Generic Keflex (Cephalexin)

Introduction

Keflex is an oral antibiotic whose active ingredient is the β-lactam cephalosporin cephalexin. It is supplied in tablet form in strengths of 250 mg and 500 mg. Cephalexin belongs to the first-generation cephalosporin class and is used to treat a variety of bacterial infections that are sensitive to this agent. The medication is indicated for infections of the skin, bone, ear, throat, urinary tract, and certain respiratory conditions. In addition, clinicians sometimes prescribe it off-label for infections not listed in the official labeling when susceptibility testing supports its use.

What is Keflex?

Keflex contains the chemical compound cephalexin, a semisynthetic derivative of the natural cephalosporin C. First described in the s, cephalexin was developed to provide a broader spectrum of activity than earlier penicillins while retaining oral bioavailability. The product is manufactured by several pharmaceutical companies; in the United States it is commonly marketed by the IMS Health division of Pfizer.

Keflex is the generic version of well-known medications, containing the active compound Cephalexin. Our online pharmacy provides this generic alternative as a cost-effective treatment option. It is also marketed under brand names such as Keflex, Ceporex, and Keflin in various regions.

How Keflex Works

Cephalexin exerts its antibacterial effect by binding to penicillin-binding proteins (PBPs) on the bacterial cell wall. This binding inhibits the transpeptidation step that cross-links peptidoglycan strands, weakening the wall and leading to osmotic lysis of susceptible organisms. Because the drug is bactericidal, bacterial counts fall rapidly after the first dose. Oral cephalexin reaches peak plasma concentrations within 30-60 minutes, and its half-life of .5-1 hour allows for convenient twice-daily dosing for most infections. The drug is primarily eliminated unchanged by the kidneys; renal function therefore influences dosing frequency and total daily dose.

Conditions Treated with Keflex

Skin and Soft-Tissue Infections - Cephalexin is active against Staphylococcus aureus (excluding methicillin-resistant strains) and Streptococcus pyogenes, making it suitable for cellulitis, impetigo, and infected wounds.

Bone and Joint Infections - When the organism is known to be cephalexin-susceptible, the drug can be used for uncomplicated osteomyelitis or septic arthritis, often after surgical debridement.

Ear Infections (Otitis Media) - The drug penetrates middle-ear fluid and treats common otitis media pathogens such as Streptococcus pneumoniae and non-MRSA Staphylococcus aureus.

Upper Respiratory Tract Infections - Indicated for streptococcal pharyngitis and tonsillitis, where rapid bacterial eradication shortens symptom duration.

Urinary Tract Infections - Effective against susceptible Escherichia coli, Klebsiella spp., and Proteus spp. when resistance patterns permit.

The efficacy in each condition is supported by susceptibility data from the Clinical and Laboratory Standards Institute (CLSI) and by randomized controlled trials comparing cephalexin to other first-line agents.

Off-Label and Investigational Uses of Keflex

• Prophylaxis for Dental Procedures in Patients with Certain Orthopedic Implants - Some clinicians use a single pre-procedure dose of cephalexin to reduce the risk of hematogenous spread to prosthetic joints, although formal guidelines have not endorsed this practice.

• Mild Community-Acquired Pneumonia in Low-Risk Adults - Small observational studies have reported clinical success with cephalexin for atypical presentations when the causative organism is a susceptible streptococcus.

• Complicated Skin Infections with Mixed Flora - In selected cases, cephalexin is added to broader-spectrum regimens to target residual gram-positive organisms.

All off-label applications lack FDA or EMA approval. Use should occur only under the direct supervision of a qualified healthcare professional, with susceptibility testing guiding therapy.

Is Keflex the Right Medication for You?

Keflex is most appropriate for adult patients with confirmed or strongly suspected infections caused by bacteria known to be susceptible to first-generation cephalosporins. Ideal candidates include:

• Individuals with uncomplicated cellulitis, pharyngitis, or uncomplicated urinary tract infection.
• Patients with normal renal function who can tolerate oral medications.
• Those requiring a cost-effective alternative to brand-name antibiotics.

Contraindications include a documented allergy to cephalosporins or penicillins (due to potential cross-reactivity), severe renal impairment without dose adjustment, and infections caused by methicillin-resistant Staphylococcus aureus (MRSA) or other resistant organisms. Pregnant or breastfeeding women should use cephalexin only when the benefit outweighs potential risk, as the drug crosses the placenta and is excreted in breast milk.

Risks, Side Effects, and Interactions

Common

• Nausea, vomiting, or abdominal discomfort
• Diarrhea (often mild, occasionally due to Clostridioides difficile)
• Rash or mild pruritus

Rare

• Elevated liver enzymes (transaminases)
• Eosinophilic pneumonia (very uncommon)
• Leukopenia or neutropenia

Serious

• Anaphylaxis or severe hypersensitivity reactions (including Stevens-Johnson syndrome)
• Acute interstitial nephritis
• Pseudomembranous colitis caused by C. difficile

Drug-Drug Interactions

• Probenecid - Decreases renal clearance of cephalexin, potentially increasing serum levels; dose adjustment may be required.
• Warfarin - Cephalexin may potentiate anticoagulant effects; monitor INR closely.