Cefalexin + Lactobacillus

Usage

Cefalexin is a first-generation cephalosporin antibiotic used to treat bacterial infections. Lactobacillus, a probiotic, is sometimes used concurrently with antibiotics to help prevent antibiotic-associated diarrhea. This combination is not a fixed-dose combination product; they are prescribed and administered separately.

Pharmacological Classification:

• Cefalexin: Antibiotic, first-generation cephalosporin
• Lactobacillus: Probiotic

Mechanism of Action:

• Cefalexin: Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to bacterial cell death.
• Lactobacillus: Helps restore the balance of gut microbiota, which can be disrupted by antibiotics, reducing the risk of antibiotic-associated diarrhea.

Alternate Names

Cefalexin: Ceporex, Keflex (brand name), Cephalexin Monohydrate

Lactobacillus: Various species exist (e.g., Lactobacillus acidophilus, Lactobacillus rhamnosus) and are often included in probiotic formulations under various brand names.

How It Works

Cefalexin:

• Pharmacodynamics: Bactericidal action by disrupting bacterial cell wall synthesis.
• Pharmacokinetics:
  • Well-absorbed orally.
  • Primarily excreted unchanged in urine via glomerular filtration and tubular secretion.
  • Half-life is approximately 1 hour.
  • Food may slightly decrease the rate but not the extent of absorption.

Lactobacillus:

• Pharmacodynamics: Improves gut microbial balance, reduces inflammation, and enhances gut barrier function.
• Pharmacokinetics:
  • Not systematically absorbed.
  • Colonizes the gastrointestinal tract.

Dosage

Cefalexin:

Standard Dosage

Adults:

• 250-500 mg every 6-12 hours, depending on infection severity.
• Maximum daily dose is 4g.
• Duration of therapy: 7-14 days, or as directed by a physician.

Children:

• 25-100 mg/kg/day, divided into 2-4 doses.
• Dosage depends on age, weight, and infection severity.

Special Cases:

• Elderly Patients: Dosage adjustment may be necessary for those with renal impairment.
• Patients with Renal Impairment: Dose reduction based on creatinine clearance (CrCl). See below.
• Patients with Hepatic Dysfunction: No specific dosage adjustments are generally needed.
• Patients with Comorbid Conditions: Dosage adjustments might be required. Consult a physician.

Lactobacillus:

Administered separately, as per the probiotic product’s instructions. Dosage varies across formulations.

Clinical Use Cases

Dosing for Cefalexin remains the same as standard dosing. For surgical prophylaxis, a single dose may be administered before the procedure.

Dosage Adjustments

Cefalexin:

• Renal Impairment:
  • CrCl ≥50 mL/min: No adjustment.
  • CrCl 30-59 mL/min: Maximum daily dose should not exceed 1g.
  • CrCl 15-29 mL/min: 250 mg every 8-12 hours.
  • CrCl 5-14 mL/min: 250 mg every 24 hours.
  • CrCl 1-4 mL/min: 250 mg every 24-60 hours.
  • Hemodialysis: Administer dose after dialysis.

Side Effects

Cefalexin:

Common Side Effects

• Diarrhea, nausea, vomiting, abdominal pain, rash, pruritus, headache.

Rare but Serious Side Effects:

• Clostridium difficile associated diarrhea, Stevens-Johnson syndrome, toxic epidermal necrolysis, serum sickness-like reaction, anaphylaxis, hemolytic anemia, thrombocytopenia.

Contraindications

Cefalexin:

• Hypersensitivity to cephalosporins or penicillins.

Drug Interactions

Cefalexin:

• Probenecid: Reduces renal excretion of cefalexin, increasing its serum levels.
• Oral contraceptives: Efficacy may be reduced.
• Metformin: Cefalexin can increase metformin levels.

Pregnancy and Breastfeeding

Cefalexin:

• Pregnancy Category B. Generally considered safe.
• Excreted in breast milk, monitor infant for diarrhea.

Lactobacillus: Generally considered safe during pregnancy and breastfeeding.

Drug Profile Summary

Please refer to the sections above.

Popular Combinations

Cefalexin is often used alone. Concomitant use with Lactobacillus is not a standard “combination therapy”, rather, it is supplemental to mitigate potential side effects of antibiotic usage.

Precautions

Please refer to the sections above.

FAQs

Q1: What is the recommended dosage for Cefalexin + Lactobacillus?

A: Cefalexin and Lactobacillus are dosed separately. Refer to dosage instructions specific to the prescribed probiotic product. Cefalexin adult doses range from 250 mg every 6 hours to 500mg every 12 hours, with a maximum of 4g/day. Pediatric doses are based on weight (25-100 mg/kg/day).

Q2: Can Cefalexin be used in patients with penicillin allergy?

A: Caution is advised. Some patients with penicillin allergy may also be allergic to cephalosporins (cross-reactivity).

Q3: What are the signs of a serious allergic reaction to Cefalexin?

A: Difficulty breathing, swelling of the face, lips, or tongue, hives, severe rash, rapid heartbeat, dizziness.

Q4: What are the common side effects of Lactobacillus?

A: Mild gas and bloating.

Q5: How does Lactobacillus prevent antibiotic-associated diarrhea?

A: It helps maintain the balance of gut flora and reduce the overgrowth of C. difficile.

Q6: Can Cefalexin be used during pregnancy?

A: Generally considered safe, but consult a physician.

Q7: What should I do if I miss a dose of Cefalexin?

A: Take the missed dose as soon as possible. If it is near the time for the next dose, skip the missed dose and return to your regular schedule.

Q8: Can Cefalexin be crushed or chewed?

A: Capsules and tablets should be swallowed whole. Liquid formulations are available.

Q9: How should Cefalexin be stored?

A: Store at room temperature away from excessive heat and moisture. Liquid formulations might require refrigeration.

Q10: What are the typical durations of therapy for Cefalexin?

A: Usually 7-14 days, but this may vary based on the infection and the prescribing physician’s clinical judgement.