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Penicillin-G 3D.png
Systematic (IUPAC) name
(2S,5R,6R)-3,3-dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid
Clinical data
Trade names BenPen
AHFS/ Micromedex Detailed Consumer Information
MedlinePlus a685013
  • AU: A
  • US: B (No risk in non-human studies)
Legal status
  • ℞ (Prescription only)
Routes of
Intravenous, Intramuscular, formerly used orally
Pharmacokinetic data
Protein binding 60 %
Metabolism hepatic
Biological half-life 30 min
Excretion renal
CAS Number 61-33-6 YesY (free acid)
Template:CAS (sodium salt)
ATC code J01CE01 (WHO) S01AA14 QJ51CE01 (WHO)
PubChem CID: 5904
DrugBank DB01053 YesY
ChemSpider 5693 YesY
KEGG D02336 N
Chemical data
Formula C16H18N2O4S
Molecular mass 334.4 g/mol
 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

Specific indications for benzylpenicillin include:[3]

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.[4]

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.[5][6]

Compendial status


  1. Rossi, S, ed. (2013). Australian Medicines Handbook (2013 ed.). Adelaide: The Australian Medicines Handbook Unit Trust. ISBN 978-0-9805790-9-3.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. "WHO Model List of Essential Medicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. Rossi S, editor, ed. (2006). Australian Medicines Handbook. Adelaide: Australian Medicines Handbook. ISBN 0-9757919-2-3.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. "Penicillin G" (pdf). Toku-E. 10 October 2010. Retrieved 11 June 2012.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  5. Fossieck B Jr, Parker RH. Neurotoxicity during intravenous infusion of penicillin. A review. J. Clin. Pharmacol. 14: 504- 512, 1974.
  6. R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 1195-1196.
  7. British Pharmacopoeia Commission Secretariat. "Index (BP 2009)" (PDF). Retrieved 26 March 2010.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>