Cefalexin

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Cefalexin
Adult Indications & Dosage
Pediatric Indications & Dosage
Contraindications
Warnings & Precautions
Adverse Reactions
Drug Interactions
Use in Specific Populations
Administration & Monitoring
Overdosage
Pharmacology
Clinical Studies
How Supplied
Images
Patient Counseling Information
Precautions with Alcohol
Brand Names
Look-Alike Names

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Adeel Jamil, M.D. [2]

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Overview

Cefalexin is a {{{drugClass}}} that is FDA approved for the treatment of infections of respiratory tract, nasopharynx, otitis media, skin and skin structure and genitourinary tract infections including acute prostatitis.. Common adverse reactions include diarrhea, dyspepsia, gastritis, and abdominal pain, rash, dizziness, fatigue and headache..

Adult Indications and Dosage

FDA-Labeled Indications and Dosage (Adult)

Cephalexin capsules are indicated for the treatment of the following infections when caused by susceptible strains of the designated microorganisms:

Respiratory tract infections caused by Streptococcus pneumoniae and (Penicillin is the usual drug of choice in the treatment and prevention of streptococcal infections, including the prophylaxis of rheumatic fever. Cephalexin is generally effective in the eradication of streptococci from the nasopharynx; however, substantial data establishing the efficacy of cephalexin in the subsequent prevention of rheumatic fever are not available at present.)

Otitis media due to Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Streptococcus pyogenes, and Moraxella catarrhalis

Skin and skin structure infections caused by Staphylococcus aureus and/or Streptococcus pyogenes

Bone infections caused by Staphylococcus aureus and/or Proteus mirabilis

Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae

Note: Culture and susceptibility tests should be initiated prior to and during therapy. Renal function studies should be performed when indicated.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of cephalexin and other antibacterial drugs, cephalexin capsules should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Dosing Information

Cephalexin capsules are administered orally.

Adults — The adult dosage ranges from 1 to 4 g daily in divided doses. The 333 mg and the 750 mg strengths should be administered such that the daily dose is within 1 to 4 grams per day. The usual adult dose is 250 mg every 6 hours. For the following infections, a dosage of 500 mg may be administered every 12 hours: streptococcal pharyngitis, skin and skin structure infections, and uncomplicated cystitis in patients over 15 years of age. Cystitis therapy should be continued for 7 to 14 days. For more severe infections or those caused by less susceptible organisms, larger doses may be needed. If daily doses of cephalexin greater than 4 g are required, parenteral cephalosporins, in appropriate doses, should be considered.

Off-Label Use and Dosage (Adult)

Guideline-Supported Use

Bacterial endocarditis; Prophylaxis

Non–Guideline-Supported Use

Condition1
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Non–Guideline-Supported Use of Cefalexin in adult patients.

Pediatric Indications and Dosage

FDA-Labeled Indications and Dosage (Pediatric)

Pediatric Patients — The usual recommended daily dosage for pediatric patients is 25 to 50 mg/kg in divided doses. For streptococcal pharyngitis in patients over 1 year of age and for skin and skin structure infections, the total daily dose may be divided and administered every 12 hours.

In severe infections, the dosage may be doubled.

In the therapy of otitis media, clinical studies have shown that a dosage of 75 to 100 mg/kg/day in 4 divided doses is required.

In the treatment of β-hemolytic streptococcal infections, a therapeutic dosage of cephalexin should be administered for at least 10 days.

Off-Label Use and Dosage (Pediatric)

Guideline-Supported Use

Condition1
  • Developed by:
  • Class of Recommendation:
  • Strength of Evidence:
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Guideline-Supported Use of Cefalexin in pediatric patients.

Non–Guideline-Supported Use

Condition1
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Non–Guideline-Supported Use of Cefalexin in pediatric patients.

Contraindications

Cephalexin capsules are contraindicated in patients with known allergy to the cephalosporin group of antibiotics.

Warnings

Before therapy with cephalexin is instituted, careful inquiry should be made to determine whether the patient has had previous hypersensitivity reactions to cephalexin, cephalosporins, penicillins, or other drugs. If this product is to be given to penicillin-sensitive patients, caution should be exercised because cross-hypersensitivity among beta-lactam antibiotics has been clearly documented and may occur in up to 10% of patients with a history of penicillin allergy. If an allergic reaction to cephalexin occurs, discontinue the drug. Serious acute hypersensitivity reactions may require treatment with epinephrine and other emergency measures, including oxygen, intravenous fluids, intravenous antihistamines, corticosteroids, pressor amines and airway management, as clinically indicated.

There is some clinical and laboratory evidence of partial cross-allergenicity of the penicillins and the cephalosporins. Patients have been reported to have had severe reactions (including anaphylaxis) to both drugs.

Any patient who has demonstrated some form of allergy, particularly to drugs, should receive antibiotics cautiously. No exception should be made with regard to cephalexin capsules.

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including cephalexin, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C.difficile, and surgical evaluation should be instituted as clinically indicated.

Adverse Reactions

Clinical Trials Experience

Gastrointestinal — Onset of pseudomembranous colitis may occur during or after antibacterial treatment (See WARNINGS section). Nausea and vomiting have been reported rarely. The most frequent side effect has been diarrhea. It was very rarely severe enough to warrant cessation of therapy. Dyspepsia, gastritis, and abdominal pain have also occurred. As with some penicillins and some other cephalosporins, transient hepatitis and cholestatic jaundice have been reported rarely.

Hypersensitivity — Allergic reactions in the form of rash, urticaria, angioedema, and, rarely, erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis have been observed. These reactions usually subsided upon discontinuation of the drug. In some of these reactions, supportive therapy may be necessary. Anaphylaxis has also been reported.

Other reactions have included genital and anal pruritus, genital moniliasis, vaginitis and vaginal discharge, dizziness, fatigue, headache, agitation, confusion, hallucinations, arthralgia, arthritis, and joint disorder. Reversible interstitial nephritis has been reported rarely. Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia, and slight elevations in AST and ALT have been reported.

In addition to the adverse reactions listed above that have been observed in patients treated with cephalexin, the following adverse reactions and altered laboratory tests have been reported for cephalosporin class antibiotics:

Adverse Reactions — Fever, colitis, aplastic anemia, hemorrhage, renal dysfunction, and toxic nephropathy.

Several cephalosporins have been implicated in triggering seizures, particularly in patients with renal impairment when the dosage was not reduced (see INDICATIONS AND USAGE and PRECAUTIONS, GENERAL section). If seizures associated with drug therapy should occur, the drug should be discontinued. Anticonvulsant therapy can be given if clinically indicated.

Altered LaboratoryTests — Prolonged prothrombin time, increased BUN, increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated LDH, pancytopenia, leukopenia, and agranulocytosis.

Body as a Whole
Cardiovascular
Digestive
Endocrine
Hematologic and Lymphatic
Metabolic and Nutritional
Musculoskeletal
Neurologic
Respiratory
Skin and Hypersensitivy Reactions
Special Senses
Urogenital
Miscellaneous

Postmarketing Experience

There is limited information regarding Postmarketing Experience of Cefalexin in the drug label.

Body as a Whole
Cardiovascular
Digestive
Endocrine
Hematologic and Lymphatic
Metabolic and Nutritional
Musculoskeletal
Neurologic
Respiratory
Skin and Hypersensitivy Reactions
Special Senses
Urogenital
Miscellaneous

Drug Interactions

Metformin — In healthy subjects given single 500 mg doses of cephalexin and metformin, plasma metformin mean Cmax and AUC increased by an average of 34% and 24%, respectively, and metformin mean renal clearance decreased by 14%. No information is available about the interaction of cephalexin and metformin following multiple doses of either drug.

Although not observed in this study, adverse effects could potentially arise from coadministration of cephalexin and metformin by inhibition of tubular secretion via organic cationic transporter systems. Accordingly, careful patient monitoring and dose adjustment of metformin is recommended in patients concomitantly taking cephalexin and metformin.

Probenecid — As with other β-lactams, the renal excretion of cephalexin is inhibited by probenecid.

Drug / Laboratory Test Interactions As a result of administration of cephalexin capsules, a false-positive reaction for glucose in the urine may occur. This has been observed with Benedict’s and Fehling’s solutions and also with Clinitest® tablets.

Use in Specific Populations

Pregnancy

Pregnancy Category (FDA): B Teratogenic effects — Pregnancy Category B — Reproduction studies have been performed on mice and rats using oral doses of cephalexin monohydrate 0.6 and 1.5 times the maximum daily human dose (66 mg/kg/day) based upon mg/m2, and have revealed no harm to the fetus. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
Pregnancy Category (AUS):

  • Australian Drug Evaluation Committee (ADEC) Pregnancy Category

There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Cefalexin in women who are pregnant.

Labor and Delivery

There is no FDA guidance on use of Cefalexin during labor and delivery.

Nursing Mothers

The excretion of cephalexin in human milk increased up to 4 hours after a 500 mg dose; the drug reached a maximum level of 4 µg/mL, then decreased gradually, and had disappeared 8 hours after administration. Caution should be exercised when cephalexin capsule is administered to a nursing woman.

Pediatric Use

The safety and effectiveness of cephalexin in pediatric patients was established in clinical trials for the dosages described in the DOSAGE AND ADMINISTRATION section. In these trials, pediatric patients may have received cephalexin capsules or cephalexin for oral suspension. Cephalexin capsules should only be used in children and adolescents capable of ingesting the capsule.

Geriatic Use

Of the 701 subjects in 3 published clinical studies of cephalexin, 433 (62%) were 65 and over. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function (see PRECAUTIONS, GENERAL section).

Gender

There is no FDA guidance on the use of Cefalexin with respect to specific gender populations.

Race

There is no FDA guidance on the use of Cefalexin with respect to specific racial populations.

Renal Impairment

There is no FDA guidance on the use of Cefalexin in patients with renal impairment.

Hepatic Impairment

There is no FDA guidance on the use of Cefalexin in patients with hepatic impairment.

Females of Reproductive Potential and Males

There is no FDA guidance on the use of Cefalexin in women of reproductive potentials and males.

Immunocompromised Patients

There is no FDA guidance one the use of Cefalexin in patients who are immunocompromised.

Administration and Monitoring

Administration

  • Oral
  • Intravenous

Monitoring

There is limited information regarding Monitoring of Cefalexin in the drug label.

  • Description

IV Compatibility

There is limited information regarding IV Compatibility of Cefalexin in the drug label.

Overdosage

Signs and Symptoms — Symptoms of oral overdose may include nausea, vomiting, epigastric distress, diarrhea, and hematuria. If other symptoms are present, it is probably secondary to an underlying disease state, an allergic reaction, or toxicity due to ingestion of a second medication.

Treatment — To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. Telephone numbers of certified poison control centers are listed in the Physicians’ Desk Reference (PDR). In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in your patient.

Unless 5 to 10 times the normal dose of cephalexin has been ingested, gastrointestinal decontamination should not be necessary.

Protect the patient’s airway and support ventilation and perfusion. Meticulously monitor and maintain, within acceptable limits, the patient’s vital signs, blood gases, serum electrolytes, etc. Absorption of drugs from the gastrointestinal tract may be decreased by giving activated charcoal, which, in many cases, is more effective than emesis or lavage; consider charcoal instead of or in addition to gastric emptying. Repeated doses of charcoal over time may hasten elimination of some drugs that have been absorbed. Safeguard the patient’s airway when employing gastric emptying or charcoal.

Forced diuresis, peritoneal dialysis, hemodialysis, or charcoal hemoperfusion have not been established as beneficial for an overdose of cephalexin; however, it would be extremely unlikely that one of these procedures would be indicated.

The oral median lethal dose of cephalexin in rats is >5000 mg/kg.

Pharmacology

There is limited information regarding Cefalexin Pharmacology in the drug label.

Mechanism of Action

Structure

  • Cephalexin, USP is a semisynthetic cephalosporin antibiotic intended for oral administration. It is 7-(D-α-Amino-α-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid monohydrate. Cephalexin has the molecular formula C16H17N3O4S H2O and the molecular weight is 365.41.

Cephalexin has the following structural formula:

File:Cefalexin01.png
This image is provided by the National Library of Medicine.

Pharmacodynamics

There is limited information regarding Pharmacodynamics of Cefalexin in the drug label.

Pharmacokinetics

There is limited information regarding Pharmacokinetics of Cefalexin in the drug label.

Nonclinical Toxicology

There is limited information regarding Nonclinical Toxicology of Cefalexin in the drug label.

Clinical Studies

Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis, Mutagenesis, Impairment of Fertility

Lifetime studies in animals have not been performed to evaluate the carcinogenic potential of cephalexin. Tests to determine the mutagenic potential of cephalexin have not been performed. In male and female rats, fertility and reproductive performance were not affected by cephalexin oral doses up to 1.5 times the highest recommended human dose based upon mg/m2.

How Supplied

Cephalexin capsules, USP are available in:

The 250 mg capsules are a white to off white powder filled into size 2 capsules (white opaque cap and white opaque body) that are imprinted with 801 on the cap in black. They are available as follows:

Bottles of 100 NDC 15749-801-02

Bottles of 500 NDC 15749-801-08

The 500 mg capsules are a white to off white powder filled into size 0 capsules (white opaque cap and white opaque body) that are imprinted with 802 on the cap in black. They are available as follows:

Bottles of 100 NDC 15749-802-02

Bottles of 500 NDC 15749-802-08

Storage

Store at 20°C to 25°C (68°F to 77°F) [

Images

Drug Images

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This pill image is provided by the National Library of Medicine's PillBox.

Package and Label Display Panel

This image of the FDA label is provided by the National Library of Medicine.

Patient Counseling Information

Patients should be counseled that antibacterial drugs including cephalexin should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When cephalexin is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by cephalexin or other antibacterial drugs in the future.

Diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic. If this occurs, patients should contact their physician as soon as possible.

Precautions with Alcohol

  • Alcohol-Cefalexin interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

Brand Names

Look-Alike Drug Names

Drug Shortage Status

Price

References

The contents of this FDA label are provided by the National Library of Medicine.

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