Cephalexin: is it an antibiotic? See what it is for and how to use it

The antibiotics are drugs used to combat diseases caused by bacteria, so that the display varies according to the organism causing the problem. This, since it is necessary to use a medicine to which the bacteria is sensitive to action.

There are several antibiotics available in order to treat the most diverse infections, from the most common (throat, ear, urinary) to even the rarest.

Among them is Cephalexin . Understand what it is for, how to use it and the contraindications:

What is Cephalexin?

Cephalexin is a medicinal substance, present as an active ingredient in several medications. It is characterized as an antibiotic, in a way that aims to fight infections caused by bacteria that suffer from its action.

In this sense, it can be indicated for the treatment of conditions such as: pharyngitis (inflammation in the throat), otitis media (ear infection ), urinary tract infection, skin infections etc.

Its duration of action varies depending on the bacteria causing the problem and the severity of the disorder, so it can take only a few days or extend for up to weeks.

The drugs that have Cephalexin as a drug substance are marketed in 3 presentations: tablet, pill, oral suspension and drops. Its liquid forms need to be prepared before use (mix the suspension powder with water).

Although it is a safe medication, tested and approved by ANVISA (National Health Surveillance Agency), it can still have side effects and have contraindications – as for pregnant women, for example.

In this sense, the orientation of using the medicine only under medical prescription is reinforced .

Is it antibiotic?

-Yeah . Cephalexin is, as mentioned, a drug substance classified as an antibiotic. It belongs to the group of cephalosporins, a class of beta-lactam antibiotics (penicillin and its derivatives).

Thus, it is a type of medication used to treat infectious conditions caused by bacteria . In this case, it treats those sensitive to the action of Cephalexin, such as S. pneumoniae (causes otitis, bacterial sinusitis ) or E. coli (causes urinary tract infection).

Its use can only be made by prescription and the prescription is withdrawn at the time of purchase.

What is Cephalexin monohydrate for?

The description “monohydrate” corresponds to the molecular hydration process, which is done in the drugs in order to help them achieve the ideal stability so that they are absorbed and metabolized correctly in the body.

It is a factor that can vary according to each laboratory, so that some remedies can be found in its hydrated and non-hydrated version.

In the case of Cephalexin, it is easily found as a monohydrate in its tablet version, but it is also available in other presentations.

It is important to note that this factor does not change its indication. Therefore, hydrated or not, this medication is an antibiotic indicated for the treatment of diseases caused by bacteria sensitive to the action of Cephalexin. This includes conditions such as:

  • Bacterial sinusitis – caused by streptococcus, S. pneumoniae and Staphylococcus aureus bacteria ;
  • Respiratory tract infections – caused by the bacteria S. pneumoniae and S. pyogenes ;
  • Otitis media (inflammation in the ear) – caused by bacteria S. pneumoniae , H. influenzae , M. catarrhalis , other staphylococci and streptococci;
  • Infections of the skin and soft tissues (blood vessels, muscles, tendons, etc.) – caused by staph bacteria and / or streptococci;
  • Bone infections – caused by staphylococcus and / or P. mirabilis bacteria ;
  • Urinary infections (including acute prostatitis) – caused by the bacteria E. coli , P. mirabilis and Klebsiella pneumoniae ;

It is worth mentioning the fact that Cephalexin is indicated only to treat these conditions when they are caused by bacteria sensitive to their action (as described). What will be analyzed during the medical diagnosis.

Thus, if the problem is not caused by microorganisms that can be combated with this medication, another antibiotic will be prescribed – such as Amoxicillin, for example.

Is it indicated for sore throat?

-Yeah . The package insert indicates the use of Cephalexin to treat infections of the respiratory tract, originated by bacteria such as S. pyogenes , responsible for causing (among other diseases) pharyngitis.

Pharyngitis is a condition that is characterized by pain or irritation in the throat, which can get worse when swallowing saliva or food. This disease can be associated with factors such as colds, climate changes or infections caused by bacteria.

In the case of infection, the use of Cephalexin (or another antibiotic) may be prescribed as a single treatment or in combination with anti-inflammatory drugs to relieve symptoms.

Read more: Pharyngitis: what are the symptoms and treatments?

What is the difference between Amoxicillin and Cephalexin?

Both Amoxicillin and Cephalexin are antibiotics, that is, drugs used to treat conditions caused by bacteria. These are two different remedies that do not necessarily fight the same microorganisms or have the same action.

In this sense, these medications can have different side effects and factors such as drug interaction (effects when and when mixed with other drugs) can also change.

In addition, one can cite as an example the fact that Cephalexin has a maximum daily dose indicated as 4g, while Amoxicillin indicates 6g as the maximum of its dose.

Or, even, the different administration time: it is more common that Cephalexin is prescribed for use every 6 hours, while the administration of Amoxicillin is usually every 12 hours.

These are just a few points where the remedies differ. Although they treat some similar conditions (such as ear infections or sore throats), they are not the same medication and should not be used at the same time or in order to replace one with the other.

How soon does Cephalexin start taking effect?

Considering that Cephalexin is an antibiotic, its effect is intended to prevent the action of bacteria in the body and eliminate them, in order to stop the infection. Therefore, the treatment time can take a few days , but in cases of more resistant infections it can even last for weeks.

The action can also vary depending on the bacteria being fought, so that some can be treated more quickly than others.

In all cases, medical advice should be followed, as interrupting or prolonging treatment on your own can cause other damage to health. Like, for example, bacterial resistance .

In this case, the body acquires resistance to the action of the antibiotic, so that it will not do the desired effects when there is a real need.

Dosage: how to use?

The dosage of Cephalexin, as well as other antibiotics, may vary depending on the infection being treated and its severity. Other factors also contribute to the variations, such as the patient’s age.

In the package insert of the medication, it is possible to find the doses indicated for different conditions (otitis, urinary tract infection, etc.) and the information regarding the predicted dose according to other specific conditions (age, weight, severe cases).

Such content is especially important for the professional, as it serves as a guide and provides safe guidelines that allow you to prescribe the medicine correctly.

Check out some instructions on the package insert regarding Cephalexin presentations (tablet, drops, solution) and understand the forms of use, as well as the doses that can be indicated:

Pill (pill)

According to the information on the package insert, the tablets should be administered orally, regardless of meals, and should not be broken or chewed.

Regarding the dose, the following is indicated:

  • Respiratory tract infections (caused by S. pneumoniae and S. pyogenes ) – a dose of 500mg every 6 hours;
  • Uncomplicated pharyngitis (sore throat), skin infections and cystitis (urinary tract infection) – a dose of 500mg or 1g can be administered every 12 hours, for patients over 15 years old.

The package insert also states that the usual dose for adults is 250mg every 6 hours. And there is an indication of maximum daily dose, being 4g (in fractional doses).

Oral suspension (liquid)

The liquid version of Cephalexin is not marketed ready. Its packaging comes with the powder to prepare the oral suspension, the procedure is as follows:

  • Before opening, shake the bottle to loosen the powder;
  • Put filtered water in the bottle (up to the indicated mark), shake it well so that the powder mixes completely with the water;
  • If this mixture still does not reach the mark indicated on the bottle, wait for the foam to subside and slowly fill with more filter water – then shake again.

That done, the oral suspension is ready. As for the indicated dose, the package insert indicates:

  • Adults – the usual dose is 250mg (2.5mL) every 6 hours, which may be higher in cases of more serious and / or resistant infections;
  • Children – 25 to 50mg / kg (0.25mL to 0.5mL) is recommended in divided doses, but may be higher in cases of severe and / or resistant infections. In addition to changes according to the child’s weight.

The medication should preferably be administered with a syringe. It should be noted that in all cases it is not indicated to exceed 4g daily (maximum dose of the substance).


Just as the oral suspension is not marketed ready, the drop version also needs to be prepared. The preparation is identical in both cases, the difference is only in the size of the bottle: the dropper holds 15mL.

In addition, in this case the package has a dropper type spout.

This presentation is indicated for pediatric use, so that the doses are lower than adult use. Usually, 25mg / kg to 50mg / kg in divided doses is recommended.

In this sense, the package insert has a note: “each drop corresponds to approximately 4.5mg of Cephalexin. Each 1mL of the suspension has approximately 22 drops ”. And it presents the recommended dose based on the child’s weight:

WEIGHT Dose of 25mg / kg Dose of 25mg / kg
Four times a day Twice a day
4 6 drops 11 drops
5 7 drops 14 drops
6 9 drops 17 drops
7 10 drops 20 drops
8 11 drops 22 drops
9 13 drops 25 drops
10 14 drops 28 drops
WEIGHT Dose of 50mg / kg Dose of 50mg / kg
Four times a day Twice a day
4 11 drops 22 drops
5 14 drops 28 drops
6 17 drops 33 drops
7 20 drops 39 drops
8 22 drops 44 drops
9 25 drops 50 drops
10 28 drops 55 drops

Remembering that these indications may change due to the bacterium that causes the disease and the severity of the infection. Following medical recommendations is paramount for safe and effective treatment.

What are the side effects present in the package leaflet?

All medications can cause adverse reactions in those who use them, which does not necessarily mean that this will happen – while some people may suffer from these reactions, others may not have any reactions at all.

In the case of Cephalexin, the label divides the side effects into two groups: those related to gastrointestinal disorders and those that occur due to hypersensitivity to the drug.

Thus, the possible side effects related to the gastrointestinal tract are as follows:

  • Symptoms of pseudomembranous colitis (during or after treatment);
  • Nausea and vomiting (rarely);
  • Diarrhea – indicated on the package insert as the most frequent reaction, but rarely severe enough that it is necessary to stop therapy;
  • Dyspepsia and abdominal pain;
  • Gastritis;
  • Transient hepatitis and cholestatic jaundice (rare).

Therefore, the adverse reactions caused by hypersensitivity to Cephalexin are:

  • Rashes, hives;
  • Angioedema (painless swelling under the skin);
  • Erythema multiforme (immune reaction that occurs rarely);
  • Stevens-Johnson syndrome and toxic epidermal necrolysis (rare manifestations);
  • Anaphylaxis;
  • Itching (anal and genital), genital moniliasis, vaginitis and vaginal discharge;
  • Dizziness, fatigue, headache;
  • Agitation, confusion, hallucinations;
  • Arthralgia (joint pain);
  • Arthritis and joint diseases;
  • Reversible interstitial nephritis (rare renal inflammatory process);
  • Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia and moderate elevations in serum glutamic oxalacetic transaminase (TGO) and serum glutamic-pyruvic transaminase (TGP).

If the patient feels other changes during or after treatment with Cephalexin, a doctor should be consulted in order to diagnose whether the disorder is (or not) related to the use of this medication.

What are the contraindications?

According to the information contained in the package leaflet, Cephalexin is not indicated for people who have already had some sensitivity to penicillins , penicillin derivatives, penicillamine or other cephalosporins.

It should also not be administered to patients with sensitivity or allergy to any component of the formula, especially in the case of the drop version – as some people may have a reaction to the dye.

Can you use it during pregnancy?

The drug substance Cephalexin is classified as risk category B in cases of pregnancy, which means that the drug has not been sufficiently tested in pregnant women. Thus, there is a lack of studies that attest to the safety of use in this population.

Therefore, this medication should only be used based on medical analysis and guidance , considering that its misuse can cause damage to the health of the mother and baby.

What is the price and where to buy?

Medicines that contain Cephalexin as an active ingredient can be purchased at any pharmacy. However, a medical prescription is necessary , since the prescription is mandatory for the sale of antibiotics.

In addition, it is possible to research the price on platforms such as Consulta Remédios , which compares the value of the same product in different stores, to guarantee the lowest.

Next, check the price * of some of the available options:

  • Cephalexin EMS – the box with 10 pills (500mg) costs between R $ 14 and R $ 25;
  • Cephalexin Legrand   – the box with 8 pills (1g) costs between R $ 18 and R $ 33;
  • Keflex – the box with 1 bottle with 100mL of suspension for oral use (50mg / mL) costs around R $ 80;
  • Cephalexin Monohydrate Multilab – the box with 10 pills (500mg) costs between R $ 12 and R $ 28;
  • Cefalexina Oral Suspension União Química – the box with 1 bottle with a capacity of 100mL (50mg / mL) costs between R $ 17 and R $ 29.