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 of cephalexin
• What does cephalexin not treat?

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 of cephalexin
• What does cephalexin not treat?

Since the discovery of antibiotics in 1928, numerous infection-fighting medicines have hit the market. Many people are familiar with penicillin antibiotics, the first one to be mass-produced, but that’s not your only option. 

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

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. Cephalexin may be prescribed for the treatment of the following infections:

• Soft tissue and skin structure infections: Cephalexin can treat Staphylococcus aureus bacteria, which cause staph infections. It can also combat Streptococcus pyogenes bacteria, the leading cause of pharyngitis and tonsillitis in adolescents and young children, commonly referred to as strep throat.
• Respiratory tract infections: Cephalexin can treat some types of pneumonia. 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.
• 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 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 250 mg, 500 mg, and 750 mg strengths. For patients over 15 years old, the standard cephalexin dosage will be 250 mg taken every 6 hours or 500 mg taken every 12 hours, although variation from this is anticipated as both characteristics of the patient and the infection are taken into account by prescribers. The length of time someone will take cephalexin usually ranges from 7 to 14 days.

If you have a missed dose, take it as soon as possible, or continue the treatment with your next dose if it’s scheduled soon.

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 or 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, there are side effects that 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

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 health care 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.

“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.