Primary syphilis: when benzathine penicillin has not achieved the expected treatment response
This protocol addresses the next clinical step for primary syphilis when the standard first-line regimen has not produced the required serological or lesion-resolution outcomes — or when penicillin cannot be used.
First-line treatment — failure condition
The preceding regimen was Benzathine penicillin G (single IM dose). Escalation to this protocol is indicated when that treatment has not achieved:
A four-fold drop in the quantitative RPR (non-treponemal) titre by 6–12 months after treatment
Resolution of syphilitic lesions (chancre)
Next-step approach
The protocol specifies alternative antibiotic-based approaches for cases where penicillin is not a viable option or has not produced the expected response. Several distinct regimens are covered.
Full regimen details — drug selection, dosing, duration, and sequencing — are available in the structured protocol.
Treatment success is defined as: a four-fold drop in the quantitative RPR (non-treponemal) titre by 6–12 months after treatment, and resolution of any syphilitic lesions (chancre). Titre normalisation may take several months, particularly following treatment of re-infection.
References
- Alternative regimens:
- Procaine penicillin G 600,000 units IM OD for 10 days: 1C.
- Doxycycline 100 mg PO BD for 14 days: 1C.
- Ceftriaxone 500 mg–1 g IM or IV OD for 10 days (if no anaphylaxis to penicillin): 1C.
- Amoxycillin 500 mg PO QDS PLUS probenecid 500 mg QDS for 14 days: 1C.
- It may take a number of months for the non-treponemal titres to drop 4-fold following treatment, particularly following treatment of re-infection.
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