Keftab is a brand name for cephalexin, a first-generation cephalosporin antibiotic widely used in clinical practice since its introduction in the 1960s. Cephalexin belongs to the beta-lactam class of antibiotics, which also includes penicillins, and exerts its bactericidal effect by inhibiting bacterial cell wall synthesis. This report provides a detailed examination of Keftab, covering its pharmacology, indications, dosing, adverse effects, contraindications, drug interactions, resistance patterns, and clinical considerations, aiming to offer a thorough yet concise reference for healthcare professionals and students.
Pharmacology and Mechanism of Action
Cephalexin works by binding to penicillin-binding proteins (PBPs) located inside the bacterial cell wall. This binding inhibits the transpeptidase enzymes responsible for cross-linking peptidoglycan chains, a critical step in cell wall assembly. As a result, the bacterial cell wall becomes weakened, leading to osmotic lysis and death of susceptible bacteria. Cephalexin is primarily active against Gram-positive organisms, including Staphylococcus aureus (methicillin-susceptible), Streptococcus pyogenes, Streptococcus pneumoniae, and some Gram-negative bacteria like Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. It is not effective against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, or most anaerobic bacteria. The drug is well absorbed orally, with a bioavailability of approximately 90–95% after oral administration. Peak serum concentrations occur within one hour in fasting individuals. Cephalexin is widely distributed in body tissues and fluids, including bone, synovial fluid, and bile, but penetration into the central nervous system is poor unless the meninges are inflamed. It is primarily excreted unchanged by the kidneys via glomerular filtration and tubular secretion, with a half-life of about 0.5 to 1.2 hours in patients with normal renal function. Dose adjustment is necessary in patients with significant renal impairment (creatinine clearance <30 mL/min).
Clinical Indications
Keftab is FDA-approved for the treatment of respiratory tract infections (e.g., pharyngitis, tonsillitis, acute bronchitis, and community-acquired pneumonia caused by susceptible strains of S. pyogenes, S. pneumoniae, and S. aureus), skin and soft tissue infections (e.g., cellulitis, impetigo, and wound infections), bone infections (osteomyelitis), urinary tract infections (uncomplicated cystitis and pyelonephritis caused by E. coli, K. pneumoniae, or P. mirabilis), and otitis media. It is also used for prophylaxis of surgical site infections in certain procedures, particularly in patients with penicillin allergy who require coverage against Gram-positive organisms. However, it is important to note that cephalexin is not recommended for severe or complicated infections due to its limited spectrum and susceptibility to beta-lactamase degradation. In pediatric populations, it is commonly prescribed for ear infections and streptococcal pharyngitis.
Dosage and Administration
Keftab is available in oral formulations: capsules (250 mg, 500 mg, and 750 mg), tablets (250 mg and 500 mg), and oral suspension (125 mg/5 mL and 250 mg/5 mL). The typical adult dose for most infections is 250 mg to 500 mg every 6 to 8 hours (maximum 4 g per day). For severe infections such as osteomyelitis, doses up to 1 g every 6 hours may be used. Pediatric dosing is weight-based: 25–50 mg/kg/day divided into 3–4 doses for mild to moderate infections, or 75–100 mg/kg/day for severe infections. In patients with renal impairment, the dosing interval should be extended based on creatinine clearance: for CrCl 10–30 mL/min, give 250–500 mg every 12 hours; for CrCl <10 mL/min, give 250–500 mg every 24–36 hours. The drug should be taken with food if gastrointestinal upset occurs, but food does not significantly affect absorption.
Adverse Effects
Cephalexin is generally well tolerated. The most common adverse effects involve the gastrointestinal tract: diarrhea, nausea, vomiting, dyspepsia, and abdominal pain. Diarrhea may be due to direct irritation or Clostridioides difficile infection (CDI) in rare cases. Allergic reactions occur in about 1–10% of patients, ranging from mild rash and urticaria to severe anaphylaxis. Cross-reactivity with penicillins exists in approximately 5–10% of patients with a history of immediate-type penicillin allergy. Other rare but serious adverse effects include serum sickness-like reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis, drug-induced liver injury (elevated transaminases, cholestatic jaundice), acute interstitial nephritis, neutropenia, thrombocytopenia, and hemolytic anemia. Prolonged use may lead to superinfection with resistant organisms such as Candida albicans or C. difficile. Pseudomembranous colitis has been reported and requires discontinuation and appropriate management.
Contraindications and Precautions
Keftab is contraindicated in patients with a known hypersensitivity to cephalosporins or any component of the formulation. Caution is advised in patients with a history of penicillin allergy (especially IgE-mediated reactions) due to potential cross-reactivity. It should be used with caution in patients with renal impairment (dose adjustment needed), gastrointestinal disease (particularly colitis), and in those with a history of seizures (beta-lactams can lower seizure threshold at high doses). For pregnant women, cephalexin is categorized as FDA Pregnancy Category B: animal studies have not demonstrated fetal risk, but adequate human studies are lacking; it is generally considered safe for use during pregnancy when clearly indicated. It is excreted in breast milk in low concentrations and is considered compatible with breastfeeding.
Drug Interactions
Cephalexin can increase the effect of warfarin by prolonging prothrombin time, so INR monitoring is recommended. Concurrent use with probenecid decreases renal tubular secretion of cephalexin, leading to increased serum levels and prolonged half-life. Conversely, the absorption of cephalexin may be reduced by the co-administration of certain antacids (e.g., aluminum- or magnesium-containing) and iron supplements, so it is advisable to separate doses by at least 2 hours. Metformin levels may be slightly increased due to competition for tubular secretion, but this is rarely clinically significant. Live attenuated bacterial vaccines (e.g., oral typhoid) may be less effective during cephalexin therapy.
Resistance Patterns
Resistance to first-generation cephalosporins like cephalexin has increased over decades, particularly among healthcare-associated pathogens. The primary mechanisms include the production of beta-lactamases (e.g., TEM-1, SHV-1) that hydrolyze the beta-lactam ring, alterations in PBPs (as seen in MRSA), and decreased drug permeability in Gram-negative bacteria. Community-acquired MRSA is invariably resistant. Gram-negative resistance is also rising due to extended-spectrum beta-lactamases (ESBLs). Therefore, local antibiograms should guide empiric use. Cephalexin remains effective for many uncomplicated community-acquired infections caused by sensitive strains.
Clinical Considerations and Alternatives
Although newer generation cephalosporins offer broader coverage, Keftab remains a valuable agent due to its excellent oral bioavailability, low cost, and favorable safety profile. It is often a first-line choice for treating streptococcal pharyngitis, impetigo, and mild to moderate urinary tract infections in patients unable to tolerate penicillins. However, beta-lactamase inhibitors (e.g., amoxicillin-clavulanate) or second-generation cephalosporins (e.g., cefuroxime) may be preferred when broader Gram-negative coverage is needed. For patients with immediate-type penicillin allergy, alternative classes such as macrolides (azithromycin), clindamycin, or Flagyl ER 200mg; farmacianovapatraix.es, trimethoprim-sulfamethoxazole may be considered, though cross-reactivity with cephalosporins is low but not absent.
In conclusion, Keftab (cephalexin) is a time-tested, effective antibiotic for a variety of common bacterial infections, particularly those involving the skin, respiratory tract, and urinary system. Its role in therapy continues to be important in an era of rising resistance, provided that appropriate prescribing practices are followed, including culture-directed therapy when feasible. Healthcare providers should remain vigilant for adverse effects, drug interactions, and emerging resistance patterns to optimize patient outcomes.