Apo-Cloxi , Cloxapen, Novocloxin 
Classifications: antibiotic, penicillin; beta-lactam; Therapeutic: antibiotic
Prototype: Penicillin G
Pregnancy Category: B


250 mg, 500 mg capsules; 125 mg/5 mL oral suspension


Semisynthetic, penicillinase-resistant, beta-lactam penicillin. Cloxacillin inhibits third and final stage of bacterial cell wall synthesis by preferentially binding to specific penicillin-binding proteins (PBPs) that are located within the bacterial cell wall, which results in cell lysis and therefore cell death.

Therapeutic Effect

Effective against most gram-positive bacteria. Highly active against most penicillinase-producing staphylococci, and generally ineffective against gram-negative bacteria and methicillin-resistant staphylococci (MRSA).


Primarily in infections caused by penicillinase-producing staphylococci and penicillin-resistant staphylococci. May be used to initiate therapy in suspected staphylococcal infections pending culture and susceptibility test results.


Sensitivity to penicillins; lactation. Safe use in neonates not established.

Cautious Use

History of or suspected atopy or allergy (asthma, eczema, hives, hay fever), renal or hepatic function impairment, history of allergy to cephalosporins, pregnancy (category B).

Route & Dosage

Mild to Moderate Infections
Adult: PO 250–500 mg q6h
Child (<20 kg): PO 12.5–25 mg/kg q6h (max: 4 g/d)


  • Give on an empty stomach (at least 1 h before or 2 h after meals) unless otherwise advised by physician. Food reduces rate and extent of drug absorption.
  • After reconstitution PO solution retains potency for 14 d if refrigerated (shake well before pouring).
  • Unless otherwise advised, store capsules at 15°–30° C (59°–86° F).

Adverse Effects (≥1%)

Body as a Whole: Wheezing, sneezing, chills, drug fever, anaphylaxis, superinfections. GI: Nausea, vomiting, flatulence, diarrhea. Hematologic: Eosinophilia, leukopenia, agranulocytosis. Metabolic: Elevated AST, ALT; jaundice (possibly of allergic etiology). Skin: Pruritus, urticaria, rash.


Drug: Probenecid decreases cloxacillin elimination.


Absorption: 37–60% from GI tract. Peak: 0.5–2 h. Duration: 4–6 h. Distribution: Distributed throughout body with highest concentrations in liver, kidney, spleen, bone, bile, and pleural fluid; low CSF penetration; crosses placenta; distributed into breast milk. Metabolism: In liver. Elimination: Primarily in urine; some elimination via bile. Half-Life: 30–60 min.

Nursing Implications

Assessment & Drug Effects

  • Determine previous exposure and sensitivity to penicillins and cephalosporins and other allergic reactions of any kind before treatment is initiated.
  • Monitor for S&S of anaphylactoid reaction (see Appendix G) or other signs or symptoms of hypersensitivity reaction (see Appendix F) as with other penicillins.
  • Lab tests: Periodic assessments of renal, hepatic, and hematopoietic function are advised in patients on long-term therapy.

Patient & Family Education

  • Take medication around the clock, do not miss a dose, and continue taking the medication until it is finished.
  • Report to physician the onset of hypersensitivity reaction (see Appendix F) and superinfections.
  • Check with physician if GI adverse effects (nausea, vomiting, diarrhea) appear.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/19/2023 (0)
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