Two relatively small previous studies that compared the efficacy of amoxicillin, used once or twice a day for pharyngitis caused by group A beta-hemolytic streptococcus (BHCA), showed similar bacteriological efficacy of the two regimens. A larger randomized controlled trial was conducted to confirm this data.

The study was conducted in one of the pediatric medical establishments from October to May for 2 consecutive years (2001-2003). Children 3-18 years of age with symptoms of pharyngitis caused by GBSA were included in the study. The patients underwent an express study to detect HBAS. The dose of antibiotic depended on body weight (less than 40 kg or more than 40 kg). In a random order, the children were divided into one of the treatment groups: amoxicillin once a day (750 mg or 1000 mg) or 2 times a day (2 doses of 375 mg or 500 mg) for 10 days. The frequency of bacteriological ineffectiveness was assessed by the frequency of BSA excretion from the pharynx on days 14-21 (visit 2) and 28-35 days (visit 3) after the start of treatment. To distinguish the bacteriological ineffectiveness of the new cases of infection, a typing of the isolated HBSS strains was carried out. Adverse reactions were recorded daily by patients in special files. Compliance was assessed by the amount of drug returned.

The study included 652 patients (326 in each group). The patients in the two groups were comparable in all demographic and clinical characteristics, the only characteristic being a higher frequency of rashes in children weighing less than 40 kg in the two groups. At visit 2, the frequency of ineffectiveness was 20.1% (59 of 294) with amoxicillin treatment once a day and 15.5% (46 of 296) with a prescription for antibiotics 2 times a day (4.53% difference; 90% confidence interval [CI] from -0.6 to 9.7). At visit 3, the frequency of ineffectiveness was 2.8% (6 of 216) and 7.1% (16 of 225) with therapy 1 and 2 times a day, respectively (difference -4.33 %; 90% CI from -7.7 to -1.0).

Adverse effects from the gastrointestinal tract and other systems were observed with the same frequency in both groups. Suspected allergic reactions occurred in 0.9% (6 of 635) of the patients. Adherence in the two treatment groups exceeded 95%.

Thus, with pharyngitis caused by group A beta-hemolytic streptococcus, a 10-day course of treatment with amoxicillin 1 time per day is not less effective than a 10-day course of treatment with amoxicillin medicine twice a day. When taking amoxicillin 1 time a day, adverse reactions from the gastrointestinal tract and other systems do not occur more often than when using an antibiotic 2 times a day.