Cephalexin
Cephalexin is a generic medication for the drug Keflex Pulvules:
Cephalexin medication comes in several different strengths; click on the strength you need to view prices from pharmacies competing to earn your business.
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Cephalexin 250 mg
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Cephalexin 500 mg
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Pharmacology
Pharmacokinetics
Cephalexin is completely absorbed after oral administration. Following single doses of 250 mg, 500 mg or 1 g, in healthy, fasting adults, peak serum concentrations of 9 µg/mL, 18 µg/mL or 32 µg/mL occur within 1 hour, respectively. Less than 10% of absorbed drug is bound to serum protein. The half-life of cephalexin in adults with normal renal function ranges from 0.5 to 1.2 hours. In adults with end-stage renal disease, the half-life is prolonged (~16 hours). More than 80% is excreted as cephalexin in the urine, through glomerular filtration and tubular secretion.
Cephalexin is acid-stable. Food in the stomach causes a delay in onset and a lower peak concentration but does not decrease the total amount of cephalexin absorbed. Concomitant probenecid prolongs the half-life of cephalexin.
Indications
Cephalexin is used in the following clinical settings to treat or prevent infections caused by susceptible organisms:
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Treatment of uncomplicated skin and soft-tissue bacterial infections, including impetigo, carbuncles and cellulitis, caused by gram-positive organisms. Re-evaluate patients 24 to 48 hours after receiving the cephalexin [Clin Infect Dis 2005;41(10):1373-406].
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Treatment of postpartum breast abscess or mastitis.
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Treatment of septic bursitis.
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Treatment of group A streptococcal pharyngitis. Penicillin V is the recommended drug of choice for the treatment of group A streptococcal pharyngitis. Cephalexin is used as an alternative in penicillin-allergic patients who are not considered to be at risk of immediate hypersensitivity reactions [Clin Infect Dis 2002;35(2):113-25].
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Treatment of asymptomatic bacteriuria in pregnancy. Also used in traumatic pre-operative genitourinary procedures involving mucosal bleeding [Clin Infect Dis 2005;40(5):643-54].
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Treatment of acute cystitis in pregnant women [Anti-infective Review Panel. Anti-infective guidelines for community-acquired infections. Toronto (ON): MUMS Guideline Clearinghouse; 2005].
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Oral step-down treatment of acute osteomyelitis after initial iv therapy for MSSA once the patient's condition has stabilized.
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Prevention of infective endocarditis in susceptible patients. Oral amoxicillin is preferred; however, oral cephalexin is recommended as an oral alternative in penicillin-allergic patients who are not considered to be at risk of immediate hypersensitivity reactions [Circulation 2007;116(15):1736-54].
Patients with any of the following conditions may benefit from cephalexin for prevention of infective endocarditis while undergoing certain dental or surgical procedures so as to prevent severe outcomes: prosthetic heart valves or prosthetic material used for the cardiac valve region, previous infective endocarditis, heart transplantation recipients who develop cardiac valvulopathy, congenital heart disease, i.e., unrepaired cyanotic congenital heart disease, including palliative shunts and conduits; repaired congenital heart disease with residual effects at the site or adjacent to the site of a prosthetic patch or prosthetic device which inhibits endothelialization; completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first six months after the procedure [Circulation 2007;116(15):1736-54]. Antibiotic prophylaxis against infective endocarditis is recommended in the aforementioned patients for dental procedures that involve manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa, procedures on respiratory tract involving incision or biopsy of respiratory mucosa and procedures in patients with infected skin, skin structures or musculoskeletal tissue; however, antibiotic prophylaxis against infective endocarditis is not recommended for genitourinary or gastrointestinal tract procedures [Circulation 2007;116(15):1736-54].
Cephalexin is no longer recommended for the treatment of animal bites because of poor in vitro activity against P. multocida. Cephalexin is no longer recommended for the treatment of human bites because of resistance of E. corrodens, a prominent aerobic pathogen, to first-generation cephalosporins [Clin Infect Dis 2005;41(10):1373-406].
Precautions
See Warnings and Precautions.
Warnings and Precautions
Renal
Nephrotoxicity has been reported rarely with cephalosporins, and is more likely in older individuals, or in patients who are taking other nephrotoxic drugs concomitantly or have pre-existing renal impairment. Since cephalexin is renally cleared, dose adjustment is recommended in patients with impaired renal function (see Table 4).
Special Populations
Hematologic
Rarely, mild, transient neutropenia and other blood dyscrasias have occurred with cephalosporins.
Cephalexin
Drug Interactions
| Interacting Drug | Effect | Clinical Comment |
|---|---|---|
| Probenecid | Probenecid inhibits renal tubular excretion of cephalexin, which may result in decreased elimination of cephalexin. | This interaction has been exploited to increase serum levels of penicillins and most cephalosporins. |
Pregnant Women
Pregnancy Category BM. Although it has not been unequivocally established that there is not an increased risk of birth defects with the use of cephalexin, it is generally accepted that cephalosporins are safe to use during pregnancy.
Nursing Women
Cephalexin is excreted in breast milk in low concentrations. Potential risks to the infant include altered bowel flora, diarrhea, obscured diagnosis of fever and hypersensitivity reactions. Cephalosporins are generally considered to be compatible with breast-feeding.
Hepatic
Transient elevation of liver enzymes (AST and ALT) has occurred rarely during cephalosporin therapy.
Drug/Laboratory Test Interactions
Cephalexin may produce a false positive reaction for glucose in the urine with Benedict or Fehling's solution or with Clinitest tablets, but not with Tes-Tape (Glucose Enzymatic Test Strip, USP).
Positive direct Coombs' tests have been reported during treatment with the cephalosporins. This can interfere with cross-matching for transfusion, hematologic studies or Coombs' testing of neonates whose mothers received a cephalosporin prior to delivery.
Contraindications
Patients who are hypersensitive to cephalexin or to any ingredient in the formulation.
Patients who are hypersensitive to cephalosporins or to other β-lactam antibiotics.
Adverse Effects
Renal
interstitial nephritis, acute tubular necrosis.
Hematologic
eosinophilia, hemolytic anemia, neutropenia, thrombocytopenia.
Immune
serum sickness-like reaction.
Hepatic
cholestatic jaundice (rare), transient hepatitis (rare).
Overdose
For management of a suspected drug overdose, CPhA recommends that you contact your regional Poison Control Centre. See the eCPS Directories section for a list of Poison Control Centres.
Dosage
Cephalexin
Dose in Adult Patients with Renal Impairment
| Creatinine Clearance | Recommended Dosing Interval |
|---|---|
| >50 mL/min | Q6–8H |
| 10–50 mL/min | Q8–12H |
| <10 mL/min | Q12–24H |
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