Cloxacillin Sodium

Also known as: Orbenin, Tegopen, Cloxapen, Bioclox (veterinary intramammary)

CAS Number: 642-78-4

Penicillinase-Resistant Isoxazolyl Penicillin (Beta-Lactam)

Pharmacopeia Standards

USPBPIPEP

Mechanism of Action

The bulky 3-(2-chlorophenyl)-5-methylisoxazolyl side chain sterically shields the beta-lactam ring from staphylococcal penicillinase, preserving activity against penicillin-resistant Staphylococcus aureus. The intact ring then acylates penicillin-binding proteins, particularly PBP2 and PBP3, blocking peptidoglycan cross-linking. Activity against Gram-negative organisms is negligible, so use is deliberately narrow-spectrum.

Technical Specifications

Generic / INN Name	Cloxacillin Sodium
CAS Registry Number	642-78-4
Molecular Formula	C19H17ClN3NaO5S
Molecular Weight	457.86 g/mol (anhydrous); 475.88 g/mol (monohydrate) g/mol
Typical Purity	NLT 90.0% cloxacillin sodium calculated on the anhydrous basis; related substances per EP limits
Storage Conditions	Store below 25 C in tight, light-resistant containers; protect from moisture and heat.
Shelf Life	36 months for non-sterile grade; 24 months for sterile grade
Category	Penicillins

Specifications are indicative and intended for sourcing reference only. Always confirm against the supplier's Certificate of Analysis and the applicable pharmacopeial monograph before issuing a purchase specification.

Typical Applications

Oral capsules and dry syrups; sterile powder for injection; veterinary intramammary syringes for bovine mastitis; fixed-dose combinations with ampicillin sodium.