Cephalexin

About Cephalexin

Cephalexin kills susceptible bacteria by blocking the building of their cell walls; like other antibiotics, it does not treat viral infections such as the common cold. Its labels cover respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes (the bacterium behind strep throat), middle ear infections, skin and skin structure infections, bone infections, and genitourinary tract infections including acute prostatitis, each caused by susceptible bacteria. Adults and children 15 and older usually take 250 mg every 6 hours or 500 mg every 12 hours, up to 4 g a day in two to four doses for more severe infections, typically for 7 to 14 days. Children over 1 year take 25 to 50 mg/kg a day in divided doses, up to 100 mg/kg a day for severe infections, or 75 to 100 mg/kg a day for middle ear infections. Infections caused by beta-hemolytic streptococci are treated for at least 10 days, and the dose is lowered when kidney function is severely reduced.

There is no boxed warning. Cephalexin must not be taken by anyone allergic to it or to another cephalosporin. Allergic reactions range from rash to anaphylaxis and severe skin reactions, and cross-allergy can occur in people with a history of penicillin allergy, so the prescriber asks about past reactions. Clostridioides difficile diarrhea can follow nearly any antibiotic, even more than two months after the last dose. Cephalosporins have been linked to seizures, mainly in people with kidney impairment whose dose was not reduced, to a positive direct Coombs blood test, and to a prolonged prothrombin time, a measure of clotting. Diarrhea was the most frequent side effect in trials; MedlinePlus also lists nausea, vomiting, heartburn, stomach pain, rectal or genital itching, dizziness and headache.

Cephalexin raises metformin levels, so people who take metformin may need closer monitoring or a dose change. The labels say decades of published data with cephalosporins, including cephalexin, have not established a risk of major birth defects or miscarriage, and that cephalexin is present in human milk. The suspension, which the pharmacy mixes when it is dispensed, comes in 125 and 250 mg per 5 mL and keeps 14 days in the refrigerator. Keflex capsules, including the 333 and 750 mg strengths, are discontinued. MedlinePlus notes that cephalexin is sometimes used before dental or upper respiratory procedures to prevent heart valve infection in people with a heart condition who are allergic to penicillin; that is not an FDA-approved use, and the prescriber decides.

Taking Cephalexin

How to take it

With or without food, usually every 6 or 12 hours for 7 to 14 days, as prescribed; infections caused by beta-hemolytic streptococci need at least 10 days. Shake the liquid well before each dose. Take it until the prescription is finished, even if you feel better; skipping doses or stopping early can make it less effective and make bacteria resistant.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose and carry on as usual. Do not take a double dose.

Storage

Capsules and tablets at room temperature, away from excess heat and moisture (not in the bathroom), out of reach of children. Keep the mixed liquid in the refrigerator, tightly closed, and throw away any left after 14 days.

Interactions to know about

It raises metformin levels, so metformin is monitored and its dose may need adjusting, and probenecid is not recommended with it. It can make a direct Coombs test positive and give false-positive urine glucose results with Benedict’s or Fehling’s solution; MedlinePlus advises Clinistix or TesTape rather than Clinitest.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Cephalexin differs from pharmacy to pharmacy

Cephalexin capsules come from many makers and tablets from few, so quotes for the same course differ by each pharmacy’s fee and markup and by whether cephalexin is on its flat-price generic list. Capsules and tablets are different forms, so the pharmacist fills the one written, and a 500 mg dose written as one capsule or as two 250 mg capsules is quoted as a different quantity.

The suspension is mixed when it is dispensed and quoted by strength and bottle size. A child’s dose is set by weight, so a full course can take more than one bottle, and each mixed bottle keeps 14 days in the refrigerator.

Ways to pay less for Cephalexin without insurance

• Ask whether cephalexin is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• If tablets are prescribed, ask the prescriber whether capsules would suit you as well; the pharmacist cannot switch forms alone.
• For a child’s suspension, ask how many bottles the full course needs, so the quote covers all of it.
• If an older child can swallow capsules, ask the prescriber whether they would suit instead of the liquid.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Cephalexin

1. 1.Is cephalexin safe with my penicillin allergy?
2. 2.Does my kidney function call for a lower dose?
3. 3.Will it affect my metformin or my other medicines?
4. 4.How do I store my child’s liquid, and when do I throw it away?

Related medications