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Antimicrobial Agents and Chemotherapy, July 2008, p. 2512-2520, Vol. 52, No. 7
0066-4804/08/$08.00+0 doi:10.1128/AAC.00132-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Pharmacodynamic Analysis and Clinical Trial of Amoxicillin Sprinkle Administered Once Daily for 7 Days Compared to Penicillin V Potassium Administered Four Times Daily for 10 Days in the Treatment of Tonsillopharyngitis Due to Streptococcus pyogenes in Children
M. E. Pichichero,1*
J. R. Casey,2
S. L. Block,3
R. Guttendorf,4
H. Flanner,4
D. Markowitz,4 and
S. Clausen4
Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York,1 Legacy Pediatrics, Rochester, New York,2 Kentucky Pediatric Research, Bardstown, Kentucky,3 MiddleBrook Pharmaceuticals, Inc., Germantown, Maryland4
Received 29 January 2007/ Returned for modification 31 May 2007/ Accepted 27 February 2008
An a priori pharmacokinetic/pharmacodynamic (PK/PD) target of 40% daily time above the MIC (T >MIC; based on the MIC90 of 0.06 µg/ml for Streptococcus pyogenes reported in the literature) was shown to be achievable in a phase 1 study of 23 children with a once-daily (QD) modified-release, multiparticulate formulation of amoxicillin (amoxicillin sprinkle). The daily T >MIC achieved with the QD amoxicillin sprinkle formulation was comparable to that achieved with a four-times-daily (QID) penicillin VK suspension. An investigator-blinded, randomized, parallel-group, multicenter study involving 579 children 6 months to 12 years old with acute streptococcal tonsillopharyngitis was then undertaken. Children were randomly assigned 1:1 to receive either the amoxicillin sprinkle (475 mg for ages 6 months to 4 years, 775 mg for ages 5 to 12 years) QD for 7 days or 10 mg/kg of body weight of penicillin VK QID for 10 days (up to the maximum dose of 250 mg QID). Unexpectedly, the rates of bacteriological eradication at the test of cure were 65.3% (132/202) for the amoxicillin sprinkle and 68.0% (132/194) for penicillin VK (95% confidence interval, –12.0% to 6.6%). Thus, neither antibiotic regimen met the minimum criterion of 
85% eradication ordinarily required by the U.S. FDA for first-line treatment of tonsillopharyngitis due to S. pyogenes. The results of subgroup analyses across demographic characteristics and current infection characteristics and by age/weight categories were consistent with the primary-efficacy result. The clinical cure rates for amoxicillin sprinkle and penicillin VK were 86.1% (216/251) and 91.9% (204/222), respectively (95% confidence interval, –11.6% to –0.4%). The results of a post hoc PD analysis suggested that a requirement for 60% daily T >MIC90 more accurately predicted the observed high failure rates for bacteriologic eradication with the amoxicillin sprinkle and penicillin VK suspension studied. Based on the association between longer treatment courses and maximal bacterial eradication rates reported in the literature, an alternative composite PK/PD target taking into consideration the duration of therapy, or total T >MIC, was considered and provides an alternative explanation for the observed failure rate of amoxicillin sprinkle.
* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Box 672, Rochester, NY 14642. Phone: (585) 275-1534. Fax: (585) 273-1289. E-mail: michael_pichichero{at}urmc.rochester.edu
Published ahead of print on 10 March 2008.
Antimicrobial Agents and Chemotherapy, July 2008, p. 2512-2520, Vol. 52, No. 7
0066-4804/08/$08.00+0 doi:10.1128/AAC.00132-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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