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Am Fam Physician. 1999;59(6):1651

Four antibiotics—azithromycin, cefadroxil, cefixime and ceftibuten—are currently approved for once-daily administration in the treatment of group A beta-hemolytic streptococcal pharyngitis. These agents have a broad spectrum of activity and are expensive. The treatment of choice for streptococcal pharyngitis is penicillin, but it is ineffective in a once-daily regimen. Feder and associates conducted a randomized trial to determine if once-daily amoxicillin eradicates group A streptococcal pharyngitis. This regimen was compared to penicillin V given three times daily.

The 152 children in the study were between three and 18 years of age and presented with fever, tonsillar exudate, enlarged cervical lymph nodes and sore throat. Two swab specimens were obtained, one for a rapid antigen detection test and the other for a standard throat culture. Patients were randomly assigned to receive a 10-day course of either 250 mg of penicillin V three times daily or 750 mg of amoxicillin once daily. The first follow-up visit occurred within 24 hours of the initial visit.

Other follow-up visits occurred between the fourth and sixth days of therapy and between two weeks and three weeks after completing the assigned antibiotic therapy. Throat cultures were obtained at each follow-up visit. Patients receiving amoxicillin were switched to penicillin if any throat culture was positive for streptococcal organisms. Patients on penicillin who had positive throat cultures at any of the follow-up visits were given a second 10-day course of penicillin.

At the first follow-up visit, clinical response was comparable in the two treatment groups, with about 90 percent of each group clinically improved and afebrile. One patient in the penicillin group had a positive throat culture. No patient in the amoxicillin group had a positive culture.

At subsequent follow-up visits, 13 (16 percent) of the 79 patients in the amoxicillin group and 15 (21 percent) of the 73 patients in the penicillin group had positive throat cultures. In nine patients receiving amoxicillin and seven patients receiving penicillin, the organism was a a different strain of group A beta-hemolytic streptococci, and infection in these patients was considered a “new acquisition.” The remaining four patients in the amoxicillin group and the remaining eight patients in the penicillin group were considered to have treatment failure because the organism was the same as that found initially.

The authors conclude that once-daily amoxicillin in a dosage of 750 mg is as effective in the treatment of streptococcal pharyngitis as penicillin V in a dosage of 250 mg three times daily. An advantage of amoxicillin is that its absorption is not affected by food intake (unlike penicillin) and its spectrum of activity is narrower than that of the antimicrobials currently approved for once-daily administration in the treatment of streptococcal pharyngitis. If other studies corroborate the findings of this study, amoxicillin may become another option for once-daily antibiotic therapy for streptococcal pharyngitis.

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