Cloxacillin sodiumA semi-synthetic antibiotic related to penicillin

Cloxacillin sodium (CAS 7081-44-9)

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Synonym: Bactopen; Cloxapen; Cloxypen; Ekvacillin; Orbenin; Methocillin-S
Application: A semi-synthetic antibiotic related to penicillin
CAS Number: 7081-44-9
Purity: >94%
Molecular Weight: 475.55
Molecular Formula: C19H17ClN3NaO5S
* Refer to Certificate of Analysis for lot specific data (including water content).
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Cloxacillin is a semi-synthetic β-lactam antibiotic, related to penicillin, which suppresses the growth of gram-positive bacteria such as Staphylococcus by inhibiting the synthesis of peptidoglycan. Furthermore, cloxacillin inactivates the enzyme β-lactamase I, a side product produced by bacteria that are resistant to β-lactam antibiotics, by causing the acyl form of the enzyme to unfold. Escherichia coli containing plasmids carrying non-coding DsrA RNA are resistant to Cloxacilin. Cloxacillin sodium is an inhibitor of LACTB.


1. Sabath, L.D., et al. 1976. Antimicrob. Agents Chemother. 9: 962-969. PMID: 938025
2. Kiener, P.A., et al. 1980. Eur. J. Biochem. 109: 575-580. PMID: 6773776
3. Rasmussen, B.A., et al. 1994. Antimicrob. Agents Chemother. 38: 2078-2085. PMID: 7811022
4. Nishino, K., et al. 2010. J. Antimicrob. Chemother. [Epub ahead of print]. PMID: 21088020

Appearance :
Crystalline powder
Physical State :
Solubility :
Soluble in water (55 mg/ml at 25° C), alcohol (1:30), methanol, ethanol (25 mg/ml at 25° C), and DMSO (55 mg/ml at 25° C).
Storage :
Store at 4° C
Melting Point :
170° C (dec.)
Boiling Point :
689.7° C at 760 mmHg (Predicted)
Refractive Index :
n20D 1.69 (Predicted)
Optical Activity :
α20/D +164.5°±4.5°, c = 1 in water
IC50 :
Class C β-lactamase CMY-36: IC50 = 4 nM (Klebsiella pneumoniae); CMY-2 : IC50 = 4 nM; Efflux transporter: IC50 = 4 nM (Salmonella ); β-lactamase ACC-4: IC50 = 26 nM (Escherichia ); Staphylococcus aureus: IC50 = 8.9 µg/ml
Ki Data :
Escherichia coli MC4100 β-Lactamase CMY-2: Ki= 0.2 nM; Escherichia coli MC4100 β-Lactamase CMY-30 : Ki= 2.3 nM; β-lactamase TEM: Ki= 13 µM (Escherichia coli); Oligopeptide transporter, kidney isoform: Ki= 950 µM (rat); PEPT2: Ki= 950 µM (human)
For Research Use Only. Not Intended for Diagnostic or Therapeutic Use.
WGK Germany :
PubChem CID :
Merck Index :
14: 2419
MDL Number :
EC Number :

Download SDS (MSDS)

Certificate of Analysis

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