What is the treatment of choice for primary syphilis?

The treatment of choice for primary syphilis is an intramuscular injection of benzathine penicillin G. This is regarded as the most effective and standard treatment because it not only effectively eradicates the Treponema pallidum bacteria, which is responsible for syphilis, but also provides a long-duration effect due to the slow release from the injection site. Administering a single dose is typically sufficient for the management of primary syphilis, which presents as a painless ulcerative lesion known as a chancre.

Other antibiotics, while they may have effectiveness against different infections, are not the first-line treatments for syphilis. Doxycycline is an alternative treatment for those with penicillin allergies but is not preferred as the first line. Azithromycin was previously considered for use in treating syphilis, but issues with efficacy and resistance have led to diminished recommendations for its use. Ceftriaxone is a cephalosporin antibiotic effective against various bacterial infections, but it is not indicated for syphilis. Thus, the single dose of benzathine penicillin G stands as the most effective and well-supported treatment for primary syphilis.