Cephalexin uses, dosage, side effects and interactions

Description and composition of Cephalexin

Cephalexin is a semisynthetic antibacterial antibiotic for oral use in the treatment of bacterial infections.

It is a first generation cephalosporin and contains cephalexin monohydrate.

We have cephalexin capsules, tablets and oral suspension. Apart from these available dosage forms, we equally have different strengths of Cephalexin.

These include:

Cephalexin capsules:

  • 250 mg
  • 500 mg
  • 750 mg

Cephalexin tablets:

  • 250 mg
  • 500 mg

Cephalexin oral suspension

  • 125mg/5ml
  • 250mg/5ml

Uses of Cephalexin

Cephalexin antibiotic is used to treat:

  • Skin/Skin Structure Infections including burns and wound infections
  • Otitis Media
  • Bone Infections
  • Uncomplicated Cystitis
  • Genitourinary Tract Infections
  • Cellulitis and Mastitis
  • Streptococcal Pharyngitis
  • Respiratory Tract Infections
  • Gynaecological and obstetric infections
  • Septicemia

Absorption and excretion of Cephalexin

Cephalexin is acid stable and is rapidly absorbed after oral administration; however, food may delay its absorption.

It is widely distributed throughout the body. Maximum concentration being reached in the liver and kidneys. It does not accumulate following multiple doses; it does not enter the cerebrospinal fluid unless the meninges are inflamed but it does cross the placenta and is secreted in the breast milk 60 to 100% is excreted unchanged in the urine in 8 hours. Small elements are excreted in the bile; probenecid delays renal excretion.

Dosage and administration of Cephalexin

Cephalexin is better administered on an empty stomach as food affects it’s absorption. Take cephalosporin half to 1 hour before meal.


  1. Genitourinary Tract Infections:
    • 250 mg per oral 6 hourly; dosage range, 1-4 g/day in divided doses.
  2. Bone Infections:
    • 250 mg orally 6 hourly; dosage range, 1-4 g/day in divided doses
  3. Skin/Skin Structure Infections 
    • 250 mg orally every 6 hours or 500 mg orally every 12 hours; dosage range, 1-4 g/day in divided doses
  4. Respiratory Tract Infections
    • 250 mg per oral every 6 hour; dosage range, 1-4 g/day in divided doses
  5. Streptococcal Pharyngitis
    • 250 mg orally every 6 hours or 500 mg orally every 12 hours; dosage range, 1-4 g/day in divided doses.
  6. Cellulitis and Mastitis
    • 500 mg per oral every 6 hours; dosage range, 1-4 g/day in divided doses.

Dosage in renal impairment

  • CrCl <10 mL/min: 250-500 mg PO q12-24hr
  • CrCl 10-50 mL/min: 500 mg PO q8-12hr
  • CrCl is creatinine clearance.

Contraindications of Cephalexin

Cephalexin should not be used in individuals who are allergic or hypersensitive to it.

Side effects

The following are the side effects of Cephalexin:

  • Nausea
  • Vomiting
  • Diarrhoea
  • Abdominal pain
  • Allergic reaction
  • Dizziness
  • Fatigue
  • Urticaria
  • Headache
  • Confusion
  • Genital pruritus
  • Angioedema
  • Possibility of pseudo-membraneous colitis exist.

Can a pregnant and breastfeeding women take cephalexin?

You should tell your doctor if you’re pregnant, planning to become pregnant or breastfeeding. Ask your doctor or pharmacist for advice before taking this medicine.

Data from a published clinical lactation study reports that cephalexin is present in human milk; relative infant dose (RID) is considered to be <1% of maternal weight adjusted dose; there are no data on effects of cephalexin on breastfed child or on milk production


It should be used with caution in allergic patients especially when there is a history of penicillin allergy.

How to prepare oral suspension

  1. Shake the bottle to dispense the powder
  2. Add freshly boiled and cooled water a little above powder level; cover tightly and shake firmly.
  3. Add sufficient water up to the mark on the bottle.

How to store

Capsules and tablets: store in a cool dry place, away from sunlight, not exceeding 30ºC.

Powder: the powder should be used stored in a cool dry place, not exceeding 30ºC and away from sunlight. The suspension should be used within 7 days of preparation and stored in a cool place preferably in a refrigerator.

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