Cephalexin Information
Cephalexin ()
Cephalexin () Description
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 following structural formula:
CHNOS•HO M.W. 365.41
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 -phenylglycyl group as substituent at the 7-amino position and an unsubstituted methyl group at the 3-position.
Each capsule contains Cephalexin () monohydrate equivalent to 250 mg (720 μmol) or 500 mg (1,439 μmol) of Cephalexin () .
After mixing, each 5 mL of Cephalexin () for oral suspension USP will contain Cephalexin () monohydrate equivalent to 125 mg (360 μmol) or 250 mg (720 μmol) of Cephalexin () .
Each tablet contains Cephalexin () monohydrate equivalent to 250 mg (720 μmol) or 500 mg (1,439 μmol) of Cephalexin () .
Cephalexin () Clinical Pharmacology
Aerobes, Gram-positive:
Staphylococcus aureus
Streptococcus pneumoniae
Streptococcus pyogenes
Aerobes, Gram-negative:
Escherichia coli
Haemophilus influenzae
Klebsiella pneumoniae
Moraxella (Branhamella) catarrhalis
Proteus mirabilis
Cephalexin () Indications And Usage
Cephalexin () is indicated for the treatment of the following infections when caused by susceptible strains of the designated microorganisms:
Respiratory tract infections caused by 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 , , , and
Skin and skin structure infections caused by and/or
Bone infections caused by and/or
Genitourinary tract infections, including acute prostatitis, caused by and
To reduce the development of drug-resistant bacteria and maintain the effectiveness of Cephalexin () capsules, Cephalexin () for oral suspension, Cephalexin () tablets, and other antibacterial drugs, Cephalexin () capsules, Cephalexin () for oral suspension, and Cephalexin () tablets 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.
Cephalexin () Contraindications
Cephalexin () is contraindicated in patients with known allergy to the cephalosporin group of antibiotics.
Cephalexin () Warnings
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 () .
If CDAD is suspected or confirmed, ongoing antibiotic use not directed against may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of , and surgical evaluation should be instituted as clinically indicated.
Cephalexin () Precautions
Prescribing Cephalexin () capsules, Cephalexin () for oral suspension, or Cephalexin () tablets in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.
Patients should be followed carefully so that any side effects or unusual manifestations of drug idiosyncrasy may be detected. If an allergic reaction to Cephalexin () occurs, the drug should be discontinued and the patient treated with the usual agents (e.g., epinephrine or other pressor amines, antihistamines, or corticosteroids).
Prolonged use of Cephalexin () may result in the overgrowth of nonsusceptible organisms. Careful observation of the patient is essential. If superinfection occurs during therapy, appropriate measures should be taken.
Positive direct Coombs’ tests have been reported during treatment with the cephalosporin antibiotics. In hematologic studies or in transfusion cross-matching procedures when antiglobulin tests are performed on the minor side or in Coombs’ testing of newborns whose mothers have received cephalosporin antibiotics before parturition, it should be recognized that a positive Coombs’ test may be due to the drug.
Cephalexin () should be administered with caution in the presence of markedly impaired renal function. Under such conditions, careful clinical observation and laboratory studies should be made because safe dosage may be lower than that usually recommended.
Indicated surgical procedures should be performed in conjunction with antibiotic therapy.
Broad-spectrum antibiotics should be prescribed with caution in individuals with a history of gastrointestinal disease, particularly colitis.
Cephalosporins may be associated with a fall in prothrombin activity. Those at risk include patients with renal or hepatic impairment, or poor nutritional state, as well as patients receiving a protracted course of antimicrobial therapy, and patients previously stabilized on anticoagulant therapy. Prothrombin time should be monitored in patients at risk and exogenous vitamin K administered as indicated.
Patients should be counseled that antibacterial drugs including Cephalexin () capsules, Cephalexin () for oral suspension, and Cephalexin () tablets should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Cephalexin () capsules, Cephalexin () for oral suspension, or Cephalexin () tablets are 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 () capsules, Cephalexin () for oral suspension, Cephalexin () tablets, 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.
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 , ).
Cephalexin () Adverse Reactions
AlIergic 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 and , ). If seizures associated with drug therapy should occur, the drug should be discontinued. Anticonvulsant therapy can be given if clinically indicated.
Prolonged prothrombin time, increased BUN, increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated LDH, pancytopenia, leukopenia, and agranulocytosis.
To report SUSPECTED ADVERSE EVENTS, contact FDA at 1-800-FDA-1088 or www.fda.gov.
Cephalexin () Overdosage
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 (). 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.
Cephalexin () Dosage And Administration
Cephalexin () is administered orally.
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.
125 mg per 5 mL (200 mL when mixed):
250 mg per 5 mL (100 mL when mixed):
250 mg per 5 mL (200 mL when mixed):
*
Cephalexin () How Supplied
(a cherry mixed fruit flavored formula)—
125 mg/5 mL: bottles of 200 mL NDC 21695-789-20.
250 mg/5 mL: bottles of 100 mL NDC 21695-551-00 and 200 mL NDC 21695-551-20.
Directions for mixing are included on the label.
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
Shake well before using. Keep tightly closed.
Cephalexin () References
Sellersville, PA 18960
Rev. N 1/2010
Repackaged by:
Thousand Oaks, CA 91320
Cephalexin ()
