Cephalexin

Cephalexin is a first-generation cephalosporin antibiotic prescribed to combat a wide range of bacterial infections. It functions by inhibiting bacterial cell wall synthesis, leading to the eradication of susceptible pathogens. This medication is a cornerstone in outpatient treatment due to its reliable efficacy and favorable safety profile when used appropriately under medical supervision.

Features

• Active Ingredient: Cephalexin (as monohydrate)
• Drug Class: First-generation cephalosporin antibiotic
• Administration: Oral (capsules, tablets, oral suspension)
• Bioavailability: Well-absorbed from the gastrointestinal tract
• Mechanism: Bactericidal; inhibits cell wall synthesis
• Spectrum: Effective against many Gram-positive and some Gram-negative bacteria

Benefits

• Rapid onset of action to quickly reduce infection symptoms
• High clinical cure rates for common bacterial infections
• Convenient oral administration suitable for outpatient treatment
• Generally well-tolerated with a established safety profile
• Effective alternative for patients with penicillin allergies (with appropriate caution)
• Comprehensive coverage against common community-acquired pathogens

Common use

Cephalexin is indicated for the treatment of infections caused by susceptible strains of microorganisms, including respiratory tract infections, otitis media, skin and skin structure infections, bone infections, and genitourinary tract infections. It is particularly effective against streptococci, staphylococci (including penicillinase-producing strains), Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae. Medical professionals prescribe cephalexin based on culture and susceptibility testing when possible, though empirical therapy is often initiated in community settings.

Dosage and direction

The dosage of cephalexin varies according to the infection being treated. For adults, the usual dose is 250 mg every 6 hours, or 500 mg every 12 hours. For more severe infections, doses may be increased to 500 mg every 6 hours or 1 g every 12 hours. The total daily dose should not exceed 4 grams. For pediatric patients, the recommended dosage is 25-50 mg/kg/day in divided doses, with severe infections potentially requiring 75-100 mg/kg/day in divided doses. Administration should continue for a minimum of 48-72 hours beyond the time the patient becomes asymptomatic or evidence of bacterial eradication has been obtained. The medication may be taken with or without food; however, taking with food may minimize potential gastrointestinal discomfort.

Precautions

Patients should complete the entire course of therapy even if symptoms improve to prevent the development of antibiotic-resistant bacteria. Use with caution in patients with renal impairment; dosage adjustments are necessary for patients with creatinine clearance less than 50 mL/min. Prolonged use may result in overgrowth of nonsusceptible organisms, including fungi. Clostridium difficile-associated diarrhea has been reported with nearly all antibacterial agents and may range in severity from mild diarrhea to fatal colitis. Patients should be monitored for signs of superinfection during and after treatment.

Contraindications

Cephalexin is contraindicated in patients with known hypersensitivity to cephalexin or any component of the formulation, or to other cephalosporins. Cross-hypersensitivity may occur in patients allergic to penicillin; approximately 10% of patients with penicillin allergy will also be allergic to cephalosporins. The antibiotic should not be administered to patients who have experienced anaphylactic reactions to penicillins.

Possible side effect

Common adverse reactions include gastrointestinal disturbances (diarrhea, nausea, vomiting, abdominal pain, dyspepsia) occurring in approximately 5-10% of patients. Other reported side effects include dizziness, fatigue, headache, genital pruritus, vaginitis, and vaginal discharge. Hypersensitivity reactions may manifest as rash, urticaria, angioedema, and rarely, anaphylaxis. Transient elevations in hepatic enzymes, eosinophilia, and neutropenia have been reported. As with other beta-lactam antibiotics, interstitial nephritis and reversible hepatitis have occurred in rare instances.

Drug interaction

Probenecid may decrease renal tubular secretion of cephalexin, resulting in increased and prolonged blood levels. Concomitant use with potent diuretics may increase the risk of nephrotoxicity. Cephalexin may produce false-positive reactions for glucose in the urine with Benedict’s solution, Fehling’s solution, or with Clinitest tablets. The antibiotic may cause a false-positive direct Coombs test. Concurrent use with oral anticoagulants may potentiate anticoagulant effects, though this interaction is less pronounced than with some other antibiotics.

Missed dose

If a dose is missed, it should be taken as soon as remembered. However, if it is almost time for the next dose, the missed dose should be skipped and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed dose, as this may increase the risk of adverse effects. Maintaining consistent antibiotic levels is important for therapeutic efficacy, so patients should strive to adhere to the prescribed dosing schedule.

Overdose

Symptoms of overdose may include nausea, vomiting, epigastric distress, diarrhea, and hematuria. In the event of overdose, general supportive measures are recommended. Gastric lavage may be indicated if performed soon after ingestion. Cephalexin is eliminated primarily by the kidneys, so forced diuresis, peritoneal dialysis, hemodialysis, or charcoal hemoperfusion may be considered in severe cases. Serum levels of cephalexin can be reduced by hemodialysis.

Storage

Cephalexin capsules and tablets should be stored at controlled room temperature (20-25°C or 68-77°F) in a tight, light-resistant container. The oral suspension, after reconstitution, should be stored in the refrigerator between 2-8°C (36-46°F) and discarded after 14 days. Keep all medications out of reach of children and pets. Do not use after the expiration date printed on the packaging.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Cephalexin is a prescription medication that should only be used under the supervision of a qualified healthcare professional. Patients should not self-diagnose or self-medicate with this antibiotic. Always consult with a healthcare provider for proper diagnosis and treatment recommendations. The complete prescribing information should be reviewed before initiating therapy.

Reviews

Clinical studies and extensive post-marketing surveillance demonstrate cephalexin’s effectiveness in treating susceptible bacterial infections. In clinical trials involving respiratory tract infections, success rates typically exceed 85-90% when pathogens are susceptible. Dermatologic studies show similar efficacy rates for skin and soft tissue infections. The antibiotic generally receives positive evaluations from medical professionals for its predictable pharmacokinetics, reliable absorption, and generally favorable tolerability profile. Patient satisfaction surveys indicate good symptom relief within 24-48 hours of initiation when used for appropriate indications.