What is cephalexin 500 mg used for? Treatment, dosage, and safety tips

In this article:

• What conditions are typically treated with cephalexin 500 mg?
• How does cephalexin work?
• How long does cephalexin take to work?
• Side effects
• What does cephalexin not treat?
• What conditions are typically treated with cephalexin 500 mg?

In this article

• What conditions are typically treated with cephalexin 500 mg?
• How does cephalexin work?
• How long does cephalexin take to work?
• Side effects
• What does cephalexin not treat?
• What conditions are typically treated with cephalexin 500 mg?

One popular antibiotic treatment is cephalexin. Cephalexin is a generic antibiotic sometimes referred to by its brand names Keflex, Daxbia, or Biocef. It’s the medicine of choice for a wide range of bacterial infections, due to its targeted spectrum of activity against common microbes, as well as its overall safety and tolerability. Keep reading below to learn even more about this helpful drug.

Branded Keflex is no longer manufactured, but not due to any safety or efficacy concern. The decision to stop manufacturing the branded formulation was likely a decision made based on a combination of factors, including cost-effectiveness with generic drug availability.

What conditions are typically treated with cephalexin 500 mg?

There are many health conditions that may be treated with cephalexin. Depending on the condition, the dosage of cephalexin could range from 250 mg twice a day to 500 mg four times daily, but 500 mg of cephalexin every 12 hours is typically an effective strength for a variety of treatments.

“In my general medical practice, I frequently prescribe Cephalexin for skin infections, minor respiratory infections, and post-surgical wound prophylaxis when appropriate,” said Dr. Martina Ambardjieva, a urologist and practicing medical doctor in Washington State.

There is a large list of possible uses for the drug. Use of this medication may be prescribed for the treatment of the following infections:

Soft tissue and skin structure infections

Cephalexin can treat the 2 top bacterial causes for skin and soft tissue infections like cellulitis, impetigo, folliculitis, and boils–Staphylococcus aureus and Streptococcus pyogenes. Gram-negative bacteria are less likely to cause these types of infections, but cephalexin may have some limited activity in that clinical setting. 

Respiratory tract infections 

Cephalexin can treat some types of pneumonia and types of upper respiratory tract infections like pharyngitis (sore throat) or bacterial rhinosinusitis. It can also treat more serious cases of strep throat that develop into scarlet fever.

Urinary tract infections (UTIs)

Infections of the kidneys, ureters, bladder, and urethra may also be treated with Cephalexin. Dr. Ambardjiev explained, “In my urology practice, Cephalexin is often used to treat uncomplicated UTIs, especially when first-line resistance is a concern or when patients have a history of mild penicillin allergies.”

Ear infections

Cephalexin has been FDA-approved for the treatment of otitis media, more commonly known as an ear infection, caused by certain types of bacteria.

Strep Throat

Streptococcus pyogenes is also a leading cause of pharyngitis and tonsillitis in adolescents and young children, commonly referred to as strep throat. Cephalexin for strep throat is not a first-line regimen, but can be effective for individuals unable to tolerate those first line antibiotics.

Other infections

Cephalexin may also be prescribed to treat certain bone infections, prevention or treatment of surgical site infections, and dental issues, including gum infections or dental abscesses.

How does cephalexin work?

Cephalexin belongs to a class of medications called cephalosporin antibiotics. These medications inhibit normal bacterial activity, causing bacteria to die. 

Simply put, cephalexin kills off the bacteria causing an infection. For a more technical explanation, cephalexin interrupts the synthesis of bacterial cell walls, causing the bacteria to break down.

How long does cephalexin take to work? 

Cephalexin is sold as an oral capsule or tablet and can be stored at room temperature. It is also available as a liquid medicine in the form of an oral suspension, commonly employed for pediatric patients or those with difficulty swallowing solid dosage forms. Cephalexin will begin working on the bacteria within an hour of treatment, but the symptoms take longer to dissipate. 

“Clinical improvement in symptoms typically begins within 48 to 72 hours, although full resolution depends on the infection type and severity,” explained Dr. Ambardjieva.

The dosage and time frame you take cephalexin will depend on the type of infection and the severity of the condition. The oral capsule is available in strengths of 250 mg, 500 mg, and 750 mg. For patients over 15 years old, the standard cephalexin dosage is 250 mg taken every 6 hours or 500 mg taken every 12 hours. However, variations from this dosage are anticipated, as both patient characteristics and infection characteristics are taken into account by prescribers. The length of time someone will take cephalexin usually ranges from 7 to 14 days.

If you miss a dose, take it as soon as possible. If your next dose is scheduled soon, continue the treatment with that dose.

Side effects of cephalexin

“Cephalexin is safe for most adults and children, but there are side effects that may occur when taking the medication,” said Lindsey Hudson, a board-certified family nurse practitioner in Charleston, South Carolina.

Those with certain medical conditions, like kidney problems and a history of hypersensitivity reactions, which are severe allergic reactions,to certain antibacterial drugs, should also use caution before taking the prescription. A healthcare professional can provide medical advice about the risks for your particular situation before starting the treatment.

As with any medication, side effects may be experienced when taking it. Common side effects of cephalexin may include:

• Nausea 
• Abdominal pain
• Vomiting 
• Diarrhea 
• Rash 
• Headache 
• Dizziness

Others may experience serious side effects of cephalexin. While rare, they may include:

• Anaphylaxis, or a severe allergic reaction
• Swelling of the face 
• Difficulty breathing
• Hives
• Stevens-Johnson syndrome, a serious condition characterized by flu-like symptoms, rash, and blisters
• Hemolytic anemia, which is diagnosed through lab tests

If you experience any of these critical adverse reactions, seek immediate medical attention.

You can learn more information about adverse effects, drug interactions, and precautions about cephalexin here. 

If you have more concerns, your healthcare provider or pharmacist can help by answering any questions you may have about cephalexin therapy and possible side effects. Be sure to share your complete medical history and provide a list of medications and supplements you take. 

What does cephalexin not treat?

Cephalexin only treats infections caused by certain types of bacteria. Some bacteria are unaffected by cephalexin, as well as other types of infections and conditions it cannot treat, like viral infections. This may include:

• Viruses that cause the common cold, like rhinovirus or enterovirus
• Influenza
• Infections caused by methicillin-resistant Staphylococcus aureus (MRSA)
• Infections caused by Enterococcus species
• Infections caused by Pseudomonas aeruginosa
• Infections caused by Enterobacter spp., Morganella morganii, Proteus vulgaris, and most strains of Acinetobacter​.

Another factor to consider with antibiotics is antibiotic resistance. Sometimes, bacteria adapt to the antibiotic and require a different prescription for treatment. This can also become a problem for patients with a more severe infection. In these cases, laboratory tests or other medical tests can be given to find the best drug treatment. If it is taking a longer time to recover from an infection than expected, seek medical help, as an alternative prescription drug may be needed.

“In urological practice, if complicated UTIs or infections caused by multidrug-resistant organisms are suspected, broader-spectrum antibiotics or culture-specific treatments are preferred,” said Dr. Ambardjieva.

Whatever infection you’re facing, speak with your healthcare provider for their medical advice about the best treatment options. They can go over all your best options, which may include cephalexin.