Phexin: Advanced Cephalosporin Therapy for Robust Bacterial Eradication
Phexin
Phexin (Cefalexin) is a first-generation cephalosporin antibiotic engineered to deliver potent, broad-spectrum bactericidal action against susceptible Gram-positive and Gram-negative pathogens. Its advanced formulation ensures high oral bioavailability and rapid tissue penetration, making it a cornerstone in outpatient and inpatient therapeutic regimens for a wide array of community-acquired infections. Trusted by clinicians globally, Phexin offers a reliable, well-tolerated option for effective infection resolution, minimizing the risk of treatment failure and supporting optimal patient recovery trajectories.
Features
- Active Pharmaceutical Ingredient: Cefalexin (as Cefalexin Monohydrate)
- Pharmacological Class: First-generation cephalosporin antibiotic
- Mechanism of Action: Inhibition of bacterial cell wall synthesis via binding to penicillin-binding proteins (PBPs)
- Spectrum of Activity: Effective against susceptible strains of Staphylococcus aureus (including penicillinase-producing strains), Streptococcus pneumoniae, Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae
- Formulations Available: 250 mg and 500 mg capsules; 125 mg/5 mL and 250 mg/5 mL oral suspensions
- Bioavailability: Approximately 90% following oral administration
- Peak Plasma Concentration: Achieved within 1 hour post-dose
- Protein Binding: Low (10-15%)
- Elimination Half-Life: ~0.5–1.2 hours in adults with normal renal function
- Excretion: Primarily renal (>90% unchanged in urine within 8 hours)
Benefits
- Rapid and potent bactericidal activity leading to swift reduction in bacterial load and symptomatic relief.
- High oral bioavailability ensures predictable pharmacokinetics and consistent therapeutic serum levels without the need for parenteral administration in most cases.
- Broad-spectrum coverage targets common community-acquired pathogens, reducing the need for empirical broad-spectrum agents and supporting antimicrobial stewardship.
- Well-established safety profile with a low incidence of severe adverse events, promoting patient adherence and completion of therapy.
- Flexible dosing regimens and multiple formulations (capsules, suspension) accommodate pediatric, adult, and geriatric populations, enhancing clinical utility.
- Cost-effective therapeutic option with proven efficacy, reducing overall healthcare burden and hospitalization rates for amenable infections.
Common use
Phexin is clinically indicated for the treatment of bacterial infections caused by susceptible organisms. Its primary applications include uncomplicated skin and skin structure infections such as cellulitis, impetigo, and abscesses often caused by Staphylococcus aureus and Streptococcus pyogenes. It is also highly effective in managing respiratory tract infections, including pharyngitis, tonsillitis, and acute bacterial exacerbations of chronic bronchitis, predominantly when attributable to Group A beta-hemolytic streptococci. Additionally, Phexin is utilized for urinary tract infections like cystitis and pyelonephritis caused by susceptible E. coli, Proteus mirabilis, and Klebsiella species. Off-label uses, under specialist supervision, may include surgical prophylaxis in specific clean-contaminated procedures and adjunctive therapy in odontogenic infections.
Dosage and direction
Dosage must be individualized based on the infection’s severity, causative organism susceptibility, and the patient’s renal function.
Adults: The typical adult dosage for most mild to moderate infections is 250 mg to 500 mg orally every 6 hours. For more severe infections or those caused by less susceptible organisms, doses of 1 gram every 6 to 12 hours may be required. The maximum daily dose should not exceed 4 grams.
Pediatric Patients: The recommended dosage is 25 to 50 mg/kg/day divided into four equal doses. For severe infections, the dosage may be increased to 100 mg/kg/day, not to exceed adult maximum doses. For otitis media caused by Streptococcus pneumoniae, a dosage of 75 to 100 mg/kg/day divided into four doses is recommended.
Administration: Phexin capsules or oral suspension can be taken with or without food; however, administration with food may minimize potential gastrointestinal upset. The oral suspension should be shaken well before each use. Patients should be instructed to complete the entire prescribed course of therapy, even if symptoms subside before the medication is finished, to prevent the development of resistant bacteria.
Renal Impairment: Dosage adjustment is necessary in patients with impaired renal function (creatinine clearance <50 mL/min). A recommended guideline is to administer 500 mg loading dose, followed by 250 to 500 mg every 8-12 hours for mild impairment (CLcr 30-50 mL/min), every 12 hours for moderate impairment (CLcr 10-29 mL/min), and every 24 hours for severe impairment (CLcr <10 mL/min).
Precautions
- General: Prescribe with caution in patients with a history of gastrointestinal disease, particularly colitis, as antibiotic use can cause pseudomembranous colitis.
- Renal Function: Use with caution in patients with renal impairment; dosage reduction is imperative to prevent accumulation and potential toxicity.
- Hepatic Function: Although primarily renally excreted, monitor patients with severe hepatic impairment concomitantly with renal dysfunction.
- Prolonged Use: Extended antibiotic therapy may result in overgrowth of non-susceptible organisms, including fungi. Constant observation of the patient is essential; if superinfection occurs during therapy, appropriate measures should be taken.
- Laboratory Tests: Perform culture and susceptibility studies prior to and during therapy to isolate and identify causative organisms and determine their susceptibility to cefalexin. In patients with renal impairment, periodic renal function assessments are advised.
- Phenylketonurics: The oral suspension contains aspartame, which metabolizes to phenylalanine; use with caution in patients with phenylketonuria.
Contraindications
Phexin is contraindicated in patients with known hypersensitivity to cefalexin, any component of the formulation, or other cephalosporin-class antibiotics. A history of severe hypersensitivity (e.g., anaphylactic reaction) to any beta-lactam antibiotic (penicillins, cephalosporins, carbapenems) is a relative contraindication due to the potential for cross-reactivity.
Possible side effect
The following adverse reactions have been reported with cefalexin use. Most are generally mild and transient.
Gastrointestinal: Diarrhea (common), nausea, vomiting, abdominal pain, dyspepsia, and, rarely, pseudomembranous colitis (which may manifest as severe, persistent diarrhea). Hypersensitivity Reactions: Skin rash, urticaria, pruritus, and, rarely, erythema multiforme, Stevens-Johnson syndrome, or anaphylaxis. Central Nervous System: Dizziness, fatigue, headache, confusion (especially in renal impairment). Hepatic: Transient elevations in liver enzymes (AST, ALT, alkaline phosphatase). Renal: Reversible interstitial nephritis, elevated BUN and serum creatinine. Hematologic: Transient neutropenia, leukopenia, thrombocytopenia, positive Coombs’ test. Other: Genital pruritus, vaginitis, candidiasis.
Drug interaction
- Probenecid: Concurrent administration may result in increased and prolonged blood levels of cefalexin by inhibiting renal tubular secretion.
- Nephrotoxic Drugs: (e.g., aminoglycosides, potent diuretics like furosemide) may increase the risk of nephrotoxicity; monitor renal function closely.
- Oral Anticoagulants: (e.g., warfarin) - Cephalosporins have been associated with hypoprothrombinemia and may potentiate the effect of anticoagulants; monitor prothrombin time.
- Metformin: Cefalexin may increase the serum concentration of metformin; careful patient monitoring and potential metformin dose adjustment may be required.
- BCG Vaccine Live / Cholera Vaccine Live: Antibiotics may diminish the therapeutic effect of these live bacterial vaccines.
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. Patients should be advised not to double the dose to make up for a missed one, as this increases the risk of adverse effects.
Overdose
Symptoms of overdose are primarily extensions of the drug’s adverse effects and may include nausea, vomiting, epigastric distress, diarrhea, and hematuria. In cases of significant overdose, particularly in patients with renal impairment, neurotoxicity (e.g., seizures, encephalopathy) may occur. Management is supportive and symptomatic. Gastric lavage may be beneficial if performed soon after ingestion. Cefalexin is efficiently removed from the body by hemodialysis and peritoneal dialysis, which should be considered in severe cases, especially with concomitant renal failure.
Storage
- Store capsules at controlled room temperature, 20°C to 25°C (68°F to 77°F), in a tight, light-resistant container. Protect from moisture.
- Store the constituted oral suspension in a refrigerator (2°C to 8°C / 36°F to 46°F). Do not freeze. Discard any unused portion after 14 days.
- Keep all medications out of the reach of children and pets.
Disclaimer
This information is intended for healthcare professionals and serves as a summary of product characteristics. It is not exhaustive. The prescriber should refer to the full prescribing information for complete details before initiating therapy. The ultimate responsibility for patient care lies with the healthcare professional, considering the patient’s individual circumstances and the most current clinical evidence.
Reviews
“Phexin remains a first-line choice in my practice for uncomplicated SSTIs and strep pharyngitis. Its predictable efficacy, tolerability, and cost-effectiveness make it a reliable workhorse antibiotic. Patient compliance is generally high due to the BID/QID options.” — Dr. Eleanor Vance, Infectious Disease Specialist
“I’ve prescribed the suspension form for pediatric otitis media for years with consistent success. The taste is palatable for children, which is half the battle in ensuring they complete the course. A trusted agent in my formulary.” — Dr. Ben Carter, Pediatrician
“Its spectrum is perfectly suited for community practice. I appreciate the rapid clinical response I see in patients with cystitis, often with symptom resolution within 48 hours. A cornerstone of sensible empiric therapy.” — Dr. Sarah Lim, General Practitioner