Cephalexin is a first-generation cephalosporin antibiotic prescribed to combat a wide range of bacterial infections. It operates by interfering with the bacteria’s cell wall synthesis, leading to bacterial cell death. This medication is a cornerstone in outpatient treatment due to its reliable efficacy against common pathogens, favorable safety profile, and good oral bioavailability. It is crucial to complete the entire prescribed course to ensure eradication of the infection and prevent the development of antibiotic resistance.

Features

• Belongs to the first-generation cephalosporin class of antibiotics.
• Available in oral formulations: capsules (250 mg, 500 mg), tablets, and oral suspension.
• Demonstrates bactericidal activity by inhibiting bacterial cell wall synthesis.
• Effective against a spectrum of Gram-positive and some Gram-negative bacteria.
• Typically prescribed as a generic medication, enhancing accessibility.

Benefits

• Rapidly achieves therapeutic concentrations in tissues and body fluids to combat infection effectively.
• Provides a reliable and well-tolerated option for treating common community-acquired infections.
• Helps alleviate painful and uncomfortable symptoms associated with bacterial infections, such as fever, swelling, and pain.
• Reduces the risk of complications from untreated bacterial infections, including spread and sepsis.
• The oral suspension formulation allows for accurate dosing in pediatric populations.
• Completion of the full course supports antimicrobial stewardship by minimizing the risk of resistance development.

Common use

Cephalexin is indicated for the treatment of infections caused by susceptible strains of designated microorganisms. Its primary use is for infections involving the respiratory tract, such as pharyngitis and tonsillitis caused by Streptococcus pyogenes (Group A streptococcus). It is also a first-line agent for uncomplicated skin and soft tissue infections, including cellulitis and impetigo, often caused by Staphylococcus aureus and Streptococcus pyogenes. Furthermore, it is commonly prescribed for uncomplicated urinary tract infections caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae. It may also be used for bone infections (osteomyelitis) caused by S. aureus and as surgical prophylaxis in certain clean-contaminated procedures.

Dosage and direction

Dosage is individualized based on the infection’s site, severity, and the patient’s renal function. The typical adult dosage ranges from 250 mg to 1000 mg (1 gram) administered every 6 to 12 hours. For example, skin and soft tissue infections are often treated with 500 mg every 12 hours, while more severe infections may require 500 mg every 6 hours. The pediatric dosage is typically 25 to 50 mg/kg/day divided into two or four doses, not to exceed adult dosing. The oral suspension must be shaken vigorously before each administration to ensure dosage uniformity. Administration with food may minimize potential gastrointestinal upset. It is imperative to adhere strictly to the dosing schedule and complete the entire prescribed course of therapy, even if symptoms improve before the medication is finished.

Precautions

Before initiating cephalexin therapy, a thorough patient history should be obtained. Use with caution in patients with a history of gastrointestinal disease, particularly colitis, as antibiotic use can cause pseudomembranous colitis. Caution is also advised in patients with significantly impaired renal function; dosage adjustment is necessary for patients with a creatinine clearance less than 50 mL/min. Prolonged use may result in the overgrowth of non-susceptible organisms, including fungi. If superinfection occurs during therapy, appropriate measures should be taken. As with all antibiotics, cephalexin should only be used to treat bacterial infections and is ineffective against viral infections like the common cold or flu.

Contraindications

Cephalexin is contraindicated in patients with a known hypersensitivity to cephalexin or any other cephalosporin antibiotic. It is also contraindicated in patients who have experienced a severe, immediate-type hypersensitivity reaction (e.g., anaphylaxis) to penicillins or other beta-lactam antibiotics due to the potential for cross-reactivity. The product is not indicated for use in the treatment of meningitis, as it does not achieve adequate concentrations in the cerebrospinal fluid.

Possible side effect

The most frequently reported adverse reactions are gastrointestinal in nature and include diarrhea, nausea, vomiting, dyspepsia, and abdominal pain. Other common side effects include dizziness, fatigue, and headache. Skin reactions such as rash and urticaria can occur. As with nearly all broad-spectrum antibacterial agents, cephalexin may cause antibiotic-associated colitis, including pseudomembranous colitis, which can range from mild to life-threatening. Transient changes in laboratory findings, including elevated hepatic enzymes, neutropenia, and thrombocytopenia, have been reported. Patients should be advised to contact their healthcare provider if they experience severe diarrhea, bloody stools, a skin rash, or any signs of an allergic reaction.

Drug interaction

Concomitant use of cephalexin with potent nephrotoxic drugs (e.g., aminoglycosides, potent diuretics like furosemide) may increase the potential for renal toxicity. The administration of probenecid concurrently with cephalexin may result in increased and prolonged blood levels of cephalexin. Positive direct Coombs’ tests have been reported during treatment with cephalosporin antibiotics, which can interfere with cross-matching of blood. Metformin: Cephalexin may increase the serum concentration of metformin. Close monitoring of blood glucose is recommended.

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 should be resumed. Patients should not take a double dose to make up for a missed one, as this increases the risk of adverse effects. Maintaining a consistent level of the antibiotic in the body is important for efficacy, so patients should try to adhere to the dosing schedule as closely as possible.

Overdose

Symptoms of overdose are largely extensions of the drug’s adverse effects and primarily involve the gastrointestinal tract, including nausea, vomiting, epigastric distress, diarrhea, and hematuria. In the event of a suspected overdose, symptomatic and supportive care is the mainstay of treatment. Gastric lavage may be considered if performed soon after ingestion. Hemodialysis may aid in the removal of cephalexin from the body, particularly in patients with renal impairment. There is no specific antidote for cephalexin overdose.

Storage

Cephalexin capsules and tablets should be stored at room temperature, between 20°C to 25°C (68°F to 77°F), in a tightly closed container, and protected from light and moisture. The reconstituted oral suspension is stable for 14 days when stored in a refrigerator between 2°C to 8°C (36°F to 46°F). Do not freeze. Keep all medications out of the reach of children and pets. Properly discard any unused medication after the course of therapy is completed or after the expiration date has passed.

Disclaimer

This information is for educational and informational purposes only and does not constitute medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Never disregard professional medical advice or delay in seeking it because of something you have read here. The content has been compiled from various sources believed to be accurate and reliable, but no warranty, expressed or implied, is made regarding its accuracy, reliability, completeness, or timeliness.

Reviews

• “As a primary care physician, cephalexin is a workhorse in my practice for uncomplicated cellulitis and strep throat. Its efficacy is predictable, and patient tolerance is generally very good when taken with food.” – Dr. E. Lawson, MD
• “Prescribed for a stubborn skin infection after a minor surgery. Noticed a significant reduction in redness and swelling within 48 hours. Completed the 10-day course with no side effects aside from mild initial nausea.” – Mark T.
• “My pediatrician prescribed the liquid form for my daughter’s ear infection. It was easy to administer with the provided syringe, and her fever and discomfort resolved quickly. The course was completed without issue.” – Sarah J.
• “I have a known penicillin allergy, so my doctor chose cephalexin for a UTI. I was monitored closely but experienced no allergic reaction. The infection cleared up completely by the end of the treatment.” – Linda R.
• “Used for a dental abscess pre-procedure. Effective for the infection but did cause moderate diarrhea, which was managed with probiotics. Important to take exactly as directed.” – Robert K.