displayName: DESCRIPTION SECTION
FDA Article Code: 34089-3
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:
The nucleus of cephalexin is related to that of other cephalosporin antibiotics. The compound is a zwitterion; i.e., the molecule contains both a basic and an acidic group. The isoelectric point of cephalexin in water is approximately 4.5 to 5.
The crystalline form of cephalexin which is available is a monohydrate. It is a white crystalline solid having a bitter taste. Solubility in water is low at room temperature; 1 or 2 mg/mL may be dissolved readily, but higher concentrations are obtained with increasing difficulty.
The cephalosporins differ from penicillins in the structure of the bicyclic ring system. Cephalexin has a D-phenylglycyl group as substituent at the 7-amino position and an unsubstituted methyl group at the 3-position.
Each capsule contains cephalexin USP equivalent to 250 mg or 500 mg of anhydrous cephalexin. The capsules also contain the following inactive ingredients D&C Yellow 10, edible printing ink with black iron oxide, FD&C Blue 1, FD&C Green 3, FD&C Yellow 6, gelatin, magnesium stearate, microcrystalline cellulose and titanium dioxide.
INDICATIONS AND USAGE
displayName: INDICATIONS & USAGE SECTION
FDA Article Code: 34067-9
Cephalexin is 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 Streptococcus pyogenes. (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 capsules 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.
displayName: CONTRAINDICATIONS SECTION
FDA Article Code: 34070-3
Cephalexin is contraindicated in patients with known allergy to the cephalosporin group of antibiotics.
displayName: WARNINGS SECTION
FDA Article Code: 34071-1
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.
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.
displayName: ADVERSE REACTIONS SECTION
FDA Article Code: 34084-4
Onset of pseudomembranous colitis may occur during or after antibacterial treatment. (See
) 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.
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:
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
). If seizures associated with drug therapy should occur, the drug should be discontinued. Anticonvulsant therapy can be given if clinically indicated.
Altered Laboratory Tests:
Prolonged prothrombin time, increased BUN, increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated LDH, pancytopenia, leukopenia, and agranulocytosis.
displayName: OVERDOSAGE SECTION
FDA Article Code: 34088-5
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.
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 stablished 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 >5,000 mg/kg.
DOSAGE AND ADMINISTRATION
displayName: DOSAGE & ADMINISTRATION SECTION
FDA Article Code: 34068-7
Cephalexin is administered orally.
The adult dosage ranges from 1 to 4 g daily in divided doses. 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.
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 ß-hemolytic streptococcal infections, a therapeutic dosage of cephalexin should be administered for at least 10 days.
displayName: HOW SUPPLIED SECTION
FDA Article Code: 34069-5
Cephalexin capsules USP 250 mg, 500 mg (or cephalexin, USP), are available in:
The 250 mg capsules are a white to yellowish-white granular powder filled into size “2” capsules (white and dark green) that are imprinted with “250” on dark green cap, and “LUPIN” on the white body in edible black ink. They are available as follows:
Bottles of 100 NDC 68180-121-01
Bottles of 500 NDC 68180-121-02
The 500 mg capsules are a white to yellowish-white granular powder filled into size “0” capsules (light green and dark green) that are imprinted with “500” on the dark green cap, and “LUPIN” on the light green body in edible black ink. They are available as follows:
Bottles of 100 NDC 68180-122-01
Bottles of 500 NDC 68180-122-02
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
displayName: REFERENCES SECTION
FDA Article Code: 34093-5
1. National Committee for Clinical Laboratory Standards. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically — Fourth Edition. Approved Standard NCCLS Document M7-A4, Vol. 17, No. 2, NCCLS, Wayne, PA, January, 1997.
National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Disk Susceptibility Tests — Sixth Edition. Approved Standard NCCLS Document M2-A6, Vol. 17, No. 1, NCCLS, Wayne, PA, January, 1997.
National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Susceptibility Testing — Eighth Informational Supplement. Approved Standard NCCLS Document M100-S8, Vol. 18, No. 1, NCCLS, Wayne, PA, January, 1998.