Penicillin G
Clinical data
Trade names BenPen
AHFS/ Micromedex Detailed Consumer Information
MedlinePlus a685013
  • AU: A
  • US: B (No risk in non-human studies)
Routes of
Intravenous, Intramuscular, formerly used orally
ATC code J01CE01 (WHO) S01AA14 (WHO) QJ51CE01 (WHO)
Legal status
Legal status
  • ℞ (Prescription only)
Pharmacokinetic data
Protein binding 60 %
Metabolism hepatic
Biological half-life 30 min
Excretion renal
CAS Number 61-33-6 YesY (free acid)
69-57-8 (sodium salt)
PubChem (CID) 5904
DrugBank DB01053 YesY
ChemSpider 5693 YesY
KEGG D02336 N
E number E705 (antibiotics)
Chemical and physical data
Formula C16H18N2O4S
Molar mass 334.4 g/mol
3D model (Jmol) Interactive image
 NYesY (what is this?)  (verify)
2,400,000 units of Bicillin L-A brand of benzylpenicillin, for deep intramuscular injection

Benzylpenicillin (INN, AAN, BAN), also known as penicillin G (USAN), is a narrow spectrum penicillin antibiotic that is given intravenously or intramuscularly as a treatment for syphilis, meningitis, endocarditis, pneumonia, lung abscesses and septicaemia in children.[1] Penicillin G is typically given by injection parenterally, bypassing the intestines, because it is unstable in the highly acidic stomach. Because the drug is given parenterally, higher tissue concentrations of penicillin G can be achieved than is possible with phenoxymethylpenicillin. These higher concentrations translate to increased antibacterial activity.

It is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system.[2]

Medical uses

Antimicrobial potency

As an antibiotic, Penicillin G is noted to possess effectiveness mainly against Gram-positive organisms. Some Gram-negative organisms such as Neisseria gonorrhoeae and Neisseria meningitidis are also reported to be susceptible to Penicillin G.[3]

Adverse effects

Adverse effects can include hypersensitivity reactions including urticaria, fever, joint pains, rashes, angioedema, anaphylaxis, serum sickness-like reaction. Rarely CNS toxicity including convulsions (especially with high doses or in severe renal impairment), interstitial nephritis, haemolytic anaemia, leucopenia, thrombocytopenia, and coagulation disorders. Also reported diarrhoea (including antibiotic-associated colitis).

Benzylpenicillin serum concentrations can be monitored either by traditional microbiological assay or by more modern chromatographic techniques. Such measurements can be useful to avoid central nervous system toxicity in any person receiving large doses of the drug on a chronic basis, but they are especially relevant to patients with renal failure, who may accumulate the drug due to reduced urinary excretion rates.[4][5]


  1. Rossi, S, ed. (2013). Australian Medicines Handbook (2013 ed.). Adelaide: The Australian Medicines Handbook Unit Trust. ISBN 978-0-9805790-9-3.
  2. "WHO Model List of Essential Medicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014.
  3. "Penicillin G" (pdf). Toku-E. 2010-10-10. Retrieved 2012-06-11.
  4. Fossieck B Jr, Parker RH. Neurotoxicity during intravenous infusion of penicillin. A review. J. Clin. Pharmacol. 14: 504- 512, 1974.
  5. R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 1195-1196.
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