An adolescent was diagnosed with primary syphilis. He has no known drug allergies. The most appropriate treatment would be:

Rationale: A. Cefoxitin is not effective against Treponema pallidum, the causative agent of syphilis. B. A single intramuscular dose of benzathine penicillin G (Bicillin LA) is the recommended treatment for primary syphilis in patients without penicillin allergy. This regimen effectively eradicates the infection and prevents progression. C. Multiple doses of cefoxitin are unnecessary and not indicated for syphilis. D. Weekly dosing for 3 weeks of benzathine penicillin G is reserved for late latent syphilis or tertiary syphilis, not primary syphilis.