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Is QID dosing necessary for cephalexin?

Nearly every guideline or reference source quotes four times daily dosing. That’s four times a day! How challenging is it to get patients to take daily medications, let alone something dosed four times a day? I’m skeptical of the feasibility of this dosing regimen...

Is BID dosing as effective as QID? However, the single study available suggests equivalence. Therefore, for simplicity and ease of use, I will offer my patients 1g BID cephalexin x 5 days for the treatment of uncomplicated cellulitis.

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 Cephalexin – You Are My Only One for Uncomplicated Cellulitis

Among patients with uncomplicated cellulitis, the use of cephalexin plus TMP-SMX compared to cephalexin alone did not result in higher rates of clinical resolution of cellulitis in the per-protocol analysis. However, because imprecision around the findings in the modified intention-to-treat analysis included a clinically important difference favoring cephalexin plus TMP-SMX, further research may be needed.

 Mythbuster: The 10% cephalosporin-penicillin cross-reactivity risk

The true incidence of an allergy to penicillin in patients believed to have such allergy is <10% (it’s like we have a built in 10-fold safety factor). Cross-reactivity between penicillins and MOST 1st and 2nd generation cephalosporins is negligible. Cross-reactivity between penicillins and ALL 3rd and 4th generation cephalosporins is negligible. If a patient has an allergy to amoxicillin or ampicillin, avoid cefadroxil, cefaclor, cefatrizine, cefprozil, cephalexin, and cephradine.

Articles of Interest

Cephalexin vs Amoxicillin: Everything You Need to Know

Cephalexin and amoxicillin are common beta-lactam antibiotics. Both are broad-spectrum antibiotics, meaning they work against a wide range of bacteria. They are often used to treat similar types of bacterial infections, but they are not the same.

A Critical Review of Cephalexin and Cefadroxil for the Treatment of Acute Uncomplicated Lower Urinary Tract Infection in the Era of "Bad Bugs, Few Drugs"

First-generation oral cephalosporins (cephalexin and cefadroxil) have traditionally been considered second-line treatment options for uncomplicated lower urinary tract infections (uLUTIs). However, in the current age of "bad bugs, few drugs", where there are increasingly limited oral options against resistant Enterobacteriaceae, there is an urgent need to rethink how best to utilize the available antibiotic armamentarium.

Cephalexin Remains Preferred Oral Antibiotic Therapy for Uncomplicated Cellulitis

Even in the community-acquired MRSA era, cephalexin should remain the mainstay of oral antibiotic therapy for uncomplicated cellulitis. Cephalexin should be optimally dosed, that is, 1 g (PO) q6h, and be the mainstay of IV-to-PO switch programs for hospital patients with uncomplicated cellulitis being treated with β-lactams parenterally.

Cephalexin Should Not Be Used for UTIs Without Confirming Susceptibility

Many would argue that cephalosporins, specifically first-generation cephalosporins like cephalexin, are optimal agents for UTI. Generally speaking, their spectrum of activity is predominantly gram-positive organisms with sporadic coverage of Enterobacteriaceae including Escherichia coli, Klebsiella species, and Proteus mirabilis. Considering spectrum of activity, cephalexin does not appear to be a logical choice, but let's review the evidence. Consider sulfamethoxazole/trimethoprim or nitrofurantoin per the IDSA guidelines along with second- (e.g., cefuroxime) or third-generation (e.g., cefdinir or cefpodoxime) cephalosporins for empiric treatment of uUTIs. Cephalexin every six or eight hours is an appropriate and narrow choice of antibiotic if culture and sensitivity data are available.

Everything You Need To Know About Using Keflex Antibiotics

Keflex is a broad-spectrum antibiotic that is effective across many bacteria. It has excellent activity against streptococcus pneumonia, staphylococcus aureus, S. pyrogens, Proteus mirabilis, and Moraxella catarrhalis. Even better, the effect of Keflex kicks in one hour after you take it. However, you could take up to 48 hours to see the results.

High-dose cephalexin for cellulitis: a pilot randomized controlled trial

High-dose cephalexin had fewer treatment failures but with a higher proportion of minor adverse effects. The findings of this trial will be used to optimize the design of a future definitive trial.

Initial Antibiotic Choice in Uncomplicated Cellulitis

In patients with cellulitis and no evidence of abscess who are well appearing without signs of systemic infection, it is reasonable to treat with antibiotics covering streptococci and not adding coverage for MRSA initially (i.e. cephalexin alone). Patients should be given follow up and good instructions for return visit for treatment failure.

Penicillin-Cephalosporin Cross-Reactivity Made Easy

The cross-reactivity between cephalosporins and penicillins is significantly lower than the 10% figure many of us learned. In fact, the beta-lactam ring is rarely involved. So, when the warning pops up next time you order ceftriaxone in a penicillin-allergic patient, what should you do?

What Should I Avoid While Taking Cephalexin (Keflex)?

If you are taking cephalexin, there are some foods you might want to avoid. Some of these can cause interactions with the medication, while others can increase the side effects.

What Should I Not Take With Cephalexin?

If you do a quick internet search on the drug, you’ll see a laundry list of potentially problematic medications and supplements that cause negative health issues when taken with cephalexin. But experts say many of these side effects are unlikely, and some are more common than others. A big one to be aware of: If you’re taking the diabetes drug metformin, which lowers blood sugar levels, cephalexin can be a problem, says Alia Aaeedy, the director of pharmacy at Texas Surgical Hospital in Plano, Texas. “Cephalexin is known to increase the serum levels [i.e. concentration] of metformin,” she says. If you take the two drugs together, you will need blood monitoring since metformin serum levels that are too high can cause your blood sugar to dip dangerously low.

When A Drop Isn't Enough

For adults with soft tissue infections (e.g., preseptal cellulitis, dacryocystitis, dacryoadenitis), our first choice is Keflex (cephalexin, Advancis Pharmaceutical) at a dosage of 250mg to 500 mg QID for 10 to 14 days. Cephalexin is a member of the cephalosporin antibiotic class. These agents demonstrate a similar mode of action and side effect profile as the penicillins. Keflex is a great choice due to cost and proven efficacy. Although Augmentin would be our first choice for pediatric patients, Keflex can also be dosed at 25mg/kg/day to 50mg/kg/day.

Resources

11 Cephalexin (Keflex) Side Effects You Should Know About

The most common cephalexin side effects are diarrhea, nausea, and stomach pain. Headache, fatigue, and vaginal yeast infections can also happen. Serious cephalexin side effects are rare, but possible. They include seizures, infectious diarrhea, and bleeding. Severe allergic reactions can also happen.

Cephalexin

Cephalexin is an antibiotic approved by the U.S. Food and Drug Administration (FDA) in 1970 and is classified as a first-generation cephalosporin. This drug is widely used in outpatient and inpatient healthcare settings due to its favorable safety and efficacy profile. Cephalexin is commonly utilized in the treatment of urinary tract infections, respiratory infections, otitis media, bone infections caused by Staphylococcus aureus or Proteus mirabilis, and skin and soft tissue infections primarily caused by S aureus or Streptococcus pyogenes.