Keflex: Potent Cephalosporin Antibiotic for Bacterial Infections
Keflex
| Product dosage: 250mg | |||
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| 360 | $0.88
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| Product dosage: 500mg | |||
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Keflex (cephalexin) is a first-generation cephalosporin antibiotic prescribed for the treatment of a wide spectrum of bacterial infections. It operates by inhibiting bacterial cell wall synthesis, leading to the eradication of susceptible organisms. This medication is a cornerstone in outpatient management due to its reliable efficacy, favorable safety profile, and broad coverage against common pathogens. Proper diagnosis and adherence to prescribed regimens are critical for optimal therapeutic outcomes and mitigating antibiotic resistance.
Features
- Active pharmaceutical ingredient: Cephalexin
- Available in oral formulations: 250 mg, 500 mg, and 750 mg capsules; 125 mg/5 mL and 250 mg/5 mL oral suspensions
- Belongs to the beta-lactam antibiotic class, specifically first-generation cephalosporins
- Demonstrates bactericidal activity by binding to penicillin-binding proteins (PBPs)
- Exhibits stability against staphylococcal penicillinases
- Typically administered two to four times daily, depending on infection severity
Benefits
- Effectively treats common bacterial infections including skin/soft tissue, respiratory, and urinary tract infections
- Rapid onset of action, with symptomatic improvement often observed within 48–72 hours of initiation
- Well-established safety and tolerability profile in both adult and pediatric populations (over 1 year old)
- Oral bioavailability allows for convenient outpatient therapy, reducing need for hospitalization
- Lower risk of Clostridioides difficile infection compared to broader-spectrum alternatives
- Cost-effective generic availability improves accessibility for long-term treatment courses when necessary
Common use
Keflex is indicated for the treatment of infections caused by susceptible strains of designated microorganisms. Common clinical applications include skin and skin structure infections such as cellulitis, abscesses, and wound infections, often attributable to Staphylococcus aureus and Streptococcus pyogenes. It is also employed for respiratory tract infections, including pharyngitis, tonsillitis, and community-acquired pneumonia of mild to moderate severity. In genitourinary practice, it is used for uncomplicated urinary tract infections caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae. Off-label uses may include dental prophylaxis in specific high-risk patients and orthopedic prophylaxis, though guidelines should be consulted.
Dosage and direction
Dosage must be individualized based on the infection site, severity, and causative organism, as well as renal function. For adults, the usual dose ranges from 250 mg to 1 gram every 6 hours. For mild to moderate upper respiratory infections, 500 mg every 12 hours may be sufficient. Pediatric dosing is typically 25–50 mg/kg/day divided into 2–4 doses, not exceeding adult doses. In patients with renal impairment (creatinine clearance <50 mL/min), dosage reduction is necessary. Administration with food may minimize gastrointestinal upset. The full prescribed course should be completed even if symptoms resolve earlier to prevent recurrence and resistance development.
Precautions
Use with caution in patients with a history of gastrointestinal disease, particularly colitis. Renal function should be assessed before and during prolonged therapy. As with all antibiotics, Keflex may result in overgrowth of nonsusceptible organisms, including fungi; monitor for superinfection. Use in pregnancy (Category B) should be reserved for cases where clearly needed; it is excreted in breast milk. In patients with a history of mild penicillin allergy, caution is advised due to potential cross-reactivity (estimated 5–10%), though cephalosporins are often tolerated. Avoid unnecessary use to reduce the development of drug-resistant bacteria.
Contraindications
Keflex is contraindicated in patients with known hypersensitivity to cephalexin or any component of the formulation. It is also contraindicated in patients with a history of severe, immediate hypersensitivity reactions (e.g., anaphylaxis) to any other beta-lactam antibiotic (e.g., penicillins, other cephalosporins). Should not be used for the treatment of viral infections, such as the common cold or influenza.
Possible side effect
Common adverse reactions (≥1%) include gastrointestinal disturbances: diarrhea, nausea, vomiting, dyspepsia, and abdominal pain. Dermatological reactions such as rash and urticaria may occur. Less frequently, patients may experience dizziness, fatigue, headache, or genital pruritus. Transient elevations in hepatic enzymes or eosinophilia have been reported. Serious but rare side effects include pseudomembranous colitis (indicated by severe diarrhea), Stevens-Johnson syndrome, allergic reactions ranging from rash to anaphylaxis, and reversible interstitial nephritis. Patients should seek immediate medical attention for signs of severe allergic reaction or bloody diarrhea.
Drug interaction
Probenecid may reduce renal tubular secretion of cephalexin, increasing and prolonging its blood levels. Concomitant use with potent diuretics (e.g., furosemide) may increase the risk of nephrotoxicity. Keflex may potentiate the effect of oral anticoagulants (e.g., warfarin) by altering vitamin K metabolism or gut flora, requiring closer INR monitoring. Bacteriostatic antibiotics (e.g., tetracyclines, erythromycin) may interfere with its bactericidal action. Avoid concurrent use with live bacterial vaccines. Always review the patient’s full medication list for potential interactions.
Missed dose
If a dose is missed, it should be taken as soon as it is remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped, and the regular dosing schedule resumed. Doubling the dose to make up for a missed one is not recommended, as it may increase the risk of adverse effects without improving efficacy. Patients should be counseled on the importance of adherence to prevent decreased effectiveness and development of resistance.
Overdose
Symptoms of overdose primarily involve exacerbation of adverse effects, notably nausea, vomiting, epigastric distress, diarrhea, and hematuria. In cases of significant overdose, neurotoxicity (e.g., hallucinations, seizures) may occur, especially in patients with renal impairment. Management is supportive and symptomatic; gastric lavage may be considered if ingestion was recent. Hemodialysis can remove cephalexin from the bloodstream and may be employed in severe cases, particularly with renal compromise. There is no specific antidote.
Storage
Store at room temperature (20–25°C or 68–77°F), in a tightly closed container, and protect from light and moisture. Keep out of reach of children. The oral suspension, once reconstituted, should be stored in a refrigerator and discarded after 14 days. Do not freeze. Dispose of unused medication via a drug take-back program or according to local regulations to avoid environmental contamination or accidental ingestion.
Disclaimer
This information is for educational purposes only and does not constitute medical advice. Keflex is a prescription medication and should only be used under the supervision of a qualified healthcare professional. The patient must consult their physician for diagnosis, appropriate treatment, and personalized dosing instructions. Never initiate, adjust, or discontinue therapy without professional guidance.
Reviews
“Prescribed Keflex for a stubborn skin infection after a minor surgery. Noticed a significant reduction in redness and swelling within two days. Completed the 10-day course with no side effects aside from mild initial nausea. Highly effective.” – Maria K., verified patient
“As an infectious disease specialist, I find cephalexin remains a workhorse for outpatient management of MSSA and streptococcal infections. Its predictable pharmacokinetics and generally good tolerability make it a first-line choice for many uncomplicated cases. Resistance patterns should always guide therapy.” – Dr. Evan R., MD
“Used for my child’s ear infection. The suspension was easy to administer, and symptoms improved quickly. We did experience some diarrhea towards the end of the course, but it resolved after finishing the medication. Would use again if recommended.” – James L., parent