Complications table

Jarisch-Herxheimer reaction

short termhigh

Occurs within the first 24 hours after antibiotic therapy due to the rapid killing of treponemes.

Characterised by acute fever, headache, and myalgia, usually in patients with early syphilis.

The likelihood of reaction is high in early syphilis but low in late syphilis. However, all patients should be advised of a possible reaction prior to receiving antibiotic treatment.

In pregnant women, Jarisch-Herxheimer reaction may cause fetal distress and premature labour.

Treatment is supportive with oral fluids, paracetamol (acetaminophen), and non-steroidal anti-inflammatory drugs. 

Corticosteroid therapy may be considered to minimise the risk of a Jarisch-Herxheimer reaction in non-pregnant patients with cardiovascular syphilis or neurosyphilis.[3] However, the evidence of effectiveness is unclear and it is not routinely recommended in some countries.

allergic reaction to penicillin

short termmedium

May arise in patients not previously known to be allergic.

In patients with penicillin allergy, alternative treatment options may be offered, dependent on the stage of syphilis.

Penicillin allergy skin testing and desensitisation may be required (e.g., in the treatment of pregnant women).

Penicillin-allergic responses may include urticaria, angio-oedema, and anaphylaxis.

Treatment of allergic reaction is determined by the severity of the reaction.

iatrogenic procaine reaction

short termlow

Occurs when intramuscular procaine benzylpenicillin (e.g., used to treat neurosyphilis) is mistakenly administered intravenously.

Patients may develop penicillin allergic responses, including anaphylactic shock.[104]

HIV infection

long termmedium

Syphilis facilitates the acquisition of HIV.

asymptomatic progression of disease


Organ-specific complications can occur in untreated infection of unknown duration.

Specialist opinion should be sought depending on the nature of the complication (e.g., ophthalmology specialist opinion for ocular infection, cardiovascular specialist opinion for aortic regurgitation).

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