Most respiratory tract infections are caused by viruses. Bacterial respiratory tract infections are usually treated empirically with antibiotic therapy that targets the most probable causative pathogens. Recommended antibiotic regimens for outpatient treatment of some common respiratory tract infections are listed in Table 1 for adults and Table 2 for children.

The FDA has approved an extended-release formulation of amoxicillin (Moxatag – MiddleBrook) for once-daily treatment of pharyngitis or tonsillitis caused by Streptococcus pyogenes in adults and children ≥12 years old. Approval was based on an unpublished study that found once-daily treatment with Moxatag 775 mg for 10 days non-inferior to penicillin V 250 mg four times a day for 10 days in eradication of S. pyogenes.

For decades, the drug of choice for oral treatment of streptococcal pharyngitis in adolescents and adults has been penicillin V 250 mg taken three or four times a day.1 Amoxicillin is equally effective, but penicillin is generally recommended because of its narrower spectrum. In adults, immediate-release amoxicillin is usually dosed 375-500 mg two to three times a day, but giving it in a higher dose (750-1000 mg) once a day appears to be equally effective for treatment of strep throat.2-4

Each Moxatag tablet contains 775 mg of amoxicillin divided into one immediate-release and two delayedrelease components. Compared to a similar dose of immediate-release amoxicillin suspension, absorption of amoxicillin from the new formulation is slower, resulting in a lower peak serum concentration, but the elimination half-life and amoxicillin exposure (AUC) are similar. S. pyogenes is susceptible to these serum concentrations, but they may be too low to treat other types of infections.

A 10-day supply of Moxatag is expected to cost about $100 compared to $4 for a similar course of penicillin V or immediate-release amoxicillin.5 There is no good reason to prescribe Moxatag.

1. A Bisno et al. Practice guidelines for the diagnosis and management of group A streptococcal pharyngitis. Infectious Disease Society of America. Clin Infect Dis 2002; 35:113.
2. P Shvartzman et al. Treatment of streptococcal pharyngitis with amoxycillin once a day. BMJ 1993; 306:1170.
3. HM Feder Jr. et al. Once-daily therapy for streptococcal pharyngitis with amoxicillin. Pediatrics 1999; 103:47.
4. HW Clegg et al. Treatment of streptococcal pharyngitis with once-daily compared with twice-daily amoxicillin: a noninferiority trial. Pediatr Infect Dis J 2006; 25:761.
5. Retail cost at one Walgreens pharmacy. February 27, 2009.

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Cefditoren pivoxil (Spectracef — TAP), a new oral third-generation cephalosporin, has been approved by the FDA for treatment of acute exacerbations of chronic bronchitis, pharyngitis, tonsillitis and uncomplicated skin and soft tissue infections in adults and children 12 or more years old. The drug has been used in Japan for 7 years.