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How does twice-daily compare with once-daily amoxicillin for GAS pharyngitis?

A recent study demonstrated that amoxicillin, given once daily, is not inferior to amoxicillin, given twice daily, to treat group A streptococcal (GAS) pharyngitis. The study was conducted over two years in 652 children between 3 and 18 years old who visited a single pediatric practice with symptoms and signs of GAS pharyngitis, which was confirmed by rapid GAS testing.

Investigators first stratified the children into two groups by weight: less than 40 kg and 40 kg or more. (Children who weighed less than 40 kg were more likely than those of higher weight to have a rash.) Half the children in each of the weight groups then were assigned to receive amoxicillin once daily or twice daily, for 10 days. For children under 40 kg, the amoxicillin dosage was 750 mg once daily or 375 mg twice daily; for children 40 kg or more, the amoxicillin dosage was 1,000 mg once daily or 500 mg twice daily. At a second visit, 14 to 21 days after treatment was begun, and at a third visit, 28 to 35 days later, investigators determined the bacteriologic failure rate for GAS in the pharynx (by means of throat culture) and assessed subjects for clinical cure and recurrence.

At the second visit, all patients had achieved clinical cure, and the bacteriologic failure rate for evaluable patients was comparable in the two treatment groups: 20.1% for the once-daily group and 15.5% for the twice-daily group. At the third visit, rates of bacteriologic relapse and clinical recurrence were low in all patients. Patients in the twice-daily groups had a higher bacteriologic failure rate (7.1% vs 2.8% for the once-daily group), however. No risk factors for bacteriologic failure were apparent. Each treatment group had only two late clinical recurrences.

Commentary Amoxicillin has a narrow spectrum of activity, which may minimize bacterial resistance in your community. It is inexpensive, tastes good, and, with once-a-day dosing, may provide better adherence than other antibiotics do. Once-a-day amoxicillin may be worth a try for group A strep pharyngitis.