylococcus aureus (9). The number of S. pneumoniae isolates in the 1.5 g/day group was reduced from 14 to 9 (2 intermediately resistant and 3 highly resistant). In contrast, the number of S. pneumoniae isolates in the 4.0 g/day group was reduced from 13 to 2 (1 highly resistant) (P<0.05). No differences were noted in the eradication rate of other groups of isolates, which were all susceptible to
amoxicillin/clavulanic acid. These data illustrate the superiority of 4.0 g/day
amoxicillin/clavulanic acid compared with 1.5 g/day
amoxicillin/clavulanic acid in the eradication of S. pneumoniae from the nasopharynx.