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Cephalexin Monohydrate

Antimicrobial Agents
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Keflex, Biocef


Suspension: 125 mg/5mL
Capsules: 250 mg, and 500 mg (cephalexin monohydrate)


A first generation cephalosporin, cephalexin is a broad-spectrum, bactericidal antibiotic. It is effective against most Gram-positive organisms such as beta-hemalytic streptococci, Staphylococcus intermedius and aureus, Proteus mirabili, some E. coli, klebsiella, actinobacillis, pasturella, and salmonella. It, however, does not directly attack mycoplasma, but is useful in secondary infections.

The drug is well absorbed orally, and widely distributed throughout the body. It crosses both placental and fetal serum, and is not recommended during pregnancy. It does not enter cerebral spinal fluid in appreciable levels. It also does not show significant levels in breast milk, and may be given to lactating females.

The drug is excreted by the kidneys via tubular and or glomerulo secretion.


Used for treating deep skin (pyodermas), soft tissue, and urinary tract infections. Also good for use prophylactically following surgery to prevent infection.

Drug Interactions or Contraindications

Should not be used orally in cases of septicemia or shock as absorption may be delayed significantly in grave illness.

Use cautiously with aminoglycosides. May have synergistic effect against certain bacteria, when used with the aminoglycosides, penicillins, and chloramphenicol. Not recommended for concurrent use with bacteriostatics.

Adverse Reactions

Blood:  neutopenia, hemolytic anemia

GI:  anorexia(poor or no appetite), diarrhea, anal pruritus(itching)

Other:  potential for nephrotoxicity minimal in animals.

Dosage Recommendations

60 mg/kg PO   7


60 mg/kg, PO, q12hrs, or 15 mg/kg, SQ, q12hrs   8  19


15 mg/kg, SQ, q12hrs   31 34 35


15 mg/kg, SQ, q24hrs.  34


  • Can be used simultaneously with Gentocin.
  • Give yogurt, Lactobacillus capsules/granules, or Bene-Bac to help maintain normal gut flora.
  • May store tablets and capsules at room temperature.
  • Reconstituted suspensions kept refrigerated are good for 14 days.
  • Considered safe for long term use.
  • In treating suspected polymicrobial infections, where a broader coverage may be needed, synergistic or combination drugs may be used. The following drugs may be seen used simultaneously with cephalexin: aminoglycosides (e.g., amikacin or gentamicin), or clindamycin, or fluoroquinolones (e.g., enrofloxacin or orbifloxicin), or metronidazole, or ampicillin . 1
  • Please note that it is imperative to discuss the changing or adding of any medications during your rat’s treatment with your veterinarian to prevent future resistance of microbes to the drugs prescribed.

Posted on June 23, 2003, 14:21, Last updated on September 10, 2016, 13:39 | Antimicrobial Agents

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