Penicillin G
Penicillin G is a beta-lactam antibiotic used to treat serious bacterial infections caused by susceptible organisms. It is commonly administered intravenously or intramuscularly in healthcare settings for conditions such as syphilis, meningitis, endocarditis, and severe streptococcal infections. This medication is reserved for cases where the causative organism has been identified as susceptible, as many bacteria have developed resistance.
Penicillin G is an injectable antibiotic that kills susceptible bacteria by disrupting their cell wall synthesis, used primarily for serious infections like syphilis, meningitis, and certain streptococcal diseases.
This medication carries a boxed (black box) warning — the strongest type of FDA warning. Review the full prescribing information before use.
Key facts at a glance
- ATC
- J01CE01
- RxNorm
- 7980
- Generic
- Penicillin G
- Class
- atc-j01
- Brands
- Bactracillin G, Norocillin, Albadry, Quartermaster, Bicillin L-A, Bicillin, Extencilline, Lentocilin, Pfizerpen
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- prefilled syringe, injection, suspension, tablet, solution
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesterno adjustment needed
generally considered safe for use in pregnancy when indicated
standard prenatal monitoring
pregnancy
second trimesterno adjustment needed
generally considered safe for use in pregnancy when indicated
standard prenatal monitoring
pregnancy
third trimesterno adjustment needed
generally considered safe for use in pregnancy when indicated
standard prenatal monitoring
lactation
breastfeedingno adjustment needed
generally considered safe, small amounts excreted in breast milk
monitor infant for GI disturbances or allergic reactions
geriatric
elderlyadjust dose based on renal function
use with caution due to potential age-related decline in renal function
monitor renal function and adjust dose accordingly
Use with caution and monitor for adverse effects.
pediatric_age
neonates and infantsdose based on weight and age
generally safe for use in pediatric patients
standard pediatric monitoring
renal_impairment
mild to moderatemay require dose adjustment in moderate impairment
use with caution, adjust dose based on creatinine clearance
monitor renal function and consider drug levels in severe impairment
Use with caution and monitor for adverse effects.
hepatic_impairment
moderate to severeno major adjustment needed
primarily renally excreted, hepatic impairment does not significantly affect clearance
standard monitoring
Statistics and clinical data
Drug class
Classification based on mechanism of action
Mechanism of action
Pharmacodynamic mechanism
Common uses
Primary therapeutic indications
Formulation
Physical form and salt preparation
Penicillin G is used to treat syphilis (including neurosyphilis), bacterial meningitis, infections caused by susceptible streptococci and staphylococci, diphtheria, anthrax, actinomycosis, and Lyme disease in its later stages. It is often used when the infecting organism has been confirmed to be susceptible through laboratory testing.
Penicillin G binds to specific penicillin-binding proteins (PBPs) in the bacterial cell wall, inhibiting the synthesis of peptidoglycan, which is essential for maintaining cell wall integrity. This results in osmotic instability and bacterial cell death during active multiplication.
Penicillin G should not be used in patients with known penicillin allergy due to risk of severe allergic reactions including anaphylaxis. Cross-reactivity may occur with other beta-lactam antibiotics. Sodium content should be considered in patients on sodium-restricted diets, and renal function should be monitored during prolonged therapy. Administered only by intravenous or intramuscular injection under medical supervision.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy