1 May 2026Injectable drugsSource update: June 2025
Benzylpenicillin = Penicillin G injectable
Short-acting benzylpenicillin guidance for diphtheria, severe leptospirosis, neurosyphilis, and congenital syphilis.
Prescription under medical supervision
This guide page is for structured reference only and does not replace a clinician, pharmacist, or emergency review. Dose choice, route choice, interactions, and safety decisions still need professional judgment.
Therapeutic action
Short-acting penicillin antibacterial.
Indications
- Diphtheria, when oral treatment is not possible.
- Severe leptospirosis and neurosyphilis.
- Congenital syphilis when the neonate has clinical signs or the mother did not receive adequate treatment.
Forms and strengths, route of administration
- Powder for injection in 1 MIU and 5 MIU vials.
- For IM injection, slow IV injection through an infusion tube, or IV infusion in 0.9% sodium chloride or 5% glucose.
Dose
Diphtheria
- Child: 25,000 IU/kg by IM or IV injection every 6 hours, maximum 1 MIU.
- Adult: 1 MIU by IM or IV injection every 6 hours.
Severe leptospirosis
- Child: 50,000 IU/kg by IV injection every 6 hours, maximum 2 MIU.
- Adult: 1 to 2 MIU by IV injection every 6 hours.
Neurosyphilis
- Adult: 2 to 4 MIU by IV injection every 4 hours.
Congenital syphilis
- 50,000 IU/kg by IV injection every 12 hours from D1 to D7.
- Then 50,000 IU/kg by IV injection every 8 hours from D8 to D10.
Duration
- Diphtheria: change to oral treatment as soon as the patient can swallow, to complete 14 days.
- Severe leptospirosis: 7 days.
- Neurosyphilis: 14 days.
- Congenital syphilis: 10 days.
Contra-indications, adverse effects, precautions
- Once reconstituted, suspension must be used immediately.
- Do not administer to penicillin-allergic patients.
- Administer with caution to patients allergic to cephalosporins and to patients with renal impairment.
- May cause gastrointestinal disturbances, pain at injection site, anaemia, allergic reactions, Jarisch-Herxheimer reaction, and convulsions in the event of rapid IV injection, high dosages, or renal impairment.
- Do not combine with methotrexate.
- Pregnancy and breast-feeding: no contra-indication.
- Do not confuse short-acting benzylpenicillin with long-acting penicillins.
- Do not mix with other drugs in the same syringe or infusion.
Source
MSF Essential drugs practical guidelines (January 2026)
This page reproduces the structured reference information for this batch while leaving out the Storage and Remarks sections.
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