Class: First Generation Cephalosporins
CAS Number: 23325-78-2
Brands: Keflex
Introduction
Antibacterial; β-lactam antibiotic; first generation cephalosporin.a
Uses for Cephalexin
Acute Otitis Media (AOM)
Treatment of AOM caused by susceptible S. pneumoniae, Haemophilus influenzae, M. catarrhalis, or staphylococci or streptococci.100 105 110 111
Pharyngitis and Tonsillitis
Treatment of pharyngitis and tonsillitis caused by Streptococcus pyogenes (group A β-hemolytic streptococci).100 105 110 111 Generally effective in eradicating S. pyogenes from the nasopharynx, but efficacy in prevention of subsequent rheumatic fever has not been established to date.100 105 110 111
CDC, AAP, IDSA, AHA, and others recommend oral penicillin V or IM penicillin G benzathine as treatments of choice;102 107 108 109 oral cephalosporins and oral macrolides considered alternatives.102 107 108 109 Amoxicillin sometimes used instead of penicillin V, especially for young children.102 107
Bone and Joint Infections
Treatment of bone and joint infections caused by susceptible staphylococci or Proteus mirabilis.100 105 110 111
Respiratory Tract Infections
Treatment of mild to moderate respiratory tract infections caused by Streptococcus pneumoniae.100 105 110 111
Skin and Skin Structure Infections
Treatment of mild to moderate skin and skin structure infections caused by susceptible staphylococci or streptococci.100 105 110 111
Urinary Tract Infections (UTIs)
Treatment of mild to moderate UTIs, including acute prostatitis, caused by susceptible Escherichia coli, Klebsiella pneumoniae, or P. mirabilis.100 105 110 111
Prevention of Bacterial Endocarditis
Alternative for prevention of α-hemolytic (viridans group) streptococcal endocarditis† in penicillin-allergic individuals undergoing certain dental or upper respiratory tract procedures who have cardiac conditions that put them at highest risk.104 Should not be used in those with immediate-type penicillin hypersensitivity (see Cross-hypersensitivity under Cautions).104
When selecting anti-infectives for prophylaxis of bacterial endocarditis, consult most recent AHA recommendations for specific information on which cardiac conditions are associated with highest risk of endocarditis and which procedures require prophylaxis.104
Cephalexin Dosage and Administration
Administration
Oral Administration
Administer orally without regard to meals.100 105 110 111
Reconstitution
Reconstitute oral suspension at time of dispensing by adding the amount of water specified on the container.105 111
Reconstituted suspensions contain 125 or 250 mg of cephalexin/5 mL.105 111
Shake oral suspension well prior to administration of each dose.105
Dosage
Available as cephalexin monohydrate; dosage expressed in terms of cephalexin.100 105 110 111
Pediatric Patients
General Pediatric Dosage
Oral
25–50 mg/kg daily in divided doses.100 102 110 111 Manufacturers state that these dosages may be doubled for severe infections;100 110 111 AAP states that cephalexin is inappropriate for severe infections.102
Acute Otitis Media (AOM)
Oral
75–100 mg/kg daily in 4 divided doses.100 105 110 111
Pharyngitis and Tonsillitis
Oral
25–50 mg/kg daily in 3–4 equally divided doses for ≥10 days.100 102 105 110 111 Daily dosage may be given in divided doses every 12 hours in those >1 year of age.100 105 110 111
Children >15 years of age: 500 mg every 12 hours for ≥10 days.100 105 110 111
Bone and Joint Infections
Oral
25–50 mg/kg daily in 3–4 equally divided doses for mild to moderate infections.100 102 105
Manufacturers state dosage may be doubled for severe infections;100 105 110 111 AAP states the drug is inappropriate for severe infections.102
Respiratory Tract Infections
Oral
25–50 mg/kg daily in 3–4 equally divided doses for mild to moderate infections.100 102 105
Manufacturers state dosage may be doubled for severe infections;100 105 AAP states the drug is inappropriate for severe infections.102
Skin and Skin Structure Infections
Oral
25–50 mg/kg daily in divided doses every 12 hours for mild to moderate infections.100 105 110 111
Children >15 years of age: 500 mg every 12 hours for mild to moderate infections.100 105 110 111
Manufacturers state dosage may be doubled for severe infections;100 105 110 111 AAP states the drug is inappropriate for severe infections.102
Urinary Tract Infections (UTIs)
Oral
25–50 mg/kg daily in 3–4 equally divided doses for mild to moderate infections.100 102 105
Children >15 years of age with uncomplicated cystitis: 500 mg every 12 hours for 7–14 days.100 105
Manufacturers state dosage may be doubled for severe infections;100 105 110 111 AAP states the drug is inappropriate for severe infections.102
Prevention of Bacterial Endocarditis†
Patients Undergoing Certain Dental or Upper Respiratory Tract Procedures†
Oral
50 mg/kg (up to 2 g) as a single dose given 0.5–1 hour prior to the procedure.104
Adults
General Adult Dosage
Oral
Usual dosage ranges from 1–4 g daily given in divided doses.100 105 If dosage >4 g daily is required, consider initial therapy with a parenteral cephalosporin.100 105
Acute Otitis Media (AOM)
Oral
250 mg every 6 hours.100 105 Higher dosage may be needed for severe infections or those caused by less susceptible bacteria.100 105
Pharyngitis and Tonsillitis
Oral
500 mg every 12 hours for ≥10 days.100 105 110 111
Bone and Joint Infections
Oral
250 mg every 6 hours.100 105 Higher dosage may be needed for severe infections or those caused by less susceptible bacteria.100 105
Respiratory Tract Infections
Oral
250 mg every 6 hours for mild to moderate infections.100 105 Higher dosage may be needed for more severe infections or those caused by less susceptible bacteria.100 105
Skin and Skin Structure Infections
Oral
500 mg every 12 hours for mild to moderate infections.100 105 110 111 Higher dosage may be needed for severe infections or those caused by less susceptible bacteria.100 105
Urinary Tract Infections (UTIs)
Oral
500 mg every 12 hours for 7–14 days for mild to moderate infections.100 105 110 111 Higher dosage may be needed for severe infections or those caused by less susceptible bacteria.100 105 110 111
Prevention of Bacterial Endocarditis†
Patients Undergoing Certain Dental or Upper Respiratory Tract Procedures†
Oral
2 g as a single dose given 0.5–1 hour prior to the procedure.104
Special Populations
Renal Impairment
Use with caution in patients with markedly impaired renal function; close clinical observation and appropriate laboratory tests recommended because safe dosage may be lower than usual dosages.100 105
Some clinicians suggest that the usual adult dosage be used for the initial dose.b Then, for subsequent doses, use 500 mg every 8–12 hours if Clcr 11–40 mL/minute, 250 mg every 12 hours if Clcr 5–10 mL/minute, or 250 mg every 12–24 hours if Clcr <5 mL/minute.b
Geriatric Patients
Cautious dosage selection because of age-related decreases in renal function.100 (See Renal Impairment under Dosage and Administration.)
Cautions for Cephalexin
Contraindications
Known hypersensitivity to cephalexin or other cephalosporins.100 105 110 111
Warnings/Precautions
Warnings
Superinfection/Clostridium difficile-associated Diarrhea and Colitis
Possible emergence and overgrowth of nonsusceptible bacteria or fungi with prolonged use.100 105 Careful observation of the patient is essential.100 105 Institute appropriate therapy if superinfection occurs.100 105
Treatment with anti-infectives may permit overgrowth of Clostridium difficile.100 105 C. difficile-associated diarrhea and colitis (CDAD; also known as antibiotic-associated diarrhea and colitis or pseudomembranous colitis) has been reported with nearly all anti-infectives, including cephalexin, and may range in severity from mild diarrhea to fatal colitis.100
Consider CDAD if diarrhea develops during or after therapy and manage accordingly.100 105 Careful medical history is necessary since CDAD has been reported to occur as late as 2 months or longer after anti-infective therapy is discontinued.100
If CDAD is suspected or confirmed, the anti-infective may need to be discontinued.100 105 Some mild cases may respond to discontinuance alone.100 105 a Manage moderate to severe cases with fluid, electrolyte, and protein supplementation, anti-infective therapy active against C. difficile (e.g., oral metronidazole or vancomycin), and surgical evaluation when clinically indicated.100 105 a
Sensitivity Reactions
Hypersensitivity Reactions
Possible hypersensitivity reactions (e.g., urticaria, pruritus, rash, fever and chills, eosinophilia, joint pain or inflammation, edema, erythema, genital and anal pruritus, angioedema, shock, hypotension, vasodilatation, Stevens-Johnson syndrome, erythema multiforme, toxic epidermal necrolysis, exfoliative dermatitis, anaphylaxis).100 105 110 111 a
If a hypersensitivity reaction occurs, discontinue cephalexin immediately and institute appropriate therapy as indicated (e.g., epinephrine, corticosteroids, maintenance of an adequate airway and oxygen).100 105 110 111 a
Cross-hypersensitivity
Partial cross-sensitivity among cephalosporins and other β-lactam antibiotics, including penicillins and cephamycins.100 105 110 111 a
Prior to initiation of therapy, make careful inquiry concerning previous hypersensitivity reactions to cephalosporins, penicillins, or other drugs.100 105 110 111 a Cautious use recommended in patients with a history of hypersensitivity to penicillins:100 105 110 111 avoid use in those who have had an immediate-type (anaphylactic) hypersensitivity reaction104 a and administer with caution in those who have had a delayed-type (e.g., rash, fever, eosinophilia) reaction.a
General Precautions
History of GI Disease
Cephalosporins should be used with caution in patients with a history of GI disease, particularly colitis.100 105 110 111 a (See Superinfection/Clostridium difficile-associated Diarrhea and Colitis under Cautions.)
Coombs' Test Results
Positive direct Coombs’ test results reported with cephalosporins.100 105 110 111 a This may interfere with certain hematologic studies or transfusion cross-matching procedures.100 105 110 111 a May also cause positive Coombs’ tests in neonates whose mothers received a cephalosporin prior to delivery.100 105 110 111 a
Selection and Use of Anti-infectives
To reduce development of drug-resistant bacteria and maintain effectiveness of cephalexin and other antibacterials, use only for treatment or prevention of infections proven or strongly suspected to be caused by susceptible bacteria.100
When selecting or modifying anti-infective therapy, use results of culture and in vitro susceptibility testing.100 In the absence of such data, consider local epidemiology and susceptibility patterns when selecting anti-infectives for empiric therapy.100
Specific Populations
Pregnancy
Category B.100 105
Lactation
Distributed into milk.100 105 Use with caution.100 105
Geriatric Use
No overall differences in safety and efficacy in adults ≥65 years of age compared with younger adults, but the possibility of increased sensitivity in some geriatric individuals cannot be ruled out.100
Substantially eliminated by kidneys; risk of toxicity may be greater in those with impaired renal function.100 Select dosage with caution and consider monitoring renal function because of age-related decreases in renal function.100 (See Renal Impairment under Dosage and Administration.)
Renal Impairment
Decreased clearance and increased plasma half-life.b
Use with caution in those with markedly impaired renal function;100 105 close clinical observation and appropriate laboratory tests recommended.100 105
Reduced dosage has been recommended in those with Clcr ≤ 40 mL/minute.a (See Renal Impairment under Dosage and Administration.)
Common Adverse Effects
Adverse GI effects, including diarrhea, nausea, vomiting, dyspepsia, gastritis, abdominal pain.100 105
Interactions for Cephalexin
Specific Drugs and Laboratory Tests
Drug or Test | Interaction | Comments |
---|---|---|
Metformin | Increased plasma concentrations and AUC and decreased renal clearance of metformin;100 potential for increased adverse effects associated with metformin | Monitor closely; adjust metformin dosage if necessary100 |
Probenecid | Decreased renal excretion and increased plasma concentrations of cephalexin100 105 | |
Tests for glucose | Possible false-positive reactions in urine glucose tests using Clinitest, Benedict’s solution, or Fehling’s solution100 105 a | Use glucose tests based on enzymatic glucose oxidase reactions (e.g., Clinistix, Tes-Tape)a |
Cephalexin Pharmacokinetics
Absorption
Bioavailability
Rapidly and completely absorbed from the GI tract.100 105 Peak serum concentrations within 1 hour.100 105
Food
Although peak serum concentrations are slightly lower and attained later when administered with food, total amount of drug absorbed is unchanged.b
Distribution
Extent
Cephalosporins widely distributed into tissues and fluids.a
Distributed into milk.100 105
Plasma Protein Binding
6–15%.a
Elimination
Metabolism
Not appreciably metabolized.a
Elimination Route
Excreted in urine as unchanged drug by renal tubular secretion and glomerular filtration.100 105
At least 70–90% of a dose eliminated in urine within 8–12 hours in adults with normal renal function.100 105 b
Half-life
Adults with normal renal function: 0.5–1.2 hours.b
Children: about 5 hours in neonates and 2.5 hours in children 3–12 months of age.b
Special Populations
Decreased clearance and increased half-life in patients with renal impairment.b Half-life is 7.7–13.9 in adults with Clcr <13.5 mL/minute.b
Stability
Storage
Oral
Capsules
25°C (may be exposed to 15–30°C).100 105
For Suspension
15–30°C in tight, light-resistant container.105 After reconstitution, refrigerate in a tight container for up to 14 days.105
Actions and SpectrumActions
First generation cephalosporin with a limited spectrum of activity compared with second and third generation cephalosporins.a
Usually bactericidal.100 105
Like other β-lactam antibiotics, antibacterial activity results from inhibition of bacterial cell wall synthesis.a
In vitro spectrum of activity includes some gram-positive aerobic bacteria and some gram-negative aerobic bacteria.100 105 a Inactive against anaerobic bacteria, fungi, and viruses.a
Gram-positive aerobes: active in vitro and in clinical infections against gram-positive aerobic bacteria including Staphylococcus aureus and S. epidermidis (including penicillinase-producing strains), Streptococcus pyogenes (group A β-hemolytic streptococci), and S. pneumoniae.100 105 a Oxacillin-resistant (methicillin-resistant) staphylococci and most enterococci are resistant.100 a
Gram-negative aerobes: active in vitro and in clinical infections against some gram-negative aerobic bacteria including Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis.100 105 a Inactive against Acinetobacter, Citrobacter, Enterobacter, Listeria monocytogenes, Morganella morganii, Providencia, Pseudomonas, and Serratia.100 105 a b
Advice to Patients
Advise patients that antibacterials (including cephalexin) should only be used to treat bacterial infections and not used to treat viral infections (e.g., the common cold).100
Importance of completing full course of therapy, even if feeling better after a few days.100
Advise patients that skipping doses or not completing the full course of therapy may decrease effectiveness and increase the likelihood that bacteria will develop resistance and will not be treatable with cephalexin or other antibacterials in the future.100
Advise patients that diarrhea is a common problem caused by anti-infectives and usually ends when the drug is discontinued.100 Importance of contacting a clinician if watery and bloody stools (with or without stomach cramps and fever) occur during or as late as 2 months or longer after the last dose.100
Importance of discontinuing therapy and informing clinician if an allergic reaction occurs.100
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs as well as any concomitant illnesses.100
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.
Importance of informing patients of other important precautionary information. (See Cautions.)
Preparations
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name
Routes | Dosage Forms | Strengths | Brand Names | Manufacturer |
---|---|---|---|---|
Oral | Capsules | 250 mg* | Cephalexin Capsules | Lupin, Ranbaxy, Teva, West-Ward |
Keflex | Middlebrook | |||
333 mg | Keflex | Middlebrook | ||
500 mg* | Cephalexin Capsules | Lupin, Ranbaxy, Teva, West-Ward | ||
Keflex | Middlebrook | |||
750 mg | Keflex | Middlebrook | ||
For suspension | 125 mg/5 mL* | Cephalexin for Suspension | Lupin, Ranbaxy, Teva | |
Keflex | Middlebrook | |||
250 mg/5 mL* | Cephalexin for Suspension | Lupin, Ranbaxy, Teva | ||
Keflex | Middlebrook | |||
Tablets, film-coated | 250 mg* | Cephalexin Film-coated Tablets | Teva | |
500 mg* | Cephalexin Film-coated Tablets | Teva |
Comparative Pricing
This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 03/2011. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.
Cephalexin 125MG/5ML Suspension (TEVA PHARMACEUTICALS USA): 100/$15.99 or 200/$21.98
Cephalexin 250MG Capsules (TEVA PHARMACEUTICALS USA): 30/$13.99 or 60/$17.98
Cephalexin 250MG/5ML Suspension (LUPIN PHARMACEUTICALS): 200/$22.99 or 600/$68.97
Cephalexin 250MG/5ML Suspension (TEVA PHARMACEUTICALS USA): 100/$16.99 or 200/$22.97
Keflex 500MG Capsules (VICTORY PHARMA): 30/$175.99 or 90/$514.95
Keflex 750MG Capsules (VICTORY PHARMA): 50/$215.98 or 150/$630
Disclaimer
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. and Drugs.com represent that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. and Drugs.com make no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. and Drugs.com do not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS Drug Information. © Copyright, 1959-2011, Selected Revisions February 2008. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.
† Use is not currently included in the labeling approved by the US Food and Drug Administration.
References
Only references cited for selected revisions after 1984 are available electronically.
100. Middlebrook. Keflex (cephalexin USP) capsules prescribing information. Germantown, MD. 2007 Jun.
102. American Academy of Pediatrics. 2006 Red Book: Report of the Committee on Infectious Diseases. 27th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2006:756,834.
103. Kamar A, Murray DL, Hanna CB et al. Comparative study of cephalexin hydrochloride and cephalexin monohydrate in the treatment of skin and soft tissue infections. Antimicrob Agents Chemother. 1988; 32:882-5. [IDIS 244249] [PubMed 3046484]
104. Wilson W, Taubert KA, Gewitz M et al. Prevention of infective endocarditis. Guidelines from the American Heart Association. A guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007 Apr 19. (Epub ahead of print).
105. Ranbaxy. Cephalexin capsules USP and cephalexin oral suspension USP prescribing information. Princeton, NJ; 2002 May.
107. Bisno AL, Gerber MA, Gwaltney JM et al et al. Diagnosis and management of group A streptococcal pharyngitis: a practice guideline. Clin Infect Dis. 1997; 25:574-83. [PubMed 9314443]
108. Dajani A, Taubert K, Ferrieri P et al and the American Heart Association Committee on Rheumatic Fever et al. Treatment of acute streptococcal pharyngitis and prevention of rheumatic fever: a statement for health professionals. Pediatrics. 1995; 96:758-64. [IDIS 355409] [PubMed 7567345]
109. Cooper RJ, Hoffman JR, Bartlett JG et al. Principles of appropriate antibiotic use for acute pharyngitis in adults: background. Ann Intern Med. 2001; 134:509-17. [IDIS 460578] [PubMed 11255530]
110. Lupin. Cephalexin capsules USP prescribing information. Baltimore, MD; 2005 Sep.
111. Lupin. Cephalexin for oral suspension USP prescribing information. Baltimore, MD; 2005 May.
112. Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing; sixteenth informational supplement. CLSI document M100-S16. Wayne, PA; 2006.
a. AHFS Drug Information 2003. McEvoy GK, ed. Cephalosporins General Statement. American Society of Health-System Pharmacists; 2003:125-39.
b. AHFS Drug Information 2003, McEvoy GK, ed. Cephalexin/ Cephalexin Hydrochloride. American Society of Health-System Pharmacists; 2003:231-2.
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