ATC Code J01CE01, S01AA14
Formula C16H18N2O4S
Molar Mass (g·mol−1) 334,39
Physical State solid
Melting Point (°C) 217
PKS Value 2,74
CAS Number 61-33-6
PUB Number 5904
Drugbank ID DB01053
Solubility soluble in water


Benzylpenicillin, also known as penicillin G, is an antibiotic used to treat a number of bacterial infections. These include pneumonia, streptococcal infections, syphilis, necrotizing enterocolitis, diphtheria, gas gangrene, leptospirosis, cellulitis, and tetanus. Benzylpenicillin is administered by injection into a vein or muscle.



Benzylpenicillin acts by binding to specific penicillin-binding proteins (PBPs) located within the bacterial cell wall. As a result, penicillin G inhibits the third and final step of bacterial cell wall synthesis. This leads to cell lysis, which is mediated by autolytic enzymes of the bacterial cell wall (autolysins).


Rapidly absorbed after both intramuscular and subcutaneous injection. It is 45-68% bound to serum proteins, mainly albumin. Penicillin G is excreted by the kidneys after metabolism in the liver. In adults with normal renal function, the half-life is approximately 0.4-0.9 hours.


Side effects

Side effects include diarrhea, seizures, and allergic reactions including anaphylaxis.

When treating syphilis or Lyme disease, a reaction known as Jarisch-Herxheimer may occur. Allergic reactions may occur with the use of penicillins.

Toxicological data

LD50 (mouse, i.v.): 329 mg-kg-1


  • Drugbank
  • PubChem
  • Aktories, Förstermann, Hofmann, Starke: Allgemeine und spezielle Pharmakologie und Toxikologie, Elsvier, 2017

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Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter is a writer on pharmaceutical topics in Medikamio's medical editorial team. He is in the last semester of his pharmacy studies at the University of Vienna and loves scientific work in the field of natural sciences.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer has been a freelance writer for Medikamio since 2020 and studied pharmacy at the University of Vienna. She works as a pharmacist in Vienna and her passion is herbal medicines and their effects.

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