What is the treatment for a painful chancre on the penis, likely caused by syphilis?

Treatment of Painful Penile Chancre

A painful penile chancre is most likely chancroid (caused by Haemophilus ducreyi), not syphilis, and should be treated with either azithromycin 1 g orally as a single dose, ceftriaxone 250 mg IM as a single dose, or erythromycin base 500 mg orally four times daily for 7 days. 1

Critical Diagnostic Distinction

The key clinical feature here is pain—this fundamentally changes the differential diagnosis:

• Chancroid presents with painful ulcers with tender inguinal lymphadenopathy in one-third of patients, and when accompanied by suppurative adenopathy is almost pathognomonic 1
• Syphilitic chancres are characteristically painless 2, 3
• The combination of a painful ulcer with tender inguinal adenopathy is highly suggestive of chancroid rather than syphilis 1

Recommended Treatment Regimens for Chancroid

All three regimens below are equally effective and cure infection, resolve symptoms, and prevent transmission 1:

• Azithromycin 1 g orally in a single dose (preferred for compliance) 1
• Ceftriaxone 250 mg IM in a single dose (preferred for compliance) 1
• Erythromycin base 500 mg orally four times daily for 7 days 1

Azithromycin and ceftriaxone offer superior adherence due to single-dose administration, and no antimicrobial resistance has been reported to these agents 1, 4.

Essential Diagnostic Workup

Before or concurrent with treatment, the following must be performed 1:

• Serologic test for syphilis (mandatory for all genital ulcers, as 10% of chancroid patients are coinfected with T. pallidum) 1
• Darkfield examination or direct immunofluorescence for Treponema pallidum 1
• Culture for Haemophilus ducreyi (though sensitivity is only 80% even with special media) 1
• HIV testing (chancroid is a well-established cofactor for HIV transmission, with high coinfection rates) 1
• HSV culture or antigen test (to exclude herpes, as 3-10% have multiple concurrent infections) 1

Clinical Pitfall: Empiric Dual Treatment

If the diagnosis is uncertain or diagnostic capabilities are limited, treat empirically for BOTH chancroid and syphilis, especially in communities with notable chancroid morbidity 1. This means:

• Chancroid treatment (as above) PLUS
• Benzathine penicillin G 2.4 million units IM as a single dose for presumptive early syphilis 2

This dual approach is critical because diagnosis based on history and physical examination alone is often inaccurate, and at least one-quarter of genital ulcer patients have no laboratory-confirmed diagnosis even after complete testing 1.

If Syphilis is Confirmed Instead

Should serologic testing ultimately confirm primary syphilis (which would be atypical given the painful presentation):

• Benzathine penicillin G 2.4 million units IM in a single dose is the treatment of choice 2
• For penicillin-allergic patients: Doxycycline 100 mg orally twice daily for 14 days 2, 5
• Alternative for penicillin allergy: Tetracycline 500 mg orally four times daily for 14 days 1

Follow-Up Requirements

• Clinical follow-up until complete resolution of signs and symptoms 1
• Repeat serologic testing for syphilis at 3 and 6 months if initial test was negative (to detect seroconversion in the window period) 1
• HIV testing should be repeated if initially negative, given the strong association between chancroid and HIV acquisition 1

Sex Partner Management

• All sexual contacts within 10 days preceding symptom onset should be examined and treated, even if asymptomatic 1
• Partners should receive the same chancroid treatment regimen regardless of symptoms 1