Carbenicillin is a bactericidal antibiotic belonging to the carboxypenicillin subgroup of the penicillins.^[2] It was discovered by scientists at Beecham and marketed as Pyopen. 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.

Quick Facts Clinical data, Trade names ...

Carbenicillin

Clinical data
Trade names	Geocillin; Pyopen
Other names	CB[1]
AHFS/Drugs.com	Monograph
Pregnancy category	Passes into breast milk
Routes of administration	Oral, parenteral
ATC code	J01CA03 (WHO)
Legal status
Legal status	In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability	30 to 40%
Protein binding	30 to 60%
Metabolism	Minimal
Elimination half-life	1 hour
Excretion	Renal (30 to 40%)
Identifiers
IUPAC name (2S,5R,6R)-6-{[carboxy(phenyl)acetyl]amino}- 3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0] heptane-2-carboxylic acid
CAS Number	4697-36-3 Y
PubChem CID	20824
DrugBank	DB00578 Y
ChemSpider	19599 Y
UNII	G42ZU72N5G
KEGG	D07614 N
ChEBI	CHEBI:3393 Y
ChEMBL	ChEMBL1214 Y
CompTox Dashboard (EPA)	DTXSID6048464
ECHA InfoCard	100.022.882
Chemical and physical data
Formula	C17H18N2O6S
Molar mass	378.40 g·mol−1
3D model (JSmol)	Interactive image
SMILES O=C(O)[C@@H]2N3C(=O)[C@@H](NC(=O)C(c1ccccc1)C(=O)O)[C@H]3SC2(C)C
InChI 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 Y Key:FPPNZSSZRUTDAP-UWFZAAFLSA-N Y
NY (what is this?)  (verify)

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The antibiotic is highly soluble in water and is acid-labile. A typical lab working concentration is 50 to 100 μg per mL.^{[citation needed]}

It is a semi-synthetic analogue of the naturally occurring benzylpenicillin. 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.^{[citation needed]}

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.^{[citation needed]}

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.^[3] 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