Late latent syphilis is infection acquired at least one year before presentation, or of unknown duration. When penicillin cannot be used — because of a documented allergy or because the patient declines parenteral administration — an alternative treatment strategy is required.
Syphilis is classified as late (or of undetermined duration) after at least one year from the time of infection. Penicillin remains the reference standard for this stage, but when it is contraindicated or refused, clinicians must consider alternative regimens — with the important caveat that evidence supporting their effectiveness is limited compared with penicillin.
Some specialists favour penicillin desensitization over non-penicillin regimens precisely because of this evidence gap.
An oral antibiotic course is the primary non-penicillin option in this setting. The complete regimen — including agent selection, dosing schedule, and duration — is detailed in the full structured protocol.
DOI: 10.1111/jdv.16946
Rather arbitrarily classified as early if within the first year of infection and late (or undetermined duration) after ≥1 year.
Penicillin allergy or parenteral treatment refused: some specialists recommend penicillin desensitization because the evidence base for the effectiveness of non-penicillin regimens is weak.
Doxycycline 200 mg daily (either 100 mg twice daily or as a single 200 mg dose) orally for 21–28 days.
Some specialists recommend penicillin desensitization because the evidence base for the effectiveness of non-penicillin regimens is weak.
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