FDA approved Bicillin L-A (penicillin G benzathine) for Streptococcal Infections and SyphilisFDA approved Bicillin L-A for certain bacterial infections and prevention.

FDA From the archive Source published June 27, 1952 Summary added July 1, 2026 DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

AI-generated summary of the cited source, checked by automated accuracy review. How we work

Key Takeaway

Note: Bicillin L-A is for intramuscular use only; IV administration can cause cardiorespiratory arrest and death.

The FDA has approved Bicillin L-A (penicillin G benzathine) for the treatment of infections due to penicillin-G-sensitive microorganisms susceptible to the low and prolonged serum levels provided by this dosage form. Indications include mild-to-moderate upper respiratory tract infections caused by susceptible streptococci, venereal infections such as syphilis, yaws, bejel, and pinta, and prophylaxis for rheumatic fever and acute glomerulonephritis. The approval underscores the importance of using Bicillin L-A only for proven or strongly suspected bacterial infections to reduce the development of drug-resistant bacteria. Clinicians should note that this product is for intramuscular use only; inadvertent intravenous administration has been associated with cardiorespiratory arrest and death.

＋ Clinical Details (Mechanism · Dosing · Trial Data · Warnings)

Mechanism of Action

Penicillin G benzathine is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to cell lysis and death. It is active against penicillin-G-sensitive microorganisms.

Indication & Patient Population

Bicillin L-A is indicated for mild-to-moderate upper respiratory tract infections due to susceptible streptococci; venereal infections including syphilis, yaws, bejel, and pinta; and prophylaxis of rheumatic fever and acute glomerulonephritis. It should be used only for infections proven or strongly suspected to be caused by bacteria.

Dosing & Administration

For streptococcal upper respiratory infections: adults receive a single injection of 1,200,000 units; older pediatric patients receive 900,000 units; infants and children under 60 lbs receive 300,000 to 600,000 units. For primary, secondary, and latent syphilis: 2,400,000 units as a single dose. For late syphilis (tertiary and neurosyphilis): 2,400,000 units at 7-day intervals for three doses. For congenital syphilis in children under 2 years: 50,000 units/kg; ages 2 to 12 years: adjust based on adult schedule. For yaws, bejel, and pinta: 1,200,000 units as a single injection. For rheumatic fever prophylaxis: 1,200,000 units once monthly or 600,000 units every 2 weeks. Administer by deep intramuscular injection only; do not inject intravenously or into or near an artery or nerve.

Key Clinical Trial Data

Trial data not available in label.

Warnings & Contraindications

Contraindicated in patients with hypersensitivity to penicillins. Warnings include risk of anaphylaxis, severe cutaneous adverse reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS, AGEP), and Clostridioides difficile-associated diarrhea. Not for intravenous use; inadvertent IV administration has caused cardiorespiratory arrest and death.

Place in Therapy

Bicillin L-A is a long-acting penicillin formulation used for specific infections where prolonged low serum levels are effective. It is a first-line option for syphilis and rheumatic fever prophylaxis. Due to the risk of severe hypersensitivity reactions, careful patient history is required before use.

The FDA has approved Bicillin L-A, a form of penicillin, for treating certain bacterial infections. This includes mild-to-moderate upper respiratory infections like strep throat, sexually transmitted infections such as syphilis, and other conditions like yaws. It is also approved to prevent rheumatic fever and a kidney disease called acute glomerulonephritis.

Bicillin L-A is given as an injection into a muscle. It is important that this medicine is only used for infections that are proven or strongly suspected to be caused by bacteria. Using it for other infections, like viruses, can lead to drug-resistant bacteria, making future infections harder to treat.

This approval means doctors have another option for treating these infections. However, it is not a new drug; it is a familiar antibiotic now formally approved for these uses. Patients should talk to their doctor about whether Bicillin L-A is right for their specific infection.

A critical safety note: Bicillin L-A must never be given into a vein. Accidental injection into a vein has caused serious heart and breathing problems, even death. Always make sure your healthcare provider knows your full medical history before receiving this medicine.

What this means for you:

Bicillin L-A is a penicillin shot for certain bacterial infections and prevention; use only as prescribed.

Study Details

Study typeFda approval

PublishedJun 1952

View Original Abstract ↓

INDICATIONS AND USAGE To reduce the development of drug-resistant bacteria and maintain the effectiveness of Bicillin L-A and other antibacterial drugs, Bicillin L-A should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Intramuscular penicillin G benzathine is indicated in the treatment of infections due to penicillin-G-sensitive microorganisms that are susceptible to the low and very prolonged serum levels common to this particular dosage form. Therapy should be guided by bacteriological studies (including sensitivity tests) and by clinical response. The following infections will usually respond to adequate dosage of intramuscular penicillin G benzathine: Mild-to-moderate infections of the upper-respiratory tract due to susceptible streptococci. Venereal infections —Syphilis, yaws, bejel, and pinta. Medical Conditions in which Penicillin G Benzathine Therapy is indicated as Prophylaxis: Rheumatic fever and/or chorea —Prophylaxis with penicillin G benzathine has proven effective in preventing recurrence of these conditions. It has also been used as follow-up prophylactic therapy for rheumatic heart disease and acute glomerulonephritis.

FDA approved Bicillin L-A (penicillin G benzathine) for Streptococcal Infections and SyphilisFDA approved Bicillin L-A for certain bacterial infections and prevention.

Study Details

Intrawound tobramycin plus vancomycin did not reduce deep infection risk compared with vancomycin alone in high-risk tibial fractures

Adding Antibiotics to Bone Surgery Didn't Lower Infection Risk

Clinical research that matters. Delivered to your inbox.

FDA approved Bicillin L-A (penicillin G benzathine) for Streptococcal Infections and SyphilisFDA approved Bicillin L-A for certain bacterial infections and prevention.

Study Details

Intrawound tobramycin plus vancomycin did not reduce deep infection risk compared with vancomycin alone in high-risk tibial fractures

Adding Antibiotics to Bone Surgery Didn't Lower Infection Risk

Clinical research that matters. Delivered to your inbox.

Related in Infectious Disease

From Other Specialties