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Trade namesGeocillin
  • (2S,5R,6R)-6-{[carboxy(phenyl)acetyl]amino}-
    heptane-2-carboxylic acid
Clinical data
  • US: B (No risk in non-human studies)
Routes of
Oral, parenteral
External links
Legal status
  • In general: ℞ (Prescription only)
Bioavailability30 to 40%
Protein binding30 to 60%
Elimination half-life1 hour
ExcretionKidney (30 to 40%)
Chemical and physical data
Molar mass378.40 g·mol−1
3D model (JSmol)
  • O=C(O)[C@@H]2N3C(=O)[C@@H](NC(=O)C(c1ccccc1)C(=O)O)[C@H]3SC2(C)C
  • InChI=1S/C17H18N2O6S/c1-17(2)11(16(24)25)19-13(21)10(14(19)26-17)18-12(20)9(15(22)23)8-6-4-3-5-7-8/h3-7,9-11,14H,1-2H3,(H,18,20)(H,22,23)(H,24,25)/t9?,10-,11+,14-/m1/s1 checkY

Carbenicillin is an antibiotic.[1] It is given by mouth.[1]

It requires high doses and is potentially toxic.[1] It is a bactericidal antibiotic belonging to the carboxypenicillin subgroup of the penicillins. It has Gram-negative coverage which includes Pseudomonas aeruginosa but limited Gram-positive coverage. The carboxypenicillins are susceptible to degradation by beta-lactamase enzymes, although they are more resistant than ampicillin to degradation. Carbenicillin is also more stable at lower pH than ampicillin.

It came into use in 1970 as the first penicillin able to act against P. aeruginosa.[2] It is generally no longer in use as better alternatives are available.[1]


The antibiotic is highly soluble in water and is acid-labile. A typical lab working concentration is 50 µg per ml.

It is a semi-synthetic analogue of the naturally occurring benzyl-penicillin. Carbenicillin at high doses can cause bleeding. Use of carbenicillin can cause hypokalemia by promoting potassium loss at the distal convoluted tubule of the kidney.

In molecular biology, carbenicillin may be preferred as a selecting agent (see Plasmid stabilisation technology) because its breakdown results in byproducts with a lower toxicity than analogous antibiotics like ampicillin. Carbenicillin is more stable than ampicillin and results in fewer satellite colonies on selection plates. However, in most situations this is not a significant problem so ampicillin is sometimes used due to its lower cost.

Spectrum of bacterial susceptibility and resistance

Carbenicillin has been shown to be effective against bacteria responsible for causing urinary tract infections including Pseudomonas aeruginosa, Escherichia coli, and some Proteus species. The following represents carbenicillin susceptibility data for a few medically significant organisms. This is not representative of all species of bacteria susceptible to carbenicillin exposure.

  • Escherichia coli 1.56 μg/ml - 64 μg/ml
  • Proteus mirabilis 1.56 μg/ml - 3.13 μg/ml
  • Pseudomonas aeruginosa 3.13 μg/ml - >1024 μg/ml



It came into use in 1970 as the first penicillin able to act against P. aeruginosa.[2] It was discovered by scientists at Beecham and marketed as Pyopen.


  1. 1.0 1.1 1.2 1.3 Eliopoulos, George M.; Moellering Jr, Robert C. (2015). "17. Principles of anti-infective therapy". In Bennett, John E.; Dolin, Raphael; Blaser, Martin J. (eds.). Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Vol. 1 (8th ed.). Elsevier. p. 273. ISBN 978-1-4557-4801-3. Archived from the original on 2021-12-11. Retrieved 2021-12-01.
  2. 2.0 2.1 Endres, Tori M.; Toltzis, Philip (1 November 2021). "50 Years Ago in The Journal of Pediatrics: Carbenicillin and Cystic Fibrosis". The Journal of Pediatrics. 238: 214. doi:10.1016/j.jpeds.2021.08.043. ISSN 0022-3476. Archived from the original on 11 December 2021. Retrieved 1 December 2021. Cite error: Invalid <ref> tag; name "Endres2021" defined multiple times with different content
  3. "Archive copy" (PDF). Archived (PDF) from the original on 2018-11-11. Retrieved 2021-05-19.{{cite web}}: CS1 maint: archived copy as title (link)

Further reading

  • Basker MJ, Comber KR, Sutherland R, Valler GH (1977). "Carfecillin: antibacterial activity in vitro and in vivo". Chemotherapy. 23 (6): 424–35. doi:10.1159/000222012. PMID 21771.
  • Pawełczyk E, Zajac M, Knitter B, Mikołajczak P (October 1981). "Kinetics of drug decomposition. Part 66. Kinetics of the hydrolysis of carphecillin in aqueous solution". Polish Journal of Pharmacology and Pharmacy. 33 (3): 373–86. PMID 7322950.

External links