Cephalexin

Pronunciation

(sef a LEKS in)

U.S. Brand Names

Biocef®; Keflex®; Panixine DisperDose™

Synonyms

Cephalexin Monohydrate

Generic Available

Yes: Excludes tablet for oral suspension

Canadian Brand Names

Apo-Cephalex®; Keftab®; Novo-Lexin®; Nu-Cephalex

Use

Treatment of susceptible bacterial infections including respiratory tract infections, otitis media, skin and skin structure infections, bone infections and genitourinary tract infections, including acute prostatitis; alternative therapy for acute bacterial endocarditis prophylaxis

Use - Dental

Prophylaxis in total joint replacement patients undergoing dental procedures which produce bacteremia; alternative antibiotic for prevention of bacterial endocarditis

Note: Individuals allergic to amoxicillin (penicillins) may receive cephalexin provided they have not had an immediate, local, or systemic IgE-mediated anaphylactic allergic reaction to penicillin.

Pregnancy Risk Factor

Lactation

Enters breast milk (small amounts)/use caution

Contraindications

Hypersensitivity to cephalexin, any component of the formulation, or other cephalosporins

Warnings/Precautions

Modify dosage in patients with severe renal impairment, prolonged use may result in superinfection; use with caution in patients with a history of penicillin allergy, especially IgE-mediated reactions (eg, anaphylaxis, urticaria). May cause antibiotic-associated colitis or colitis secondary to C. difficile .

Adverse Reactions

Frequency not defined.

Central nervous system: Agitation, confusion, dizziness, fatigue, hallucinations, headache

Dermatologic: Angioedema, erythema multiforme (rare), rash, Stevens-Johnson syndrome (rare), toxic epidermal necrolysis (rare), urticaria

Gastrointestinal: Abdominal pain, diarrhea, dyspepsia, gastritis, nausea (rare), pseudomembranous colitis, vomiting (rare)

Genitourinary: Genital pruritus, genital moniliasis, vaginitis, vaginal discharge

Hematologic: Eosinophilia, neutropenia, thrombocytopenia

Hepatic: AST/ALT increased, cholestatic jaundice (rare), transient hepatitis (rare)

Neuromuscular & skeletal: Arthralgia, arthritis, joint disorder

Renal: Interstitial nephritis (rare)

Miscellaneous: Allergic reactions

Overdosage/Toxicology

Symptoms of overdose include epigastric distress, diarrhea, hematuria, nausea, and vomiting. Many beta-lactam containing antibiotics have the potential to cause neuromuscular hyperirritability or seizures. Hemodialysis may be helpful to aid in removal of the drug from blood; otherwise, treatment is supportive and symptom-directed.

Drug Interactions

Aminoglycosides: Increase nephrotoxic potential.

Probenecid: High-dose probenecid decreases clearance of cephalexin.

Ethanol/Nutrition/Herb Interactions

Food: Peak antibiotic serum concentration is lowered and delayed, but total drug absorbed is not affected. Cephalexin serum levels may be decreased if taken with food.

Stability

Refrigerate suspension after reconstitution; discard after 14 days.

Tablet for oral suspension (Panixine DisperDose™): Tablets must be dissolved in ~10 mL water prior to administration, and should be used immediately after dissolving.

Mechanism of Action

Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins (PBPs) which in turn inhibits the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls, thus inhibiting cell wall biosynthesis. Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested.

Pharmacodynamics/Kinetics

Absorption: Delayed in young children

Distribution: Widely into most body tissues and fluids, including gallbladder, liver, kidneys, bone, sputum, bile, and pleural and synovial fluids; CSF penetration is poor; crosses placenta; enters breast milk

Protein binding: 6% to 15%

Half-life elimination: Adults: 0.5-1.2 hours; prolonged with renal impairment

Time to peak, serum: ~1 hour

Excretion: Urine (80% to 100% as unchanged drug) within 8 hours

Dosage

Oral:

Children >1 year: Dosing range: 25-50 mg/kg/day every 6-8 hours; more severe infections: 50-100 mg/kg/day in divided doses every 6-8 hours; maximum: 4 g/24 hours

Otitis media: 75-100 mg/kg/day in 4 divided doses

Streptococcal pharyngitis, skin and skin structure infections: 25-50 mg/kg/day divided every 12 hours

Uncomplicated cystitis: Children >15 years: Refer to Adults dosing

Prophylaxis of bacterial endocarditis (dental, oral, respiratory tract, or esophageal procedures): 50 mg/kg 1 hour prior to procedure (maximum: 2 g)

Adults: Dosing range: 250-1000 mg every 6 hours; maximum: 4 g/day

Streptococcal pharyngitis, skin and skin structure infections: 500 mg every 12 hours

Uncomplicated cystitis: 500 mg every 12 hours for 7-14 days

Prophylaxis of bacterial endocarditis (dental, oral, respiratory tract, or esophageal procedures): 2 g 1 hour prior to procedure

Dosing adjustment in renal impairment: Adults: Clcr<10 mL/minute: 250-500 mg every 12 hours

Hemodialysis: Moderately dialyzable (20% to 50%)

Administration

Take without regard to food. If GI distress, take with food. Give around-the-clock to promote less variation in peak and trough serum levels.

Panixine DisperDose™: Tablets should be mixed in ~10 mL of water immediately prior to administration. Drink entire solution, then rinse glass with additional water and drink contents to ensure entire dose has been taken. Tablets should not be chewed or swallowed whole.

Monitoring Parameters

With prolonged therapy monitor renal, hepatic, and hematologic function periodically; monitor for signs of anaphylaxis during first dose

Test Interactions

Positive direct Coombs', false-positive urinary glucose test using cupric sulfate (Benedict's solution, Clinitest®, Fehling's solution), false-positive serum or urine creatinine with Jaffé reaction, false-positive urinary proteins and steroids

Dietary Considerations

Take without regard to food. If GI distress, take with food. Panixine DisperDose™ contains phenylalanine 2.8 mg/cephalexin 125 mg.

Patient Education

Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. Do not take any new medication during therapy unless approved by prescriber. Take as directed, at regular intervals around-the-clock (with or without food). Chilling oral suspension improves flavor (do not freeze). Maintain adequate hydration (2-3 L/day of fluids) unless instructed to restrict fluid intake. Complete full course of medication, even if you feel better. May cause false test results with Clinitest®; use of another type of glucose testing is preferable. May cause diarrhea (buttermilk, boiled milk, or yogurt may help). Report unresolved diarrhea; unusual bruising or bleeding; changes in urinary pattern; or opportunistic infection (vaginal itching or drainage, sores in mouth, blood in urine or stool). Breast-feeding precaution: Consult prescriber if breast-feeding.

Cardiovascular Considerations

May be used for prevention of bacterial endocarditis.

Dental Health: Effects on Dental Treatment

No significant effects or complications reported

Dental Health: Vasoconstrictor/Local Anesthetic Precautions

No information available to require special precautions

Mental Health: Effects on Mental Status

May cause nervousness; case reports of euphoria, delusion, illusions, and depersonalization with cephalosporins

Mental Health: Effects on Psychiatric Treatment

May rarely cause neutropenia; use caution with clozapine and carbamazepine

Dosage Forms

Capsule: 250 mg, 500 mg

Biocef®: 500 mg

Keflex®: 250 mg, 500 mg

Powder for oral suspension: 125 mg/5 mL (100 mL, 200 mL); 250 mg/5 mL (100 mL, 200 mL)

Biocef®: 125 mg/5 mL (100 mL); 250 mg/5 mL (100 mL)

Tablet, for oral suspension (Panixine DisperDose™): 125 mg [contains phenylalanine 2.8 mg; peppermint flavor], 250 mg [contains phenylalanine 5.6 mg; peppermint flavor]

References

"Advisory Statement. Antibiotic Prophylaxis for Dental Patients With Total Joint Replacements. American Dental Association; American Academy of Orthopedic Surgeons," J Am Dent Assoc , 1997, 128(7):1004-8.

Dajani AS, Taubert KA, Wilson W, et al, "Prevention of Bacterial Endocarditis Recommendations by the American Heart Association," JAMA 1997, 277(22):1794-801.

Donowitz GR and Mandell GL, "Beta-Lactam Antibiotics," N Engl J Med , 1988, 318(7):419-26 and 318(8):490-500.

Saxon A, Beall GN, Rohr AS, et al, "Immediate Hypersensitivity Reactions to Beta-Lactam Antibiotics," Ann Intern Med , 1987, 107(2):204-15.

Smith GH, "Oral Cephalosporins in Perspective," DICP , 1990, 24(1):45-51.

International Brand Names

Apo-Cephalex® (CA); Keftab® (CA); Novo-Lexin® (CA); Nu-Cephalex (CA)

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