penicillin G benzathine (Bicillin L-A)

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

GENERIC NAME: penicillin G benzathine injectable suspension

BRAND NAME: Bicillin L-A

DRUG CLASS AND MECHANISM: Penicillin G benzathine (Bicillin L-A) is a penicillin antibiotic that is given by deep intramuscular injection. Penicillin G benzathine kills susceptible bacteria by inhibiting the synthesis or formation of bacterial cell wall. It is thought to preferentially bind to specific penicillin-binding proteins (PBPs) found inside the bacterial cell wall. The end result of the inhibition of bacterial cell synthesis is cell lysis and the death of the susceptible bacteria.

Penicillin G benzathine has poor solubility and is therefore very slowly released from the site of injection. In the blood, penicillin G benzathine is broken down to penicillin G. Penicillin G benzathine formulation is released and absorbed slowly to allow for a more prolonged duration of action (drug works slowly over an longer period of time).


GENERIC AVAILABLE: Not available in the US

PREPARATIONS: Penicillin G benzathine injectable suspension: 1 ml (600,000 units per syringe), 2 ml (1,200,000 units per syringe), and 4 ml (2,400,000 units per syringe).

STORAGE: Suspension should be stored in a refrigerator, between 2 C and 8 C (36 F and 86 F).


Intramuscular penicillin G benzathine is used to treat the following conditions:

Penicillin G benzathine is also used for prevention of rheumatic fever or chorea.


  • Streptococcal (Group A) upper respiratory infections: Adult patients are administered a single injection of 1,200,000 units; older pediatric patients are administered a single injection of 900,000 units; infants and pediatric patients < 60 Ibs are administered 300,000 to 600,00 units.
  • Syphilis: For the treatment of primary, secondary, and latent syphilis the recommended dose is 2,400,000 units as a one-time dose. For the treatment of tertiary and neurosyphilis the recommended dose is 2,400,000 every 7 days for a total of three doses. For the treatment of congenital syphilis in patients under the age of 2, the recommended dose is 50,000 units/kg.
  • Yaws, Bejel, and Pinta: The recommended dose is 1,200,000 units administered as a single injection.
  • Prevention of rheumatic fever and glomerulonephritis: After an acute attack, penicillin G benzathine may be given in doses of 1,200,000 units once a month or 600,000 units every 2 weeks.

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