Benzathine benzylpenicillin

Long-acting Penicillin·Infectious Diseases - Penicillins

Syphilis (all stages except neurosyphilis), secondary prophylaxis of rheumatic fever

Authority requiredPBSBETA-LACTAMBicillin L-A900 mg+2

Max Dose

2.4 MU STAT

Duration

2-4 WEEKS

Route

IM ONLY

IV Route

FATAL

Rapid Summary

Overview

An extremely long-acting, highly insoluble depot formulation of Penicillin G. Slowly leaches into the blood over weeks to provide low-level, continuous bactericidal cover.

Maximum Dose

Max 2.4 Million Units (MU) per dose.

Clinical Focus

Must NEVER be given IV. Accidental IV injection of this thick, milky suspension causes instant fatal cardiopulmonary arrest and microembolization.

Bottom Line

Benzathine benzylpenicillin is the gold-standard IM depot penicillin for rheumatic fever prophylaxis and syphilis, but must never be given IV (fatal embolic reaction) and IM injection is painful.

Formulation & Access

Brand Names

Bicillin L-A

Parenteral

Pre-filled syringe (1.2 MU / 900 mg) for deep IM injection ONLY. Store in the fridge.

Prescribing & PBS

Authority Required (PBS).

Indications & Use

Primary

PBSTGA

Syphilis (all stages except neurosyphilis), secondary prophylaxis of rheumatic fever.

Clinical Place

The absolute gold standard for Syphilis. Unmatched efficacy; overcomes patient non-compliance by requiring only 1-3 injections.

Quick reference

Class & Role

Long-acting Penicillin — An extremely long-acting, highly insoluble depot formulation of Penicillin G.

Route / Formulation

Pre-filled syringe (1.2 MU / 900 mg) for deep IM injection ONLY. Store in the fridge. (Bicillin L-A)

Usual Dose & Max

IM 1.8 g (2.4 MU) STAT as a single deep intramuscular injection. Max 2.4 Million Units (MU) per dose.

Key Indication Doses

Early Syphilis: IM 1.8 g (2.4 MU) STAT as a single deep intramuscular injection. Late Latent Syphilis: IM 1.8 g (2.4 MU) ONCE WEEKLY for 3 weeks. Rheumatic Fever Prophylaxis: IM 900 mg (1.2 MU) every 3-4 weeks.

Best Uses

Benzathine benzylpenicillin is the gold-standard IM depot penicillin for rheumatic fever prophylaxis and syphilis, but must never be given IV (fatal embolic reaction) and IM injection is painful.

Avoid / Cautions

Intravenous administration. Severe penicillin allergy. Pregnancy Category A. Mandatory treatment to prevent congenital syphilis.

Key Risks

Tissue: Exquisitely painful injection. Can cause severe sterile abscesses or nerve damage if not given deeply into a large muscle mass. Immunological: Anaphylaxis (and if it occurs, the depot continues releasing drug for weeks!). Systemic: Jarisch-Herxheimer reaction (fever, chills, myalgia within 24h of treating syphilis due to massive bacterial die-off).

Key Interactions

Extremely low systemic blood levels mean drug interactions are virtually non-existent.

Monitoring

Aspirate the syringe prior to injection. If blood appears, withdraw completely and discard the syringe. Do not inject into a blood vessel. Warn patients treating syphilis about the Jarisch-Herxheimer reaction (it is not an allergy; treat with Paracetamol).

Clinical Pearl

Do NOT confuse Bicillin L-A (Long-Acting Benzathine) with Bicillin C-R (Combo of Benzathine and Procaine). Bicillin C-R has a much shorter duration and is completely inadequate for treating Syphilis. Always double-check the box!

Access

Authority requiredBicillin L-A

Brand: Bicillin L-A
PBS status: Authority required

Benzathine benzylpenicillin

Long-acting Penicillin·Infectious Diseases - Penicillins

Syphilis (all stages except neurosyphilis), secondary prophylaxis of rheumatic fever

Authority requiredPBSBETA-LACTAMBicillin L-A900 mg+2

Max Dose

2.4 MU STAT

Duration

2-4 WEEKS

Route

IM ONLY

IV Route

FATAL

Rapid Summary

Overview

An extremely long-acting, highly insoluble depot formulation of Penicillin G. Slowly leaches into the blood over weeks to provide low-level, continuous bactericidal cover.

Maximum Dose

Max 2.4 Million Units (MU) per dose.

Clinical Focus

Must NEVER be given IV. Accidental IV injection of this thick, milky suspension causes instant fatal cardiopulmonary arrest and microembolization.

Bottom Line

Benzathine benzylpenicillin is the gold-standard IM depot penicillin for rheumatic fever prophylaxis and syphilis, but must never be given IV (fatal embolic reaction) and IM injection is painful.

Formulation & Access

Brand Names

Bicillin L-A

Parenteral

Pre-filled syringe (1.2 MU / 900 mg) for deep IM injection ONLY. Store in the fridge.

Prescribing & PBS

Authority Required (PBS).

Indications & Use

Primary

PBSTGA

Syphilis (all stages except neurosyphilis), secondary prophylaxis of rheumatic fever.

Clinical Place

The absolute gold standard for Syphilis. Unmatched efficacy; overcomes patient non-compliance by requiring only 1-3 injections.

Quick reference

Class & Role

Long-acting Penicillin — An extremely long-acting, highly insoluble depot formulation of Penicillin G.

Route / Formulation

Pre-filled syringe (1.2 MU / 900 mg) for deep IM injection ONLY. Store in the fridge. (Bicillin L-A)

Usual Dose & Max

IM 1.8 g (2.4 MU) STAT as a single deep intramuscular injection. Max 2.4 Million Units (MU) per dose.

Key Indication Doses

Best Uses

Benzathine benzylpenicillin is the gold-standard IM depot penicillin for rheumatic fever prophylaxis and syphilis, but must never be given IV (fatal embolic reaction) and IM injection is painful.

Avoid / Cautions

Intravenous administration. Severe penicillin allergy. Pregnancy Category A. Mandatory treatment to prevent congenital syphilis.

Key Risks

Key Interactions

Extremely low systemic blood levels mean drug interactions are virtually non-existent.

Monitoring

Clinical Pearl

Access

Authority requiredBicillin L-A

Brand: Bicillin L-A
PBS status: Authority required