• Type: Beta lactamase resistant penicillins
  • Dosage Forms: 125mg/5 ml oral powder, 250mg, 500mg
  • Common Trade Names: Cloxapen, Dry Clox, Tegopen

Adult Dosing

Upper Respiratory Tract Infection

  • 250mg PO q6hrs for 7-14 days


  • 500mg PO q6hrs for up to 21 days

Soft tissue/skin infection

  • 500mg PO q6hrs for 7 days or until 3 days after acute inflammation resolves

Pediatric Dosing

Upper Respiratory Tract Infection

  • >=1 yr to 18 yrs: 50-100mg/kg/day orally divided every 6 hrs, Max dose 4g/day

Soft tissue and skin infection

  • >=1 yr to 18 yrs: 50-100mg/kg/day orally divided every 6 hrs, Max dose 4g/day

Special Populations

  • Pregnancy Rating: Pregnancy Category B
  • Lactation: acceptable to use during breastfeeding
  • Renal Dosing: no adjustments needed
  • Hepatic Dosing: no adjustments needed


  • Allergy to class/drug

Adverse Reactions


  • allergic reaction
  • seizures
  • pseudomembranous colitis
  • neutropenia
  • leukopenia
  • thrombocytopenia
  • cholestatic hepatitis
  • hypersensitivity reaction


  • nausea, vomiting
  • diarrhea, abdominal pain
  • thrush/yeast infection


  • Half-life: 30 min - 1 hr
  • Metabolism: partially metabolized
  • Excretion: renal and biliary
  • Mechanism of Action: bactericidal; adheres to penicillin-binding proteins inhibiting bacterial cell wall synthesis

Antibiotic Sensitivities[1]

Group Organism Sensitivity
Gram Positive Strep. Group A, B, C, G S
Strep. Pneumoniae S
Viridans strep I
Strep. anginosus gp S
Enterococcus faecalis R
Enterococcus faecium R
Staph. Epidermidis S
C. jeikeium R
L. monocytogenes R
Gram Negatives N. gonorrhoeae R
N. meningitidis R
Moraxella catarrhalis R
H. influenzae R
E. coli R
Klebsiella sp R
E. coli/Klebsiella ESBL+ R
E coli/Klebsiella KPC+ R
Enterobacter sp, AmpC neg R
Enterobacter sp, AmpC pos R
Serratia sp R
Serratia marcescens X1
Salmonella sp R
Shigella sp R
Proteus mirabilis R
Proteus vulgaris R
Providencia sp. R
Morganella sp. R
Citrobacter freundii R
Citrobacter diversus R
Citrobacter sp. R
Aeromonas sp R
Acinetobacter sp. R
Pseudomonas aeruginosa R
Burkholderia cepacia R
Stenotrophomonas maltophilia R
Yersinia enterocolitica R
Francisella tularensis X1
Brucella sp. X1
Legionella sp. R
Pasteurella multocida R
Haemophilus ducreyi X1
Vibrio vulnificus X1
Misc Chlamydophila sp R
Mycoplasm pneumoniae R
Rickettsia sp X1
Mycobacterium avium X1
Anaerobes Actinomyces R
Bacteroides fragilis R
Prevotella melaninogenica R
Clostridium difficile X1
Clostridium (not difficile) X1
Fusobacterium necrophorum X1
Peptostreptococcus sp. S


  • S susceptible/sensitive (usually)
  • I intermediate (variably susceptible/resistant)
  • R resistant (or not effective clinically)
  • S+ synergistic with cell wall antibiotics
  • U sensitive for UTI only (non systemic infection)
  • X1 no data
  • X2 active in vitro, but not used clinically
  • X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
  • X4 active in vitro, but not clinically effective for strep pneumonia

See Also


  1. Sanford Guide to Antimicrobial Therapy 2014