Erythromycin stearate in acute maxillary sinusitis

76 patients with acute maxillary sinusitis were treated with oral erythromycin stearate (500 mg twice or 3 times a day for 10 days). The mean concentration of erythromycin in the sinus secretion after 3-5 days' treatment was 0.6 mug/ml with the lower dosage and 1.3 mug/ml with the higher. The concentration of erythromycin in the sinus secretion was, on the average, 10-20 times higher than the minimum inhibitory concentration (MIC) for group A streptococci and pneumococci, and reached MIC values for 15-30% of 100 examined strains of Haemophilus influenzae. 81% of the patients given the smaller and 94% of those given the larger dose improved or recovered. Radiological improvement was demonstrated in both groups. The infections with H. influenzae tended to respond somewhat less to the treatment than those with pneumococci. Comparisons of the roentgen findings and the findings at aspiration showed good agreement. An extra projection taken with the patient recumbent and the affected side downwards gave no information above that obtained from the routine projections. The large dose caused side effects more often (in 17/41 patients) than the smaller one (4/35 patients). In 10 patients treatment was discontinued because of side effects; 8 of them had received the larger dose.