Cephalexin Uses, Dosage, Side Effects, Food Interaction and all others data.

Cephalexin is a semisynthetic analogue of Cephalosporin C. It kills bacteria by interfering in the synthesis of the bacterial cell wall. Peptidoglycan is a heteropolymeric structure that provides the cell wall with mechanical stability. The final stage in the synthesis of peptidoglycan involves the completion of the cross-linking and the terminal glycine residue of the Pentaglycine Bridge is linked to the fourth residue of the pentapeptide (d-alanin). The transpeptidase enzyme that performs this step is inhibited by penicillins and cephalosporins. As a result the bacterial cell wall is weakened, the cell swells and then ruptures. Cephalexin is a first generation cephalosporin that is active by mouth.

Cephalexin (also called Cefalexin) is a first generation cephalosporin antibiotic. It is one of the most widely prescribed antibiotics, often used for the treatment of superficial infections that result as complications of minor wounds or lacerations. It is effective against most gram-positive bacteria through its inihibition of the cross linking reaction between N-acetyl muramicacid and N-acetylglucosamine in the cell wall, leading to cell lysis.

Trade Name Cephalexin
Availability Prescription only
Generic Cephalexin
Cephalexin Other Names Cefalexin, Cefalexina, Céfalexine, Cefalexinum
Related Drugs amoxicillin, prednisone, doxycycline, ciprofloxacin, metronidazole, azithromycin, clindamycin, ceftriaxone, levofloxacin, Augmentin
Weight 250mg, 500mg, 125mg/5ml, , 750mg, 250mg/5ml
Type Capsule, Powder For Suspension, Oral Capsule, Oral Powder For Reconstitution, Oral Tablet
Formula C16H17N3O4S
Weight Average: 347.389
Monoisotopic: 347.093976737
Protein binding

Cephalexin is 10-15% bound to serum proteins including serum albumin.[A179053]

Groups Approved, Investigational, Vet approved
Therapeutic Class First generation Cephalosporins
Manufacturer Essential Drugs Company Ltd
Available Country Bangladesh, Canada, United States
Last Updated: September 19, 2023 at 7:00 am


Cephalexin is used for the treatment of the following infections when caused by susceptible organisms.

  • Respiratory tract infections: Acute and chronic bronchitis and infected bronchiectasis.
  • Genito-urinary tract infections: Acute and chronic nephritis, cystitis, urethritis and prostatitis, prophylaxis of recurrent urinary tract infections.
  • Skin and soft tissue infections: Caused by staphylococci and/or streptococci.
  • Ear, Nose and Throat infections: Otitis media, mastoiditis, sinusitis, follicular tonsillitis and pharyngitis.
  • Bone infections: Caused by staphylococci and/or P. mirabilis.

Cephalexin is also used to associated treatment for these conditions: Bone Infection, Genitourinary tract infection, Otitis Media (OM), Respiratory Tract Infections (RTI), Skin and skin structure infections, Acute Prostatitis

How Cephalexin works

Cephalexin is a first generation cephalosporin antibiotic. Cephalosporins contain a beta lactam and dihydrothiazide. Unlike penicillins, cephalosprins are more resistant to the action of beta lactamase. Cephalexin inhibits bacterial cell wall synthesis, leading breakdown and eventualy cell death.


Cephalexin dosage


  • The usual dose is 250 mg to 500 mg every 6 hour.
  • For skin and soft tissue infections, streptococcal pharyngitis and uncomplicated cystitis, in patients over 15 years of age: 500 mg of the drug may be administered every 12 hour.
  • In severe or deep seated infections the dose can be increased up to 3 g to 6 g daily.

Children: The dosage range is 25-100 mg/kg/day in divided doses to a maximum of 4 g dailyChildren's Weight Recommended Dose:

  • 10 kg (22 Ibs):62.5 mg to 125 mg qid or 125 mg to 250 mg bid
  • 20 kg (44 Ibs):125 mg to 250 mg qid or 250 mg to 500 mg bid
  • 40 kg (88 Ibs):250 mg to 500 mg qid or 500 mg to 1 g bid

For streptococcal pharyngitis, skin and soft tissue infections and in patients over 1 year of age the total daily dose may be divided and administered every 12 hour. In the therapy of otitis media 75-100 mg/kg/day in four divided doses may be required. In the treatment of β haemolytic streptococcal infections a therapeutic dosage of the drug should be given at least for 10 days.

Side Effects

Side effects include nausea, vomiting, diarrhoea and abdominal discomfort. Symptoms of pseudomembranous colitis may appear either during or after antibiotic treatment. Skin rash, angio oedema, rise in serum aminotransferases, eosinophilia, neutropenia have been reported very rarely. Superinfection with resistant micro organisms, particularly candida may follow the treatment.


Symptoms of overdose include blood in the urine, diarrhea, nausea, upper abdominal pain, and vomiting. An overdose is generally managed through supportive treatment as diuresis, dialysis, hemodialysis, and charcoal hemoperfusion are not well studied in this case.

The oral median lethal dose of cephalexin in rats is >5000 mg/kg. The oral LD50 in a monkey is >1g/kg and the lowest dose causing a toxic effect in humans is 14mg/kg.

Cephalexin has not been shown to be harmful in pregnancy and is not associated with teratogeniticy. Cephalexin is present in breast milk, though infants may be exposed to Label The effects of breast milk exposure to cephalexin have not been established and so caution must be exercised and the risk and benefit of cephalexin use in breastfeeding must be weighed.

Cephalexin has not been studied for carcinogenicity or mutagenicity. Cephalexin has no affect on fertility in rats.


Cefalexin should be given with caution in patients with renal impairment. Under such condition, careful clinical observation should be made because safe dosage may be lower than the usually recommended. The urine of patients receiving Cefalexin may give a false positive reaction for glucose with copper reduction reagent. Positive results to Coombs’ test have been reported. Although there is no evidence of teratogenicity in animal tests, Cefalexin may be used during pregnancy when it is considered essential. Cefalexin is found in the milk of nursing mothers, hence caution should be taken when it is administered to nursing mothers.

Food Interaction

  • Take with or without food.

Cephalexin multivitamins interaction

[Moderate] ADJUST DOSING INTERVAL: Oral products containing zinc such as mineral supplements and multivitamins may interfere with the gastrointestinal absorption of cephalexin, ceftibuten or cephradine.

In one pharmacokinetic study (n=12), concurrent administration of zinc sulfate (250 mg, single oral dose) and cephalexin (500 mg, single oral dose) decreased cephalexin maximum concentration (Cmax) and systemic exposure (AUC; 0-inf) by 31.05% and 27.4%, respectively.

However, in the same study, when zinc sulfate was administered 3 hours after the cephalexin dose, no significant alteration in cephalexin pharmacokinetics were observed.

Oral medications or mineral supplements that contain zinc are recommended to be administered at least 3 hours after the cephalexin, ceftibuten or cephradine dose.

Volume of Distribution


Elimination Route

Well absorbed from the upper gastrointestinal tract with nearly 100% oral bioavailability. Cephalexin is not absorbed in the stomach but is absorbed in the upper intestine.

Patients taking 250mg of cephalexin reach a maximum plasma concentration of 7.7mcg/mL and patients taking 500mg reach 12.3mcg/mL.

Half Life

The half life of cephalexin is 49.5 minutes in a fasted state and 76.5 minutes with food though these times were not significantly different in the study.


Clearance from one subject was 376mL/min.

Elimination Route

Cephalexin is over 90% excreted in the urine after 6 hours by glomerular filtration and tubular secretion with a mean urinary recovery of 99.3%. Cephalexin is unchanged in the urine.

Pregnancy & Breastfeeding use

Pregnancy Category B. Cefalexin may be used during pregnancy when it is considered essential. Cefalexin is found in the milk of nursing mothers, hence caution should be taken when it is administered to nursing mothers.


Cephalen is contraindicated in patients with known hypersensitivity to the cephalosporin group of antibiotics.

Storage Condition

Should be stored in cool and dry place.

Innovators Monograph

You find simplified version here Cephalexin

Cephalexin contains Cephalexin see full prescribing information from innovator Cephalexin Monograph, Cephalexin MSDS, Cephalexin FDA label


What Cephalexin is used for?

Cephalexin is used to treat bacterial infections in many different parts of the body. It belongs to the class of medicines known as cephalosporin antibiotics. It works by killing bacteria or preventing their growth. However, this medicine will not work for colds, flu, or other virus infections.

How safe is Cephalexin?

Cephalexin is not suitable for some people. To make sure Cephalexin is safe for you, tell your doctor if you have an allergic reaction to Cephalexin or any other medicine in the past.

How does Cephalexin work?

Cephalexin works by interfering with the formation of the bacteria's cell walls. This ruptures the walls and kills the bacteria.Cephalexin should only be used to treat bacterial infections. You should not use it to treat viruses, such as the common cold.

Is Cephalexin safe during pregnancy?

Cephalexin usually safe to take Cephalexin during pregnancy and while breastfeeding.

Is Cephalexin safe during breastfeeding?

Cephalexin is acceptable for nursing mothers.

Can I drink alcohol with Cephalexin?

You can drink alcohol while taking Cephalexin. It's important to keep taking Cephalexin until you've completed the course, even if you feel better.

Can I drive while taking Cephalexin?

Cephalexin generally does not cause any problems with your ability to drive a car or operate machinery. 

Does Cephalexin make me sleepy?

Cephalexin oral capsule doesn't cause drowsiness. However, it can cause other side effects.

When is the best time to take Cephalexin?

Cephalexin is usually taken with or without food every 6 or 12 hours for 7 to 14 days, depending on the condition being treated. Take Cephalexin at around the same times every day.

How long does Cephalexin take to work?

Peak concentrations of Cephalexin are reached one hour after dosing; however, it may take up to 48 hours before infection-related symptoms start to abate.

Should Cephalexin be taken with food?

Although it may be absorbed more quickly if it is taken on an empty stomach, Cephalexin may be taken with food or on an empty stomach. The overall effect is not changed by taking it with food.

Who should not take Cephalexin?

You should not use this medicine if you are allergic to Cephalexin or to similar antibiotics, such as Ceftin, Cefzil, Omnicef, and others. Tell your doctor if you are allergic to any drugs, especially penicillins or other antibiotics.

What happens if I miss a dose of Cephalexin?

Take Cephalexin as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose of Cephalexin?

Seek emergency medical attention .Overdose symptoms may include nausea, vomiting, stomach pain, diarrhea, and blood in your urine.

Can I take Cephalexin for a long time?

Continue to take Cephalexin until you finish the prescription even if you feel better. If you stop taking Cephalexin too soon or skip doses, your infection may not be completely treated and the bacteria may become resistant to antibiotics.

How long does it take for antibiotics to leave my body?

Each antibiotic may stay in the body for different lengths of time, but common antibiotics such as amoxicillin and Cephalexin stay in your system for about 24 hours after taking the last dose. It might take longer for people with impaired kidney function to eliminate the drug from the body.

*** Taking medicines without doctor's advice can cause long-term problems.