Syphilis Treatment and Persistent Vomiting: Seek Immediate Medical Advice

Vomiting after syphilis treatment is NOT a typical penicillin side effect and requires urgent evaluation.

Standard Syphilis Treatment

• Primary/secondary/early latent: Benzathine penicillin G 2.4 MU IM single dose.
• Late latent/tertiary: 3 doses weekly.
• Neurosyphilis: Aqueous penicillin G 18–24 MU IV daily × 10–14 days.

Common Penicillin Side Effects

• Jarisch-Herxheimer reaction (fever, chills, myalgia, headache, hypotension) — 2–12 hrs post-injection, self-limited.
• Injection site pain, local reaction.
• Allergic reactions (rash, anaphylaxis) — rare.
• Nausea is uncommon with IM penicillin; vomiting is rare.

Vomiting May Indicate

• Allergic reaction: Especially if + rash, swelling, dyspnea, hypotension → anaphylaxis (emergency).
• Other infection: Gastroenteritis, appendicitis, etc.
• Pregnancy: Hyperemesis, ectopic.
• Medication interaction.
• Neurosyphilis complications.

Action

Call your provider immediately or go to ER. Do not assume it's "just the shot." Timely assessment prevents missed serious conditions.