Cephalexin
Pronouncation: (seh-fuh-LEX-in)
Class: Antibiotic, Cephalosporin
Trade Names:
Biocef
- Powder for Oral Suspension 125 mg/5 mL
- Powder for Oral Suspension 250 mg/5 mL
Trade Names:
Keflex
- Capsules 250 mg
- Capsules 500 mg
- Powder for Oral Suspension 125 mg/5 mL
- Powder for Oral Suspension 250 mg/5 mL
Trade Names:
Keftab
- Tablets 500 mg (as hydrochloride monohydrate)
APO-Cephalex (Canada)
Novo-Lexin (Canada)
Nu-Cephalex (Canada)
Mechanism of Action
Pharmacology
Inhibits mucopeptide synthesis in bacterial cell wall.
Pharmacokinetics
Absorption
Cephalexin is rapidly absorbed. C max is about 9 to 32 mcg/mL (250 mg to 1 g doses). T max is 1 h.
Distribution
Cephalexin is 10% protein bound.
Elimination
More than 90% is excreted unchanged in the urine within 8 h. The t ½ is 50 to 80 min.
Indications and Usage
Treatment of infections of respiratory tract, urinary tract, skin and skin structures and bone; treatment of otitis media caused by susceptible strains of specific microorganisms.
Contraindications
Hypersensitivity to cephalosporins.
Dosage and Administration
Adults
PO 1 to 4 g/day in divided doses (max, 4 g/day).
Children
PO (cephalexin monohydrate only) 25 to 100 mg/kg/day in divided doses.
General Advice
- Administer with food or milk if GI upset occurs. Food slows but does not decrease absorption.
- Shake oral suspension well before measuring and administering. Space doses evenly around clock.
Storage/Stability
Oral suspension is stable up to 14 days after reconstitution when refrigerated. Store capsules and tablets at room temperature.
Drug Interactions
Probenecid
Inhibition of renal excretion of cephalexin.
Laboratory Test Interactions
May cause false-positive urine glucose test results with Benedict solution, Fehling solution, or Clinitest tablets but not with enzyme-based tests (eg, Clinistix , Tes-tape ); false-positive test results for proteinuria with acid and denaturization-precipitation tests; false-positive direct Coombs test results in certain patients (eg, those with azotemia); false elevations in urinary 17-ketosteroid values.
Adverse Reactions
GI
Nausea; vomiting; diarrhea; anorexia; abdominal pain or cramps; flatulence; colitis, including pseudomembranous colitis.
Genitourinary
Pyuria; renal function impairment; dysuria; reversible interstitial nephritis; hematuria; toxic nephropathy.
Hematologic
Eosinophilia; neutropenia; lymphocytosis; leukocytosis; thrombocytopenia; decreased platelet function; anemia; aplastic anemia; hemorrhage.
Hepatic
Hepatic dysfunction; abnormal LFT results.
Miscellaneous
Hypersensitivity, including Stevens-Johnson syndrome, erythema multiforme, toxic epidermal necrolysis; candidal overgrowth; serum sickness–like reactions (eg, skin rash, polyarthritis, arthralgia, fever).
Precautions
Monitor
Response to therapy
Monitor patient's response to therapy. Notify health care provider if infection does not appear to improve or worsens.
Adverse reactions
Monitor patient for GI, DERM, and general body adverse reactions, and signs of superinfection. Inform health care provider if noted and significant. Immediately report severe diarrhea, diarrhea containing blood or pus, or severe abdominal cramping.
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Pregnancy
Category B .
Lactation
Excreted in breast milk.
Children
Safety and efficacy of cephalexin hydrochloride monohydrate ( Keftab ) in children not established. Cephalosporins may accumulate in newborns.
Hypersensitivity
Reactions range from mild to life-threatening. Administer drug with caution to penicillin-sensitive patients because of possible cross-reactivity.
Renal Function
Use drug with caution in patients with renal function impairment. Dosage adjustment based on renal function may be required.
Superinfection
May result in bacterial or fungal overgrowth of nonsusceptible microorganisms.
Pseudomembranous colitis
Consider in patients in whom diarrhea develops.
Overdosage
Symptoms
Seizures.
Patient Information
- Instruct patient to complete full course of therapy.
- Advise patient to take with food or milk if GI distress occurs.
- Remind patient to check body temperature daily. If fever persists for more than a few days or if high fever (greater than 102°F) or shaking chills are noted, notify health care provider immediately.
- Advise patient to maintain normal fluid intake while using this medication.
- Advise diabetic patient to use enzyme-based tests (eg, Clinistix , Testape ) for monitoring urine glucose because drug may give false results with other tests.
- Instruct patient to report these symptoms to health care provider: nausea, vomiting, diarrhea, skin rash, hives, muscle or joint pain.
- Instruct patient to report signs of superinfection: black “furry” tongue, white patches in mouth, foul-smelling stools, vaginal itching or discharge.
- Warn patient that diarrhea that contains blood or pus may be a sign of serious disorders. Tell patient to seek medical care and not to treat at home.
- Instruct patient to seek emergency care immediately if wheezing or difficulty breathing occurs.
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