CEPHALEXIN: 7,901 Adverse Event Reports & Safety Profile

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, USP has the following structural formula: C 16 H 17 N 3 O 4 S•H 2 O M.W.

365.41 The nucleus of cephalexin, USP 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, USP in water is approximately 4.5 to 5. The crystalline form of cephalexin, USP 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, USP 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 monohydrate, USP equivalent to 250 mg (720 μmol) or 500 mg (1,439 μmol) of cephalexin.

Inactive

Ingredients: CAPSULES: magnesium stearate, silicon dioxide, and sodium starch glycolate.

Capsule

Shell and Print Constituents: black iron oxide, D&C Yellow #10 Aluminum Lake, FD&C Blue #1 Aluminum Lake, FD&C Blue #2 Aluminum Lake, FD&C Red #40 Aluminum Lake, gelatin, pharmaceutical glaze modified in SD-45, silicon dioxide or carboxymethylcellulose sodium, sodium lauryl sulfate, titanium dioxide and may contain propylene glycol. In addition, the 250 mg capsule shell contains yellow iron oxide. After mixing, each 5 mL of cephalexin for oral suspension USP will contain cephalexin monohydrate, USP equivalent to 125 mg (360 μmol) or 250 mg (720 μmol) of cephalexin.

Inactive

Ingredients: SUSPENSION: FD&C Red #40, cherry mixed fruit flavor (artificial flavors, benzyl alcohol, maltodextrin, and modified corn starch), silicon dioxide, sodium benzoate, sugar (fruit granulated), and xanthan gum. Each tablet contains cephalexin monohydrate, USP equivalent to 250 mg (720 μmol) or 500 mg (1,439 μmol) of cephalexin.

Inactive

Ingredients: TABLETS: hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, sodium starch glycolate, and titanium dioxide. structure

AND USAGE Cephalexin capsules are a cephalosporin antibacterial drug indicated for the treatment of the following infections caused by susceptible isolates of designated bacteria:

• Respiratory tract infection ( Error! Hyperlink reference not valid. )
• Otitis media ( Error! Hyperlink reference not valid. )
• Skin and skin structure infections ( Error! Hyperlink reference not valid. )
• Bone infections ( Error! Hyperlink reference not valid. )
• Genitourinary tract infections ( Error! Hyperlink reference not valid. ) 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 infections that are proven or strongly suspected to be caused by bacteria. ( Error! Hyperlink reference not valid. )

1.1 Respiratory Tract Infections Cephalexin capsules are indicated for the treatment of respiratory tract infections caused by susceptible isolates of Streptococcus pneumoniae and Streptococcus pyogenes.

1.2 Otitis Media Cephalexin capsules are indicated for the treatment of otitis media caused by susceptible isolates of Streptococcus pneumoniae , Haemophilus influenzae , Staphylococcus aureus , Streptococcus pyogenes , and Moraxella catarrhalis.

1.3 Skin and Skin Structure Infections Cephalexin capsules are indicated for the treatment of skin and skin structure infections caused by susceptible isolates of the following Gram-positive bacteria: Staphylococcus aureus and Streptococcus pyogenes .

1.4 Bone Infections Cephalexin capsules are indicated for the treatment of bone infections caused by susceptible isolates of Staphylococcus aureus and Proteus mirabilis.

1.5 Genitourinary Tract Infections Cephalexin capsules are indicated for the treatment of genitourinary tract infections, including acute prostatitis, caused by susceptible isolates of Escherichia coli , Proteus mirabilis , and Klebsiella pneumoniae .

1.6 Usage 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 infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information is available, this information 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.

AND ADMINISTRATION Adults and patients at least 15 years of age The usual dose is 250 mg every 6 hours, but a dose of 500 mg every 12 hours may be administered ( 2.1 ). Pediatric patients (over 1 year of age)

• Otitis media: 75 to 100 mg/kg in equally divided doses every 6 hours ( 2.2 )
• All other indications: 25 to 50 mg/kg given in equally divided doses ( 2.2 )
• In severe infections: 50 to 100 mg/kg may be administered in equally divided doses ( 2.2 )
• Duration of therapy ranges from 7 to 14 days depending on the infection type and severity. ( 2 )
• Dosage adjustment is required in patients with severe and end stage renal disease (ESRD) defined as creatinine clearance below 30 mL/min. ( 2.3 )

2.1 Adults and Pediatric Patients at Least 15 Years of Age The usual dose of oral cephalexin is 250 mg every 6 hours, but a dose of 500 mg every 12 hours may be administered. Treatment is administered for 7 to 14 days. For more severe infections larger doses of oral cephalexin may be needed, up to 4 grams daily in two to four equally divided doses.

2.2 Pediatric Patients (over 1 year of age) The recommended total daily dose of oral cephalexin for pediatric patients is 25 to 50 mg/kg given in equally divided doses for 7 to 14 days. In the treatment of β-hemolytic streptococcal infections, duration of at least 10 days is recommended. In severe infections, a total daily dose of 50 to 100 mg/kg may be administered in equally divided doses. For the treatment of otitis media, the recommended daily dose is 75 to 100 mg/kg given in equally divided doses. Cephalexin for oral suspension Weight 10 kg (22 lb) 125mg/5mL ½ to 1 tsp q.i.d. 250mg/5mL ¼ to ½ tsp q.i.d. 20 kg (44 lb) 40 kg (88 lb) 1 to 2 tsp q.i.d. 2 to 4 tsp q.i.d. Or ½ to 1 tsp q.i.d. 1 to 2 tsp q.i.d.

Weight

10 kg (22 lb) 20 kg (44 lb) 125mg/5mL 1 to 2 tsp b.i.d. 2 to 4 tsp b.i.d. 250mg/5mL ½ to 1 tsp b.i.d. 1 to 2 tsp b.i.d. 40 kg (88 lb) 4 to 8 tsp b.i.d. 2 to 4 tsp b.i.d. Directions for Mixing 125 mg per 5 mL (100 mL when mixed): Prepare suspension time at dispensing. Add to the bottle a total of 69 mL of water. For ease in preparation, tap bottle to loosen powder, add the water in 2 portions, shaking well after each addition. The resulting suspension will contain cephalexin monohydrate equivalent to 125 mg cephalexin in each 5 mL (teaspoonful). 125 mg per 5 mL (200 mL when mixed): Prepare suspension time at dispensing. Add to the bottle a total of 138 mL of water. For ease in preparation, tap bottle to loosen powder, add the water in 2 portions, shaking well after each addition. The resulting suspension will contain cephalexin monohydrate equivalent to 125 mg cephalexin in each 5 mL (teaspoonful). 250 mg per 5 mL (100 mL when mixed): Prepare suspension time at dispensing. Add to the bottle a total of 69 mL of water. For ease in preparation, tap bottle to loosen powder, add the water in 2 portions, shaking well after each addition. The resulting suspension will contain cephalexin monohydrate equivalent to 250 mg cephalexin in each 5 mL (teaspoonful). 250 mg per 5 mL (200 mL when mixed): Prepare suspension time at dispensing. Add to the bottle a total of 138 mL of water. For ease in preparation, tap bottle to loosen powder, add the water in 2 portions, shaking well after each addition. The resulting suspension will contain cephalexin monohydrate equivalent to 250 mg cephalexin in each 5 mL (teaspoonful). * After mixing, store in refrigerator. May be kept for 14 days without significant loss of potency.

2.3 Dosage Adjustments in Adult and Pediatric Patients at Least 15 Years of Age with Renal Impairment Administer the following dosing regimens for cephalexin for oral suspension to patients with impaired renal function [ see Warnings and Precautions (5.4) and Use in Specific Populations (8.6) ].

Table

1.

Recommended Dose

Regimen for Patients with Renal Impairment Renal function Dose regimen recommendation Creatinine clearance ≥ 60 mL/min No dose adjustment Creatinine clearance 30 to 59 mL/min No dose adjustment; maximum daily dose should not exceed 1 g Creatinine clearance 15 to 29 mL/min 250 mg, every 8 hours or every 12 hours Creatinine clearance 5 to 14 mL/min not yet on dialysis * 250 mg, every 24 hours Creatinine clearance 1 to 4 mL/min not yet on dialysis * 250 mg, every 48 hours or every 60 hours * There is insufficient information to make dose adjustment recommendations in patients on hemodialysis.

Cephalexin capsules are contraindicated in patients with known hypersensitivity to cephalexin or other members of the cephalosporin class of antibacterial drugs. Patients with known hypersensitivity to cephalexin or other members of the cephalosporin class of antibacterial drugs. ( Error! Hyperlink reference not valid. )

REACTIONS The following serious events are described in greater detail in the Warning and Precautions section:

• Hypersensitivity reactions [see Error! Hyperlink reference not valid. ]
• Clostridium difficile -associated diarrhea [see Error! Hyperlink reference not valid. ]
• Direct Coombs’ Test Seroconversion [see Error! Hyperlink reference not valid. ]
• Seizure Potential [see Error! Hyperlink reference not valid. ]
• Effect on Prothrombin Activity [see Error! Hyperlink reference not valid. ]
• Development of Drug-Resistant Bacteria [see Error! Hyperlink reference not valid. ] The most common adverse reactions associated with cephalexin include diarrhea, nausea, vomiting, dyspepsia and abdominal pain . ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Aurobindo Pharma USA, Inc. at 1-866-850-2876 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. In clinical trials, the most frequent adverse reaction was diarrhea. Nausea and vomiting, dyspepsia, gastritis, and abdominal pain have also occurred. As with penicillins and other cephalosporins, transient hepatitis and cholestatic jaundice have been reported. Other reactions have included hypersensitivity reactions, genital and anal pruritus, genital candidiasis, vaginitis and vaginal discharge, dizziness, fatigue, headache, agitation, confusion, hallucinations, arthralgia, arthritis, and joint disorder. Reversible interstitial nephritis has been reported. Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia, and slight elevations in aspartate transaminase (AST) and alanine transaminase (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 other altered laboratory tests have been reported for cephalosporin class antibacterial drugs: Other Adverse Reactions : Fever, colitis, aplastic anemia, hemorrhage, renal dysfunction, and toxic nephropathy.

Altered Laboratory

Tests : Prolonged prothrombin time, increased blood urea nitrogen (BUN), increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated lactate dehydrogenase (LDH), pancytopenia, leukopenia, and agranulocytosis.

AND PRECAUTIONS

• Serious hypersensitivity (anaphylactic) reactions : Prior to use, inquire regarding history of hypersensitivity to beta-lactam antibacterial drugs. Discontinue the drug if signs or symptoms of an allergic reaction occur and institute supportive measures. ( Error! Hyperlink reference not valid. )
• Clostridium difficile -associated diarrhea (CDAD ): Evaluate if diarrhea occurs. ( Error! Hyperlink reference not valid. )
• Direct Coombs’ Test Seroconversion : If anemia develops during or after cephalexin therapy, evaluate for drug-induced hemolytic anemia. ( Error! Hyperlink reference not valid. )
• Seizure Potential : Use lower dose in patients with renal impairment. ( Error! Hyperlink reference not valid. )

5.1 Hypersensitivity Reactions Allergic reactions in the form of rash, urticaria, angioedema, anaphylaxis, erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis have been reported with the use of cephalexin. Before therapy with cephalexin is instituted, inquire whether the patient has a history of hypersensitivity reactions to cephalexin, cephalosporins, penicillins, or other drugs. Cross-hypersensitivity among beta-lactam antibacterial drugs may occur in up to 10% of patients with a history of penicillin allergy. If an allergic reaction to cephalexin occurs, discontinue the drug and institute appropriate treatment.

5.2 Clostridium difficile -Associated Diarrhea 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.

5.3 Direct Coombs’ Test Seroconversion Positive direct Coombs’ tests have been reported during treatment with the cephalosporin antibacterial drugs including cephalexin. Acute intravascular hemolysis induced by cephalexin therapy has been reported. If anemia develops during or after cephalexin therapy, perform a diagnostic work-up for drug-induced hemolytic anemia, discontinue cephalexin and institute appropriate therapy.

5.4 Seizure Potential Several cephalosporins have been implicated in triggering seizures, particularly in patients with renal impairment when the dosage was not reduced. If seizures occur, discontinue cephalexin. Anticonvulsant therapy can be given if clinically indicated.

5.5 Prolonged Prothrombin Time Cephalosporins may be associated with prolonged prothrombin time. Those at risk include patients with renal or hepatic impairment, or poor nutritional state, as well as patients receiving a protracted course of antibacterial therapy, and patients receiving anticoagulant therapy. Monitor prothrombin time in patients at risk and manage as indicated.

5.6 Development of Drug-Resistant Bacteria Prescribing cephalexin in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria. 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.

PRECAUTIONS General 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. Information for Patients 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.

Drug Interactions

Metformin In healthy subjects given single 500 mg doses of cephalexin and metformin, plasma metformin mean C max 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, 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. 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/m 2 .

Pregnancy 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/m 2 , 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.

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 mcg/mL, then decreased gradually, and had disappeared 8 hours after administration. Caution should be exercised when cephalexin 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.

Geriatric

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 ).

INTERACTIONS

• Metformin: increased metformin concentrations. Monitor for hypoglycemia. ( Error! Hyperlink reference not valid. )
• Probenecid-The renal excretion of cephalexin is inhibited by probenecid. Co-administration of probenecid with cephalexin is not recommended. ( Error! Hyperlink reference not valid. )
• Administration of cephalexin may result in a false-positive reaction glucose in the urine. ( Error! Hyperlink reference not valid. )

7.1 Metformin Administration of cephalexin with metformin results in increased plasma metformin concentrations and decreased renal clearance of metformin. Careful patient monitoring and dose adjustment of metformin is recommended in patients concomitantly taking cephalexin and metformin <span class="opacity-50 text-xs">[see Error! Hyperlink reference not valid. ]</span>.

7.2 Probenecid The renal excretion of cephalexin is inhibited by probenecid. Co-administration of probenecid with cephalexin is not recommended.

7.3 Interaction with Laboratory or Diagnostic Testing A false-positive reaction may occur when testing for the presence of glucose in the urine using Benedict’s solution or Fehling’s solution.