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• Concern regarding the external validity and feasibility of low dose long term amoxicillin therapy against syphilis
  Takuma Matsuda, Rie Tominaga and Kentaro Iwata
  Published on: 14 May 2023

• Published on: 14 May 2023

  Concern regarding the external validity and feasibility of low dose long term amoxicillin therapy against syphilis

  • Takuma Matsuda, physician Kita Harima Medical Center
  • Other Contributors:
    • Rie Tominaga, physician
    • Kentaro Iwata, physician

  To the editor.

  We read with interest an article by Ikeuchi et al.1 We agree with their conclusion that the relatively low dose of amoxicillin could lead to the cure of syphilis. However, we would like to raise concern that the findings might not be generalized to different populations. The majority of the patients had concurrent HIV infection, and the study setting is well known prestigious center for HIV care in Japan, with decades of HIV care in Tokyo, suggesting that the patients who participated in the study are likely to be adherent to the medications prescribed, because they are instructed thoroughly in taking antiretroviral therapy. In addition, those who did not have HIV infection in the study did not have a previous history of syphilis, and they might also be likely to be adherent to the regimen compared with those who had repeated STDs. As pointed out in the study, the recommended duration of amoxicillin therapy by Japanese STD guideline is very long (4-8 weeks), and we are not sure whether patients with syphilis in general can be adherent to this regimen. Therefore, we consider that the findings by Ikeuchi et al. may not be generalizable, particularly for those who are not very aware of the importance of adherence to the medication, or those who take the risk of STDs lightly (and have repeated STDs). Future studies with different settings and populations might clarify our concerns.

  Reference
  1. Ikeuchi K, Fukushima K, Tanaka M, Yajima K, Im...

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  To the editor.

  We read with interest an article by Ikeuchi et al.1 We agree with their conclusion that the relatively low dose of amoxicillin could lead to the cure of syphilis. However, we would like to raise concern that the findings might not be generalized to different populations. The majority of the patients had concurrent HIV infection, and the study setting is well known prestigious center for HIV care in Japan, with decades of HIV care in Tokyo, suggesting that the patients who participated in the study are likely to be adherent to the medications prescribed, because they are instructed thoroughly in taking antiretroviral therapy. In addition, those who did not have HIV infection in the study did not have a previous history of syphilis, and they might also be likely to be adherent to the regimen compared with those who had repeated STDs. As pointed out in the study, the recommended duration of amoxicillin therapy by Japanese STD guideline is very long (4-8 weeks), and we are not sure whether patients with syphilis in general can be adherent to this regimen. Therefore, we consider that the findings by Ikeuchi et al. may not be generalizable, particularly for those who are not very aware of the importance of adherence to the medication, or those who take the risk of STDs lightly (and have repeated STDs). Future studies with different settings and populations might clarify our concerns.

  Reference
  1. Ikeuchi K, Fukushima K, Tanaka M, Yajima K, Imamura A. Clinical efficacy and tolerability of 1.5 g/day oral amoxicillin therapy without probenecid for the treatment of syphilis. Sex Transm Infect 2022; 98:173–177.

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  Conflict of Interest:
  None declared.

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